Order Now Product Folder Support & Community Tools & Software Technical Documents LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 LM2734 Thin SOT 1-A Load Step-Down DC/DC Regulator 1 Features 3 Description * * * * * The LM2734 regulator is a monolithic, highfrequency, PWM step-down DC/DC converter in a 6pin Thin SOT package. The device provides all the active functions to provide local DC/DC conversion with fast transient response and accurate regulation in the smallest possible PCB area. 1 * * * * * * * Thin SOT-6 Package 3-V to 20-V Input Voltage Range 0.8-V to 18-V Output Voltage Range 1-A Output Current 550-kHz (LM2734Y) and 1.6-MHz (LM2734X) Switching Frequencies 300-m NMOS Switch 30-nA Shutdown Current 0.8-V, 2% Internal Voltage Reference Internal Soft Start Current-Mode, PWM Operation Thermal Shutdown Create a Custom Design Using the LM2734 With WEBENCH(R) Power Designer 2 Applications * * * * * * * Local Point-of-Load Regulation Core Power in HDDs Set-Top Boxes Battery-Powered Devices USB Powered Devices DSL Modems Notebook Computers With a minimum of external components and online design support through WEBENCH, the LM2734 regulator is easy to use. The ability to drive 1-A loads with an internal 300-m NMOS switch using state-ofthe-art 0.5-m BiCMOS technology results in the best power density available. The world-class control circuitry allows for on-times as low as 13 ns, thus supporting exceptionally high-frequency conversion over the entire 3-V to 20-V input operating range down to the minimum output voltage of 0.8 V. Switching frequency is internally set to 550 kHz (LM2734Y) or 1.6 MHz (LM2734X), allowing the use of extremely small surface-mount inductors and chip capacitors. Even though the operating frequencies are very high, efficiencies up to 90% are easy to achieve. External shutdown is included, featuring an ultra-low standby current of 30 nA. The LM2734 regulator uses current-mode control and internal compensation to provide high-performance regulation over a wide range of operating conditions. Additional features include internal soft-start circuitry to reduce inrush current, pulse-by-pulse current limit, thermal shutdown, and output overvoltage protection. Device Information(1) PART NUMBER LM2734 PACKAGE SOT (6) BODY SIZE (NOM) 2.90 mm x 1.60 mm (1) For all available packages, see the orderable addendum at the end of the datasheet. Typical Application Circuit Efficiency vs Load Current VIN = 5 V, VOUT = 3.3 V D2 VIN BOOST VIN C3 C1 L1 SW VOUT LM2734 ON D1 EN C2 R1 OFF FB GND R2 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com Table of Contents 1 2 3 4 5 6 7 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 1 1 1 2 3 4 6.1 6.2 6.3 6.4 6.5 6.6 4 4 4 4 5 6 Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. Electrical Characteristics........................................... Typical Characteristics .............................................. Detailed Description .............................................. 8 7.1 7.2 7.3 7.4 Overview ................................................................... 8 Functional Block Diagram ......................................... 9 Feature Description................................................... 9 Device Functional Modes........................................ 10 8 Application and Implementation ........................ 11 8.1 Application Information............................................ 11 8.2 Typical Applications ................................................ 14 9 Power Supply Recommendations...................... 29 10 Layout................................................................... 29 10.1 Layout Guidelines ................................................. 29 10.2 Layout Example .................................................... 30 11 Device and Documentation Support ................. 31 11.1 11.2 11.3 11.4 11.5 11.6 11.7 Development Support .......................................... Receiving Notification of Documentation Updates Community Resources.......................................... Third-Party Products Disclaimer ........................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 31 31 31 31 31 31 32 12 Mechanical, Packaging, and Orderable Information ........................................................... 32 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision J (December 2014) to Revision K Page * Deleted automotive content and moved to separate data sheet SNVSB80 ......................................................................... 1 * Added links for Webench ....................................................................................................................................................... 1 * Changed Abs Max FB voltage max. from "-0.3 V" to "3 V" .................................................................................................... 4 Changes from Revision I (April 2013) to Revision J * 2 Page Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section. ................................................................................................. 1 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 5 Pin Configuration and Functions DDC Package 6-Pin SOT-23-THIN Top View BOOST 1 6 SW GND 2 5 VIN FB 3 4 EN Pin Functions PIN I/O DESCRIPTION NAME NO. BOOST 1 I GND 2 GND FB 3 I Feedback pin. Connect FB to the external resistor divider to set output voltage. EN 4 I Enable control input. Logic high enables operation. Do not allow this pin to float or be greater than VIN + 0.3 V. VIN 5 I Input supply voltage. Connect a bypass capacitor to this pin. SW 6 O Output switch. Connects to the inductor, catch diode, and bootstrap capacitor. Boost voltage that drives the internal NMOS control switch. A bootstrap capacitor is connected between the BOOST and SW pins. Signal and Power ground pin. Place the bottom resistor of the feedback network as close as possible to this pin for accurate regulation. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 3 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 6 Specifications 6.1 Absolute Maximum Ratings over operating free-air temperature (unless otherwise noted) (1) (2) MIN MAX VIN -0.5 24 V SW voltage -0.5 24 V Boost voltage -0.5 30 V Boost to SW voltage -0.5 6 V FB voltage -0.5 3 V EN voltage -0.5 VIN + 0.3 V 150 C 260 C 150 C Junction temperature Soldering information reflow peak pkg. temp.