TO-220 TO-263
WSON
Pin 1. Adjustment/Ground
2. Output
3. Input
Tab is Output
1
1
1
2
3
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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.
LM1086
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LM1086 1.5-A Low Dropout Positive Voltage Regulators
1
1 Features
1• Available in Fixed 1.8-V, 2.5-V, 3.3-V, 5-V
• Available in Adjustable Version
• Current Limiting and Thermal Protection
• 2% Output Accuracy
• Output Current 1.5 A
• Line Regulation 0.015% (Typical)
• Load Regulation 0.1% (Typical)
• Maximum Input Voltage up to 29V
• Minimum Adjustable Output Voltage Down to
1.25V
• Stable with Ceramic Output Capacitor with ESR
• Temperature Range : -40°C to 125°C
2 Applications
• High-Efficiency Linear Regulators
• Battery Chargers
• Post Regulation for Switching Supplies
• Constant Current Regulators
• Microprocessor Supplies
• Audio Amplifiers Supplies
• Fire Alarm Control
3 Description
The LM1086 is a regulator with a maximum dropout
of 1.5 V at 1.5 A of load current. The device has the
same pin-out as TI's industry standard LM317.
Two resistors are required to set the output voltage of
the adjustable output voltage version of the LM1086.
Fixed output voltage versions integrate the adjust
resistors. Typically, no input capacitor is needed
unless the device is situated more than 6 inches from
the input filter capacitors. Output capacitor can be
replaced with ceramic and appropriate ESR.
The LM1086 circuit includes a zener trimmed
bandgap reference, current limiting, and thermal
shutdown. Because the LM1086 regulator is floating
and detects only the input-to-output differential
voltage, supplies of several hundred volts can be
regulated as long as the maximum input-to-output
differential is not exceeded. Exceeding the maximum
input-to-output deferential will result in short-circuiting
the output. By connecting a fixed resistor between the
adjustment pin and output, the LM1086 can be also
used as a precision current regulator.
For applications requiring greater output current, refer
to LM1084 (clickable link) for the 5-A version, and
the LM1085 (clickable link) for the 3-A version.
Device Information(1)
PART NUMBER PACKAGE BODY SIZE (NOM)
LM1086 WSON (8) 4 mm × 4 mm
DDPAK/TO-263 (3) 10.18 mm × 8.41 mm
TO-220 (3) 14.986 mm × 10.16 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
Typical Application
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Table of Contents
1 Features.................................................................. 1
2 Applications ........................................................... 1
3 Description............................................................. 1
4 Revision History..................................................... 2
5 Pin Configuration and Functions......................... 3
6 Specifications......................................................... 4
6.1 Absolute Maximum Ratings ...................................... 4
6.2 ESD Ratings ............................................................ 4
6.3 Recommended Operating Conditions....................... 4
6.4 Thermal Information.................................................. 5
6.5 Electrical Characteristics........................................... 5
6.6 Typical Characteristics.............................................. 7
7 Detailed Description.............................................. 9
7.1 Overview................................................................... 9
7.2 Functional Block Diagram......................................... 9
7.3 Feature Description................................................. 10
7.4 Device Functional Modes........................................ 11
8 Application and Implementation ........................ 13
8.1 Application Information............................................ 13
8.2 Typical Applications ................................................ 13
9 Power Supply Recommendations...................... 18
10 Layout................................................................... 18
10.1 Layout Guidelines ................................................. 18
10.2 Layout Example .................................................... 18
10.3 Thermal Considerations........................................ 19
11 Device and Documentation Support................. 21
11.1 Development Support ........................................... 21
11.2 Trademarks........................................................... 21
11.3 Electrostatic Discharge Caution............................ 21
11.4 Glossary................................................................ 21
12 Mechanical, Packaging, and Orderable
Information........................................................... 21
4 Revision History
Changes from Revision I (August 2014) to Revision J Page
• Added 8-pin WSON pinout drawing and associated device information................................................................................ 3
Changes from Revision H (May 2013) to Revision I 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 ................................................................................................. 4
VIN
N/C
N/C
VOUT
1
3
4
2
6
5
7
8
ADJ/GND
N/C
VOUT
VOUT
VOUT
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5 Pin Configuration and Functions
8-Pin WSON
Package NGN
Top View
3-Pin TO-220
Package NDE
Top View
3-Pin DDPAK/TO-263
Package KTT
Top View
Pin Functions
PIN
I/O DESCRIPTION
NAME NUMBER
KTT/NDE NGN
ADJ/GND 1 1 –– Adjust pin for the adjustable output voltage version. Ground pin for the fixed
output voltage versions.
VOUT 2, TAB 6, 7, 8, PAD O Output voltage pin for the regulator.
VIN 3 2 I Input voltage pin for the regulator.
N/C 3, 4, 5 –– No Connection
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(1) 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.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
(3) Power dissipation is kept in a safe range by current limiting circuitry. Refer to Overload Recovery in Application and Implementation. The
value θJA for the WSON package is specifically dependent on PCB trace area, trace material, and the number of thermal vias. For
improved thermal resistance and power dissipation for the WSON package, refer to Application Note AN-1187 (literature number
SNOA401).
(4) The maximum power dissipation is a function of TJ(MAX) ,θJA, and TA. The maximum allowable power dissipation at any ambient
temperature is PD= (TJ(MAX)–T A)/θJA. All numbers apply for packages soldered directly into a PC board. Refer to Thermal
Considerations
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)(2)
MIN MAX UNIT
Maximum Input to Output Voltage Differential
LM1086-ADJ 29 V
LM1086-1.8 27 V
LM1086-2.5 27 V
LM1086-3.3 27 V
LM1086-5.0 25 V
Power Dissipation(3) Internally Limited
Junction Temperature (TJ)(4) 150 °C
Lead Temperature 260, to 10 sec °C
Storage temperature, Tstg –65 150 °C
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
6.2 ESD Ratings VALUE UNIT
V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2000 V
(1) The maximum power dissipation is a function of TJ(MAX) ,θJA, and TA. The maximum allowable power dissipation at any ambient
temperature is PD= (TJ(MAX)–T