(15s) Storage temperature, Tstg (1) (2) -65 UNIT Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. If Military/Aerospace specified devices are required, contact the Texas Instruments Sales Office/ Distributors for availability and specifications. 6.2 ESD Ratings Human body model (HBM), per ANSI/ESDA/JEDEC JS001 (1) VESD Electrostatic discharge (1) VALUE UNIT 2000 V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. 6.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) MIN VIN NOM MAX UNIT 3 20 V SW voltage -0.5 20 V Boost voltage -0.5 25 V Boost to SW voltage 1.6 5.5 V Junction temperature -40 125 C 6.4 Thermal Information LM2734 THERMAL METRIC (1) DDC (SOT-23-THIN) UNIT 6 PINS RJA Junction-to-ambient thermal resistance 158.1 C/W RJC(top) Junction-to-case (top) thermal resistance 46.5 C/W RJB Junction-to-board thermal resistance 29.5 C/W JT Junction-to-top characterization parameter 0.8 C/W JB Junction-to-board characterization parameter 29.2 C/W RJC(bot) Junction-to-case (bottom) thermal resistance n/a C/W (1) 4 For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 6.5 Electrical Characteristics VIN = 5V, VBOOST - VSW = 5V unless otherwise specified. Datasheet min/max specification limits are ensured by design, test, or statistical analysis. PARAMETER TEST CONDITIONS TJ = 25C MIN (1) TYP (2) MIN VFB Feedback Voltage VFB/ VIN Feedback Voltage Line Regulation VIN = 3V to 20V IFB Feedback Input Bias Current Sink/Source Undervoltage Lockout VIN Rising 2.74 Undervoltage Lockout VIN Falling 2.3 2 UVLO 0.800 TJ = -40C to 125C MAX (1) 0.784 TYP MAX 0.816 0.01 250 V 0.44 0.30 1.6 1.2 1.9 LM2734Y 0.55 0.40 0.66 LM2734X 92 85% LM2734Y 96 90% LM2734X 2% LM2734Y 1% RDS(ON) Switch ON Resistance VBOOST - VSW = 3V 300 ICL Switch Current Limit VBOOST - VSW = 3V 1.7 Quiescent Current Switching 1.5 Quiescent Current (shutdown) VEN = 0V 30 LM2734X (50% Duty Cycle) 2.5 3.5 LM2734Y (50% Duty Cycle) 1.0 1.8 Switching Frequency DMAX Maximum Duty Cycle DMIN IQ IBOOST Minimum Duty Cycle Boost Pin Current Shutdown Threshold Voltage VEN Falling Enable Threshold Voltage VEN Rising IEN Enable Pin Current Sink/Source ISW Switch Leakage VEN_TH (1) (2) nA 2.90 LM2734X FSW V %/V 10 UVLO Hysteresis UNIT 0.62 600 1.2 MHz m 2.5 A 2.5 mA nA mA 0.4 1.8 V 10 nA 40 nA Specified to Average Outgoing Quality Level (AOQL). Typicals represent the most likely parametric norm. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 5 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 6.6 Typical Characteristics All curves taken at VIN = 5 V, VBOOST - VSW = 5 V and TA = 25C, unless specified otherwise. 6 Figure 1. Oscillator Frequency vs Temperature - L1 = 4.7 H Figure 2. Oscillator Frequency vs Temperature - L1 = 10 H Figure 3. Current Limit vs Temperature Figure 4. Current Limit vs Temperature VIN = 20 V Figure 5. VFB vs Temperature Figure 6. RDSON vs Temperature Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 Typical Characteristics (continued) All curves taken at VIN = 5 V, VBOOST - VSW = 5 V and TA = 25C, unless specified otherwise. Figure 7. IQ Switching vs Temperature Figure 8. Line Regulation - L1 = 4.7 H VOUT = 1.5 V, IOUT = 500 mA Figure 9. Line Regulation - L1 = 10 H VOUT = 1.5 V, IOUT = 500 mA Figure 10. Line Regulation - L1 = 4.7 H VOUT = 3.3 V, IOUT = 500 mA Figure 11. Line Regulation - L1 = 10 H VOUT = 3.3 V, IOUT = 500 mA Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 7 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 7 Detailed Description 7.1 Overview The LM2734 device is a constant frequency PWM buck regulator IC that delivers a 1-A load current. The regulator has a preset switching frequency of either 550 kHz (LM2734Y) or 1.6 MHz (LM2734X). These high frequencies allow the LM2734 device to operate with small surface-mount capacitors and inductors, resulting in DC/DC converters that require a minimum amount of board space. The LM2734 device is internally compensated, so it is simple to use, and requires few external components. The LM2734 device uses currentmode control to regulate the output voltage. The following operating description of theLM2734 device will refer to the Simplified Block Diagram () and to the waveforms in Figure 12. The LM2734 device supplies a regulated output voltage by switching the internal NMOS control switch at constant frequency and variable duty cycle. A switching cycle begins at the falling edge of the reset pulse generated by the internal oscillator. When this pulse goes low, the output control logic turns on the internal NMOS control switch. During this on-time, the SW pin voltage (VSW) swings up to approximately VIN, and the inductor current (IL) increases with a linear slope. IL is measured by the current-sense amplifier, which generates an output proportional to the switch current. The sense signal is summed with the regulator's corrective ramp and compared to the error amplifier's output, which is proportional to the difference between the feedback voltage and VREF. When the PWM comparator output goes high, the output switch turns off until the next switching cycle begins. During the switch off-time, inductor current discharges through Schottky diode D1, which forces the SW pin to swing below ground by the forward voltage (VD) of the catch diode. The regulator loop adjusts the duty cycle (D) to maintain a constant output voltage. VSW D = TON/TSW VIN SW Voltage TOFF TON 0 t VD IL TSW IPK Inductor Current t 0 Figure 12. LM2734 Waveforms of SW Pin Voltage and Inductor Current 8 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 7.2 Functional Block Diagram VIN VIN Current-Sense Amplifier EN OFF Internal Regulator and Enable Circuit + - BOOST VBOOST Under Voltage Lockout Oscillator CIN D2 Thermal Shutdown Current Limit Output Control Logic Reset Pulse + ISENSE + + Corrective Ramp 0.3: Switch Driver SW OVP Comparator - ON RSENSE Error Signal D 1 + PWM Comparator CBOOST VSW L IL VOUT COUT 0.88V + - R 1 FB Internal Compensation + Error Amplifier + - VREF 0.8V R 2 GND 7.3 Feature Description 7.3.1 Output Overvoltage Protection The overvoltage comparator compares the FB pin voltage to a voltage that is 10% higher than the internal reference Vref. Once the FB pin voltage goes 10% above the internal reference, the internal NMOS control switch is turned off, which allows the output voltage to decrease toward regulation. 7.3.2 Undervoltage Lockout Undervoltage lockout (UVLO) prevents the LM2734 from operating until the input voltage exceeds 2.74 V (typical). The UVLO threshold has approximately 440 mV of hysteresis, so the part will operate until VIN drops below 2.3 V (typical). Hysteresis prevents the part from turning off during power up if VIN is nonmonotonic. 7.3.3 Current Limit The LM2734 uses cycle-by-cycle current limiting to protect the output switch. During each switching cycle, a current limit comparator detects if the output switch current exceeds 1.7 A (typical), and turns off the switch until the next switching cycle begins. 7.3.4 Thermal Shutdown Thermal shutdown limits total power dissipation by turning off the output switch when the IC junction temperature exceeds 165C. After thermal shutdown occurs, the output switch does not turn on until the junction temperature drops to approximately 150C. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 9 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 7.4 Device Functional Modes 7.4.1 Enable Pin / Shutdown Mode The LM2734 has a shutdown mode that is controlled by the enable pin (EN). When a logic low voltage is applied to EN, the part is in shutdown mode and its quiescent current drops to typically 30 nA. Switch leakage adds another 40 nA from the input supply. The voltage at this pin must never exceed VIN + 0.3 V. 7.4.2 Soft Start This function forces VOUT to increase at a controlled rate during start up. During soft start, the error amplifier's reference voltage ramps from 0 V to its nominal value of 0.8 V in approximately 200 s. This forces the regulator output to ramp up in a more linear and controlled fashion, which helps reduce inrush current. Under some circumstances at start-up, an output voltage overshoot may still be observed. This may be due to a large output load applied during start-up. Large amounts of output external capacitance can also increase output voltage overshoot. A simple solution is to add a feed forward capacitor with a value between 470 pf and 1000 pf across the top feedback resistor (R1). See Figure 23 for further detail. 10 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI's customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information 8.1.1 Boost Function Capacitor CBOOST and diode D2 in Figure 13 are used to generate a voltage VBOOST. VBOOST - VSW is the gate drive voltage to the internal NMOS control switch. To properly drive the internal NMOS switch during its on-time, VBOOST needs to be at least 1.6 V greater than VSW. Although the LM2734 device will operate with this minimum voltage, it may not have sufficient gate drive to supply large values of output current. Therefore, it is recommended that VBOOST be greater than 2.5 V above VSW for best efficiency. VBOOST - VSW should not exceed the maximum operating limit of 5.5 V. 5.5 V > VBOOST - VSW > 2.5 V for best performance. VBOOST D2 BOOST VIN VIN LM2734 CIN CBOOST L SW VOUT GND D1 COUT Figure 13. VOUT Charges CBOOST When the LM2734 device starts up, internal circuitry from the BOOST pin supplies a maximum of 20 mA to CBOOST. This current charges CBOOST to a voltage sufficient to turn the switch on. The BOOST pin continues to source current to CBOOST until the voltage at the feedback pin is greater than 0.76 V. There are various methods to derive VBOOST: 1. From the input voltage (VIN) 2. From the output voltage (VOUT) 3. From an external distributed voltage rail (VEXT) 4. From a shunt or series Zener diode In the simplified block diagram of Functional Block Diagram, capacitor CBOOST and diode D2 supply the gatedrive current for the NMOS switch. Capacitor CBOOST is charged via diode D2 by VIN. During a normal switching cycle, when the internal NMOS control switch is off (TOFF) (refer to Figure 12), VBOOST equals VIN minus the forward voltage of D2 (VFD2), during which the current in the inductor (L) forward biases the Schottky diode D1 (VFD1). Therefore, the voltage stored across CBOOST is: VBOOST - VSW = VIN - VFD2 + VFD1 (1) When the NMOS switch turns on (TON), the switch pin rises to: VSW = VIN - (RDSON x IL), (2) forcing VBOOST to rise thus reverse biasing D2. The voltage at VBOOST is then: VBOOST = 2 VIN - (RDSON x IL) - VFD2 + VFD1 (3) which is approximately: 2VIN - 0.4 V (4) Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 11 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com Application Information (continued) for many applications. Thus the gate-drive voltage of the NMOS switch is approximately: VIN - 0.2 V (5) An alternate method for charging CBOOST is to connect D2 to the output as shown in Figure 13. The output voltage should be from 2.5 V and 5.5 V, so that proper gate voltage will be applied to the internal switch. In this circuit, CBOOST provides a gate drive voltage that is slightly less than VOUT. In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged directly from these voltages. If VIN to VOUT are greater than 5.5 V, CBOOST can be charged from VIN or VOUT minus a Zener voltage by placing a Zener diode D3 in series with D2, as shown in Figure 14. When using a series Zener diode from the input, ensure that the regulation of the input supply does not create a voltage that falls outside the recommended VBOOST voltage. (VINMAX - VD3) < 5.5 V (VINMIN - VD3) > 1.6 V (6) (7) D2 D3 VIN VIN CIN BOOST VBOOST CBOOST LM2734 L VOUT SW GND D1 C OUT Figure 14. Zener Reduces Boost Voltage from VIN An alternative method is to place the Zener diode D3 in a shunt configuration as shown in Figure 15. A small 350 mW to 500 mW 5.1-V Zener diode in a SOT or SOD package can be used for this purpose. A small ceramic capacitor such as a 6.3 V, 0.1-F capacitor (C4) should be placed in parallel with the Zener diode. When the internal NMOS switch turns on, a pulse of current is drawn to charge the internal NMOS gate capacitance. The 0.1-F parallel shunt capacitor ensures that the VBOOST voltage is maintained during this time. Resistor R3 should be chosen to provide enough RMS current to the Zener diode (D3) and to the BOOST pin. A recommended choice for the Zener current (IZENER) is 1 mA. The current IBOOST into the BOOST pin supplies the gate current of the NMOS control switch and varies typically according to the following formula for the X version: IBOOST = 0.56 x (D + 0.54) x (VZENER - VD2) mA (8) IBOOST can be calculated for the Y version using the following: IBOOST = 0.22 x (D + 0.54) x (VZENER - VD2) A (9) where D is the duty cycle, VZENER and VD2 are in volts, and IBOOST is in milliamps. VZENER is the voltage applied to the anode of the boost diode (D2), and VD2 is the average forward voltage across D2. Note that this formula for IBOOST gives typical current. For the worst case IBOOST, increase the current by 40%. In that case, the worst case boost current will be: IBOOST-MAX = 1.4 x IBOOST (10) R3 will then be given by: R3 = (VIN - VZENER) / (1.4 x IBOOST + IZENER) (11) For example, using the X-version let VIN = 10 V, VZENER = 5 V, VD2 = 0.7 V, IZENER = 1 mA, and duty cycle D = 50%. Then: IBOOST = 0.56 x (0.5 + 0.54) x (5 - 0.7) mA = 2.5 mA R3 = (10 V - 5 V) / (1.4 x 2.5 mA + 1 mA) = 1.11 k 12 Submit Documentation Feedback (12) (13) Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 Application Information (continued) VZ C4 D2 D3 R3 VIN VIN C IN BOOST VBOOST CBOOST LM2734 L SW VOUT GND D1 COUT Figure 15. Boost Voltage Supplied from the Shunt Zener on VIN Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 13 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 8.2 Typical Applications 8.2.1 LM2734X (1.6 MHz) VBOOST Derived from VIN 5V to 1.5 V/1 A D2 VIN BOOST VIN C3 C1 L1 R3 VOUT SW LM2734 ON D1 EN C2 R1 OFF FB GND R2 Figure 16. LM2734X (1.6 MHz) VBOOST Derived from VIN 5 V to 1.5-V/1-A Schematic 8.2.1.1 Design Requirements Derive charge for VBOOST from the input supply (VIN ). VBOOST - VSW should not exceed the maximum operating limit of 5.5V. 8.2.1.2 Detailed Design Procedure Table 1. Bill of Materials for Figure 16 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734X C1, Input Cap 10 F, 6.3V, X5R TDK C3216X5ROJ106M C2, Output Cap 10 F, 6.3V, X5R TDK C3216X5ROJ106M C3, Boost Cap 0.01 uF, 16V, X7R TDK C1005X7R1C103K D1, Catch Diode 0.3 VF Schottky 1 A, 10 VR ON Semi MBRM110L D2, Boost Diode 1VF @ 50-mA Diode Diodes, Inc. 1N4148W L1 4.7H, 1.7A, TDK VLCF4020T- 4R7N1R2 R1 8.87 k, 1% Vishay CRCW06038871F R2 10.2 k, 1% Vishay CRCW06031022F R3 100 k, 1% Vishay CRCW06031003F 8.2.1.2.1 Custom Design With WEBENCH(R) Tools Click here to create a custom design using the LM2734 device with the WEBENCH(R) Power Designer. 1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements. 2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial. 3. Compare the generated design with other possible solutions from Texas Instruments. The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time pricing and component availability. In most cases, these actions are available: * Run electrical simulations to see important waveforms and circuit performance * Run thermal simulations to understand board thermal performance * Export customized schematic and layout into popular CAD formats * Print PDF reports for the design, and share the design with colleagues Get more information about WEBENCH tools at www.ti.com/WEBENCH. 14 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 8.2.1.2.2 Inductor Selection The Duty Cycle (D) can be approximated quickly using the ratio of output voltage (VO) to input voltage (VIN): VO D= VIN (14) The catch diode (D1) forward voltage drop and the voltage drop across the internal NMOS must be included to calculate a more accurate duty cycle. Calculate D by using the following formula: VO + VD D= VIN + VD - VSW (15) VSW can be approximated by: VSW = IO x RDS(ON) (16) The diode forward drop (VD) can range from 0.3 V to 0.7 V depending on the quality of the diode. The lower VD is, the higher the operating efficiency of the converter. The inductor value determines the output ripple current. Lower inductor values decrease the size of the inductor, but increase the output ripple current. An increase in the inductor value will decrease the output ripple current. The ratio of ripple current (iL) to output current (IO) is optimized when it is set between 0.3 and 0.4 at 1 A. The ratio r is defined as: r= 'iL lO (17) One must also ensure that the minimum current limit (1.2 A) is not exceeded, so the peak current in the inductor must be calculated. The peak current (ILPK) in the inductor is calculated as shown in Equation 18: ILPK = IO + IL/2 (18) If r = 0.5 at an output of 1 A, the peak current in the inductor will be 1.25 A. The minimum specified current limit over all operating conditions is 1.2 A. One can either reduce r to 0.4 resulting in a 1.2-A peak current, or make the engineering judgement that 50 mA over is safe enough with a 1.7-A typical current limit and 6 sigma limits. When the designed maximum output current is reduced, the ratio r can be increased. At a current of 0.1 A, r can be made as high as 0.9. The ripple ratio can be increased at lighter loads because the net ripple is actually quite low, and if r remains constant the inductor value can be made quite large. An equation empirically developed for the maximum ripple ratio at any current less than 2 A is: r = 0.387 x IOUT-0.3667 (19) Note that this is just a guideline. The LM2734 operates at frequencies allowing the use of ceramic output capacitors without compromising transient response. Ceramic capacitors allow higher inductor ripple without significantly increasing output ripple. See Output Capacitor for more details on calculating output voltage ripple. Now that the ripple current or ripple ratio is determined, the inductance is calculated as shown in Equation 20: L= VO + VD IO x r x fS x (1-D) where * * fs is the switching frequency IO is the output current. (20) When selecting an inductor, make sure that it is capable of supporting the peak output current without saturating. Inductor saturation will result in a sudden reduction in inductance and prevent the regulator from operating correctly. Because of the speed of the internal current limit, it necessary to specify the peak current of the inductor only for the required maximum output current. For example, if the designed maximum output current is 0.5 A and the peak current is 0.7 A, then the inductor should be specified with a saturation current limit of >0.7 A. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 15 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com There is no need to specify the saturation or peak current of the inductor at the 1.7-A typical switch current limit. The difference in inductor size is a factor of 5. Because of the operating frequency of the LM2734, ferrite based inductors are preferred to minimize core losses. This presents little restriction because the variety of ferrite based inductors is huge. Lastly, inductors with lower series resistance (DCR) will provide better operating efficiency. For recommended inductors see example circuits. 8.2.1.2.3 Input Capacitor An input capacitor is necessary to ensure that VIN does not drop excessively during switching transients. The primary specifications of the input capacitor are capacitance, voltage, RMS current rating, and ESL (Equivalent Series Inductance). The recommended input capacitance is 10 F, although 4.7 F is sufficient for input voltages below 6 V. The input voltage rating is specifically stated by the capacitor manufacturer. Make sure to check any recommended deratings and also verify if there is any significant change in capacitance at the operating input voltage and the operating temperature. The input capacitor maximum RMS input current rating (IRMS-IN) must be greater than: r2 D x 1-D + 12 IRMS-IN = IO x (21) From Equation 21 from the above equation that maximum RMS capacitor current occurs when D = 0.5. Always calculate the RMS at the point where the duty cycle, D, is closest to 0.5. The ESL of an input capacitor is usually determined by the effective cross sectional area of the current path. A large leaded capacitor will have high ESL and a 0805 ceramic chip capacitor will have very low ESL. At the operating frequencies of the LM2734 device, certain capacitors may have an ESL so large that the resulting impedance (2fL) will be higher than that required to provide stable operation. As a result, surface-mount capacitors are strongly recommended. Sanyo POSCAP, Tantalum or Niobium, Panasonic SP or Cornell Dubilier ESR, and multilayer ceramic capacitors (MLCC) are all good choices for both input and output capacitors and have very low ESL. For MLCCs it is recommended to use X7R or X5R dielectrics. Consult the capacitor manufacturer data sheet to see how rated capacitance varies over operating conditions. 8.2.1.2.4 Output Capacitor The output capacitor is selected based upon the desired output ripple and transient response. The initial current of a load transient is provided mainly by the output capacitor. The output ripple of the converter is: 'VO = 'iL x (RESR + 1 ) 8 x fS x CO (22) When using MLCCs, the ESR is typically so low that the capacitive ripple may dominate. When this occurs, the output ripple will be approximately sinusoidal and 90 phase shifted from the switching action. Given the availability and quality of MLCCs and the expected output voltage of designs using the LM2734 device, there is really no need to review any other capacitor technologies. Another benefit of ceramic capacitors is their ability to bypass high frequency noise. A certain amount of switching edge noise will couple through parasitic capacitances in the inductor to the output. A ceramic capacitor will bypass this noise while a tantalum will not. Because the output capacitor is one of the two external components that control the stability of the regulator control loop, most applications will require a minimum at 10 F of output capacitance. Capacitance can be increased significantly with little detriment to the regulator stability. Like the input capacitor, recommended multilayer ceramic capacitors are X7R or X5R. Again, verify actual capacitance at the desired operating voltage and temperature. Check the RMS current rating of the capacitor. The RMS current rating of the capacitor chosen must also meet the following condition: IRMS-OUT = IO x r 12 (23) 8.2.1.2.5 Catch Diode The catch diode (D1) conducts during the switch off-time. A Schottky diode is recommended for its fast switching times and low forward voltage drop. The catch diode should be chosen so that its current rating is greater than: ID1 = IO x (1-D) 16 (24) Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 The reverse breakdown rating of the diode must be at least the maximum input voltage plus appropriate margin. To improve efficiency choose a Schottky diode with a low forward voltage drop. 8.2.1.2.6 Boost Diode A standard diode such as the 1N4148 type is recommended. For VBOOST circuits derived from voltages less than 3.3 V, a small-signal Schottky diode is recommended for greater efficiency. A good choice is the BAT54 small signal diode. 8.2.1.2.7 Boost Capacitor A ceramic 0.01-F capacitor with a voltage rating of at least 16 V is sufficient. The X7R and X5R MLCCs provide the best performance. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 17 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 8.2.1.2.8 Output Voltage The output voltage is set using the following equation where R2 is connected between the FB pin and GND, and R1 is connected between VO and the FB pin. A good value for R2 is 10 k. R1 = VO VREF - 1 x R2 (25) 8.2.1.3 Application Curves 18 Figure 17. Efficiency vs Load Current - L1 = 4.7 H VOUT = 5V Figure 18. Efficiency vs Load Current - L1 = 10 H VOUT = 5 V Figure 19. Efficiency vs Load Current - L1 = 4.7 H VOUT = 3.3 V Figure 20. Efficiency vs Load Current - L1 = 10 H VOUT = 3.3 V Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 Figure 21. Efficiency vs Load Current - L1 = 4.7 H VOUT = 1.5 V Figure 22. Efficiency vs Load Current - L1 = 10 H VOUT = 1.5 V Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 19 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 8.2.2 LM2734X (1.6 MHz) VBOOST Derived from VOUT 12 V to 3.3 V /1 A D2 VIN 12V BOOST VIN C3 C1 R3 L1 VOUT 3.3V SW LM2734 D1 C2 ON EN R1 CFF OFF FB GND R2 Figure 23. LM2734X (1.6 MHz) VBOOST Derived from VOUT 12 V to 3.3 V /1-A Schematic 8.2.2.1 Design Requirements Derive charge for VBOOST from the output voltage, (VOUT). The output voltage should be between 2.5 V and 5.5 V. 8.2.2.2 Detailed Design Procedure See Detailed Design Procedure. Table 2. Bill of Materials for Figure 23 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734X C1, Input Cap 10 F, 25 V, X7R TDK C3225X7R1E106M C2, Output Cap 22 F, 6.3 V, X5R TDK C3216X5ROJ226M C3, Boost Cap 0.01 F, 16 V, X7R TDK C1005X7R1C103K CFF 1000 pF 25 V TDK C0603X5R1E102K D1, Catch Diode 0.34 VF Schottky 1 A, 30 VR Vishay SS1P3L D2, Boost Diode 1 VF @ 50-mA Diode Diodes, Inc. 1N4148W L1 4.7H, 1.7 A TDK VLCF4020T- 4R7N1R2 R1 31.6 k, 1% Vishay CRCW06033162F R2 10 k, 1% Vishay CRCW06031002F R3 100 k, 1% Vishay CRCW06031003F 8.2.2.3 Application Curves See Application Curves. 20 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 8.2.3 LM2734X (1.6 MHz) VBOOST Derived from VSHUNT 18 V to 1.5 V /1 A C4 D3 R4 D2 BOOST VIN VIN C3 C1 R3 L1 VOUT SW LM2734 ON D1 C2 EN OFF R1 FB GND R2 Figure 24. LM2734X (1.6 MHz) VBOOST Derived from VSHUNT 18 V to 1.5 V /1-A Schematic 8.2.3.1 Design Requirements An alternative method when VIN is greater than 5.5 V is to place the zener diode D3 in a shunt configuration. A small 350 mW to 500 mW 5.1 V zener in a SOT or SOD package can be used for this purpose. A small ceramic capacitor such as a 6.3 V, 0.1 F capacitor (C4) should be placed in parallel with the zener diode. When the internal NMOS switch turns on, a pulse of current is drawn to charge the internal NMOS gate capacitance. The 0.1 F parallel shunt capacitor ensures that the VBOOST voltage is maintained during this time. 8.2.3.2 Detailed Design Procedure See Detailed Design Procedure. Table 3. Bill of Materials for Figure 24 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734X C1, Input Cap 10 F, 25 V, X7R TDK C3225X7R1E106M C2, Output Cap 22 F, 6.3 V, X5R TDK C3216X5ROJ226M C3, Boost Cap 0.01 F, 16 V, X7R TDK C1005X7R1C103K C4, Shunt Cap 0.1 F, 6.3 V, X5R TDK C1005X5R0J104K D1, Catch Diode 0.4 VF Schottky 1 A, 30 VR Vishay SS1P3L D2, Boost Diode 1 VF @ 50-mA Diode Diodes, Inc. 1N4148W D3, Zener Diode 5.1 V 250 Mw SOT Vishay BZX84C5V1 L1 6.8 H, 1.6 A, TDK SLF7032T-6R8M1R6 R1 8.87 k, 1% Vishay CRCW06038871F R2 10.2 k, 1% Vishay CRCW06031022F R3 100 k, 1% Vishay CRCW06031003F R4 4.12 k, 1% Vishay CRCW06034121F 8.2.3.3 Application Curves See Application Curves. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 21 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 8.2.4 LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1 A D3 D2 BOOST VIN VIN C1 C3 R3 L1 VOUT SW LM2734 ON D1 EN C2 R1 OFF FB GND R2 Figure 25. LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1-A Schematic 8.2.4.1 Design Requirements In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged directly from these voltages. If VIN is greater than 5.5 V, CBOOST can be charged from VIN minus a zener voltage by placing a zener diode D3 in series with D2. When using a series zener diode from the input, ensure that the regulation of the input supply doesn't create a voltage that falls outside the recommended VBOOST voltage. (VINMAX - VD3) < 5.5 V (VINMIN - VD3) > 1.6 V (26) (27) 8.2.4.2 Detailed Design Procedure See Detailed Design Procedure. Table 4. Bill of Materials for Figure 25 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734X C1, Input Cap 10 F, 25V, X7R TDK C3225X7R1E106M C2, Output Cap 22 F, 6.3 V, X5R TDK C3216X5ROJ226M C3, Boost Cap 0.01 F, 16 V, X7R TDK C1005X7R1C103K D1, Catch Diode 0.4 VF Schottky 1 A, 30 VR Vishay SS1P3L D2, Boost Diode 1 VF @ 50-mA Diode Diodes, Inc. 1N4148W D3, Zener Diode 11 V 350 Mw SOT Diodes, Inc. BZX84C11T L1 6.8 H, 1.6 A, TDK SLF7032T-6R8M1R6 R1 8.87 k, 1% Vishay CRCW06038871F R2 10.2 k, 1% Vishay CRCW06031022F R3 100 k, 1% Vishay CRCW06031003F 8.2.4.3 Application Curves See Application Curves. 22 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 8.2.5 LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VOUT) 15 V to 9 V /1 A D3 D2 VIN BOOST VIN C3 C1 R3 L1 VOUT SW LM2734 ON D1 EN C2 R1 OFF FB GND R2 Figure 26. LM2734X (1.6 MHz) VBOOST Derived from Series Zener Diode (VOUT) 15 V to 9 V /1-A Schematic 8.2.5.1 Design Requirements In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged directly from these voltages. If VIN and VOUT are greater than 5.5 V, CBOOST can be charged from VOUT minus a zener voltage by placing a zener diode D3 in series with D2. 8.2.5.2 Detailed Design Procedure See Detailed Design Procedure. Table 5. Bill of Materials for Figure 26 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734X C1, Input Cap 10 F, 25 V, X7R TDK C3225X7R1E106M C2, Output Cap 22 F, 16 V, X5R TDK C3216X5R1C226M C3, Boost Cap 0.01 F, 16 V, X7R TDK C1005X7R1C103K D1, Catch Diode 0.4 VF Schottky 1 A, 30 VR Vishay SS1P3L D2, Boost Diode 1 VF @ 50-mA Diode Diodes, Inc. 1N4148W D3, Zener Diode 4.3 V 350-mw SOT Diodes, Inc. BZX84C4V3 L1 6.8 H, 1.6 A, TDK SLF7032T-6R8M1R6 R1 102 k, 1% Vishay CRCW06031023F R2 10.2 k, 1% Vishay CRCW06031022F R3 100 k, 1% Vishay CRCW06031003F 8.2.5.3 Application Curves See Application Curves. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 23 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 8.2.6 LM2734Y (550 kHz) VBOOST Derived from VIN 5 V to 1.5 V / 1 A D2 VIN BOOST VIN C3 C1 L1 R3 VOUT SW LM2734 ON D1 EN C2 R1 OFF FB GND R2 Figure 27. LM2734Y (550 kHz) VBOOST Derived from VIN 5 V to 1.5 V / 1-A Schematic 8.2.6.1 Design Requirements Derive charge for VBOOST from the input supply (VIN ). VBOOST - VSW should not exceed the maximum operating limit of 5.5 V. 8.2.6.2 Detailed Design Procedure See Detailed Design Procedure. Table 6. Bill of Materials for Figure 27 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734Y C1, Input Cap 10 F, 6.3 V, X5R TDK C3216X5ROJ106M C2, Output Cap 22 F, 6.3 V, X5R TDK C3216X5ROJ226M C3, Boost Cap 0.01 F, 16 V, X7R TDK C1005X7R1C103K D1, Catch Diode 0.3 VF Schottky 1 A, 10 VR ON Semi MBRM110L D2, Boost Diode 1 VF @ 50-mA Diode Diodes, Inc. 1N4148W L1 10 H, 1.6 A, TDK SLF7032T-100M1R4 R1 8.87 k, 1% Vishay CRCW06038871F R2 10.2 k, 1% Vishay CRCW06031022F R3 100 k, 1% Vishay CRCW06031003F 8.2.6.3 Application Curves See Application Curves. 24 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 8.2.7 LM2734Y (550 kHz) VBOOST Derived from VOUT 12 V to 3.3 V / 1 A D2 VIN 12V BOOST VIN C3 C1 R3 L1 VOUT 3.3V SW LM2734 D1 C2 ON EN R1 CFF OFF FB GND R2 Figure 28. LM2734Y (550 kHz) VBOOST Derived from VOUT 12 V to 3.3 V / 1 A Schematic 8.2.7.1 Design Requirements Derive charge for VBOOST from the output voltage, (VOUT ). The output voltage should be between 2.5 V and 5.5 V. 8.2.7.2 Detailed Design Procedure See Detailed Design Procedure. Table 7. Bill of Materials for Figure 28 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734Y C1, Input Cap 10 F, 25 V, X7R TDK C3225X7R1E106M C2, Output Cap 22 F, 6.3 V, X5R TDK C3216X5ROJ226M C3, Boost Cap 0.01 F, 16 V, X7R TDK C1005X7R1C103K D1, Catch Diode 0.34 VF Schottky 1 A, 30VR Vishay SS1P3L D2, Boost Diode 0.6 VF @ 30-mA Diode Vishay BAT17 L1 10 H, 1.6 A TDK SLF7032T-100M1R4 R1 31.6 k, 1% Vishay CRCW06033162F R2 10.0 k, 1% Vishay CRCW06031002F R3 100 k, 1% Vishay CRCW06031003F 8.2.7.3 Application Curves See Application Curves. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 25 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 8.2.8 LM2734Y (550 kHz) VBOOST Derived from VSHUNT 18 V to 1.5 V / 1 A C4 D3 R4 D2 BOOST VIN VIN C3 C1 R3 L1 VOUT SW LM2734 ON D1 C2 EN OFF R1 FB GND R2 Figure 29. LM2734Y (550 kHz) VBOOST Derived from VSHUNT 18 V to 1.5 V / 1-A 8.2.8.1 Design Requirements An alternative method when VIN is greater than 5.5 V is to place the zener diode D3 in a shunt configuration. A small 350 mW to 500 mW 5.1 V zener in a SOT or SOD package can be used for this purpose. A small ceramic capacitor such as a 6.3 V, 0.1 F capacitor (C4) should be placed in parallel with the zener diode. When the internal NMOS switch turns on, a pulse of current is drawn to charge the internal NMOS gate capacitance. The 0.1 F parallel shunt capacitor ensures that the VBOOST voltage is maintained during this time. 8.2.8.2 Detailed Design Procedure See Detailed Design Procedure. Table 8. Bill of Materials for Figure 29 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734Y C1, Input Cap 10 F, 25 V, X7R TDK C3225X7R1E106M C2, Output Cap 22 F, 6.3 V, X5R TDK C3216X5ROJ226M C3, Boost Cap 0.01 F, 16 V, X7R TDK C1005X7R1C103K C4, Shunt Cap 0.1 F, 6.3 V, X5R TDK C1005X5R0J104K D1, Catch Diode 0.4 VF Schottky 1 A, 30VR Vishay SS1P3L D2, Boost Diode 1 VF @ 50-mA Diode Diodes, Inc. 1N4148W D3, Zener Diode 5.1 V 250 Mw SOT Vishay BZX84C5V1 L1 15 H, 1.5 A TDK SLF7045T-150M1R5 R1 8.87 k, 1% Vishay CRCW06038871F R2 10.2 k, 1% Vishay CRCW06031022F R3 100 k, 1% Vishay CRCW06031003F R4 4.12 k, 1% Vishay CRCW06034121F 8.2.8.3 Application Curves See Application Curves. 26 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 8.2.9 LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1 A D3 D2 BOOST VIN VIN C1 C3 R3 L1 VOUT SW LM2734 ON D1 EN C2 R1 OFF FB GND R2 Figure 30. LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VIN) 15 V to 1.5 V / 1-A Schematic 8.2.9.1 Design Requirements In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged directly from these voltages. If VIN is greater than 5.5 V, CBOOST can be charged from VIN minus a zener voltage by placing a zener diode D3 in series with D2. When using a series zener diode from the input, ensure that the regulation of the input supply doesn't create a voltage that falls outside the recommended VBOOST voltage. (VINMAX - VD3) < 5.5 V (VINMIN - VD3) > 1.6 V (28) (29) 8.2.9.2 Detailed Design Procedure See Detailed Design Procedure. Table 9. Bill of Materials for Figure 30 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734Y C1, Input Cap 10 F, 25 V, X7R TDK C3225X7R1E106M C2, Output Cap 22 F, 6.3 V, X5R TDK C3216X5ROJ226M C3, Boost Cap 0.01 F, 16 V, X7R TDK C1005X7R1C103K D1, Catch Diode 0.4 VF Schottky 1 A, 30 VR Vishay SS1P3L D2, Boost Diode 1 VF @ 50-mA Diode Diodes, Inc. 1N4148W D3, Zener Diode 11 V 350 Mw SOT Diodes, Inc. BZX84C11T L1 15 H, 1.5 A, TDK SLF7045T-150M1R5 R1 8.87 k, 1% Vishay CRCW06038871F R2 10.2 k, 1% Vishay CRCW06031022F R3 100 k, 1% Vishay CRCW06031003F 8.2.9.3 Application Curves See Application Curves. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 27 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 8.2.10 LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VOUT) 15 V to 9 V / 1 A D3 D2 VIN BOOST VIN C3 C1 R3 L1 VOUT SW LM2734 ON D1 EN C2 R1 OFF FB GND R2 Figure 31. LM2734Y (550 kHz) VBOOST Derived from Series Zener Diode (VOUT) 15 V to 9 V / 1-A 8.2.10.1 Design Requirements In applications where both VIN and VOUT are greater than 5.5 V, or less than 3 V, CBOOST cannot be charged directly from these voltages. If VIN and VOUT are greater than 5.5 V, CBOOST can be charged from VOUT minus a zener voltage by placing a zener diode D3 in series with D2. 8.2.10.2 Detailed Design Procedure See Detailed Design Procedure. Table 10. Bill of Materials for Figure 31 PART ID PART VALUE MANUFACTURER PART NUMBER U1 1-A Buck Regulator Texas Instruments LM2734Y C1, Input Cap 10 F, 25 V, X7R TDK C3225X7R1E106M C2, Output Cap 22 F, 16 V, X5R TDK C3216X5R1C226M C3, Boost Cap 0.0 1 F, 16 V, X7R TDK C1005X7R1C103K D1, Catch Diode 0.4 VF Schottky 1 A, 30 VR Vishay SS1P3L D2, Boost Diode 1 VF @ 50-mA Diode Diodes, Inc. 1N4148W D3, Zener Diode 4.3 V 350 Mw SOT Diodes, Inc. BZX84C4V3 L1 22 H, 1.4 A, TDK SLF7045T-220M1R3-1PF R1 102 k, 1% Vishay CRCW06031023F R2 10.2k, 1% Vishay CRCW06031022F R3 100k, 1% Vishay CRCW06031003F 8.2.10.3 Application Curves See Application Curves. 28 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 9 Power Supply Recommendations Input voltage is rated as 3 V to 18 V; however, care must be taken in certain circuit configurations (for example, VBOOST derived from VIN where the requirement that VBOOST - VSW < 5.5 V should be observed) Also, for best efficiency VBOOST should be at least 2.5-V above VSW. The voltage on the Enable pin should not exceed VIN by more than 0.3 V. 10 Layout 10.1 Layout Guidelines When planning layout there are a few things to consider when trying to achieve a clean, regulated output. The most important consideration when completing the layout is the close coupling of the GND connections of the CIN capacitor and the catch diode D1. These ground ends should be close to one another and be connected to the GND plane with at least two through-holes. Place these components as close to the IC as possible. Next in importance is the location of the GND connection of the COUT capacitor, which should be near the GND connections of CIN and D1. There should be a continuous ground plane on the bottom layer of a two-layer board except under the switching node island. The FB pin is a high-impedance node -- take care to make the FB trace short to avoid noise pickup and inaccurate regulation. The feedback resistors should be placed as close as possible to the IC, with the GND of R2 placed as close as possible to the GND of the IC. The VOUT trace to R1 should be routed away from the inductor and any other traces that are switching. High AC currents flow through the VIN, SW and VOUT traces, so they should be as short and wide as possible. However, making the traces wide increases radiated noise, so the designer must make this trade-off. Radiated noise can be decreased by choosing a shielded inductor. The remaining components should also be placed as close as possible to the IC. See Application Note AN-1229 (SNVA054) for further considerations and the LM2734 demo board as an example of a four-layer layout. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 29 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 10.2 Layout Example Figure 32. Top Layer D2 VIN VIN BOOST C3 C1 R5 L1 VOUT SW D1 VEN C2 R1 EN FB GND R2 Figure 33. Layout Schematic 30 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 LM2734 www.ti.com SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 11 Device and Documentation Support 11.1 Development Support 11.1.1 Custom Design With WEBENCH(R) Tools Click here to create a custom design using the LM2734 device with the WEBENCH(R) Power Designer. 1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements. 2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial. 3. Compare the generated design with other possible solutions from Texas Instruments. The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time pricing and component availability. In most cases, these actions are available: * Run electrical simulations to see important waveforms and circuit performance * Run thermal simulations to understand board thermal performance * Export customized schematic and layout into popular CAD formats * Print PDF reports for the design, and share the design with colleagues Get more information about WEBENCH tools at www.ti.com/WEBENCH. 11.2 Receiving Notification of Documentation Updates To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document. 11.3 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2ETM Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 11.4 Third-Party Products Disclaimer TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE. 11.5 Trademarks E2E is a trademark of Texas Instruments. WEBENCH is a registered trademark of Texas Instruments. All other trademarks are the property of their respective owners. 11.6 Electrostatic Discharge Caution These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 31 LM2734 SNVS288K - SEPTEMBER 2004 - REVISED SEPTEMBER 2018 www.ti.com 11.7 Glossary SLYZ022 -- TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. 32 Submit Documentation Feedback Copyright (c) 2004-2018, Texas Instruments Incorporated Product Folder Links: LM2734 PACKAGE OPTION ADDENDUM www.ti.com 11-Jan-2021 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan (2) Lead finish/ Ball material MSL Peak Temp Op Temp (C) Device Marking (3) (4/5) (6) LM2734XMK/NOPB ACTIVE SOT-23-THIN DDC 6 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SFDB LM2734XMKX/NOPB ACTIVE SOT-23-THIN DDC 6 3000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SFDB LM2734YMK NRND SOT-23-THIN DDC 6 1000 Non-RoHS & Green Call TI Call TI -40 to 125 SFEB LM2734YMK/NOPB ACTIVE SOT-23-THIN DDC 6 1000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SFEB LM2734YMKX/NOPB ACTIVE SOT-23-THIN DDC 6 3000 RoHS & Green SN Level-1-260C-UNLIM -40 to 125 SFEB (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two lines if the finish value exceeds the maximum column width. Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 11-Jan-2021 Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis. OTHER QUALIFIED VERSIONS OF LM2734 : * Automotive: LM2734-Q1 NOTE: Qualified Version Definitions: * Automotive - Q100 devices qualified for high-reliability automotive applications targeting zero defects Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 29-Sep-2019 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) LM2734XMK/NOPB SOT23-THIN DDC 6 1000 178.0 8.4 LM2734XMKX/NOPB SOT23-THIN DDC 6 3000 178.0 LM2734YMK SOT23-THIN DDC 6 1000 LM2734YMK/NOPB SOT23-THIN DDC 6 LM2734YMKX/NOPB SOT23-THIN DDC 6 3.2 3.2 1.4 4.0 8.0 Q3 8.4 3.2 3.2 1.4 4.0 8.0 Q3 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3 1000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3 3000 178.0 8.4 3.2 3.2 1.4 4.0 8.0 Q3 Pack Materials-Page 1 W Pin1 (mm) Quadrant PACKAGE MATERIALS INFORMATION www.ti.com 29-Sep-2019 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2734XMK/NOPB SOT-23-THIN DDC 6 1000 210.0 185.0 35.0 LM2734XMKX/NOPB SOT-23-THIN DDC 6 3000 210.0 185.0 35.0 LM2734YMK SOT-23-THIN DDC 6 1000 210.0 185.0 35.0 LM2734YMK/NOPB SOT-23-THIN DDC 6 1000 210.0 185.0 35.0 LM2734YMKX/NOPB SOT-23-THIN DDC 6 3000 210.0 185.0 35.0 Pack Materials-Page 2 PACKAGE OUTLINE DDC0006A SOT - 1.1 max height SCALE 4.000 SOT 3.05 2.55 1.75 1.45 PIN 1 INDEX AREA 1.100 0.847 B 1 0.1 C A 6 4X 0.95 3.05 2.75 1.9 4 3 0.5 0.3 0.2 0.1 TYP 0.0 6X C 0 -8 TYP 0.20 TYP 0.12 C A B SEATING PLANE 0.6 TYP 0.3 0.25 GAGE PLANE 4214841/B 11/2020 NOTES: 1. All linear dimensions are in millimeters. Any dimensions in parenthesis are for reference only. Dimensioning and tolerancing per ASME Y14.5M. 2. This drawing is subject to change without notice. 3. Reference JEDEC MO-193. www.ti.com EXAMPLE BOARD LAYOUT DDC0006A SOT - 1.1 max height SOT SYMM 6X (1.1) 1 6 6X (0.6) SYMM 4X (0.95) 4 3 (R0.05) TYP (2.7) LAND PATTERN EXAMPLE EXPLOSED METAL SHOWN SCALE:15X SOLDER MASK OPENING METAL UNDER SOLDER MASK METAL SOLDER MASK OPENING EXPOSED METAL EXPOSED METAL 0.07 MIN ARROUND 0.07 MAX ARROUND NON SOLDER MASK DEFINED SOLDER MASK DEFINED SOLDERMASK DETAILS 4214841/B 11/2020 NOTES: (continued) 4. Publication IPC-7351 may have alternate designs. 5. Solder mask tolerances between and around signal pads can vary based on board fabrication site. www.ti.com EXAMPLE STENCIL DESIGN DDC0006A SOT - 1.1 max height SOT SYMM 6X (1.1) 1 6 6X (0.6) SYMM 4X(0.95) 4 3 (R0.05) TYP (2.7) SOLDER PASTE EXAMPLE BASED ON 0.125 THICK STENCIL SCALE:15X 4214841/B 11/2020 NOTES: (continued) 6. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate design recommendations. 7. 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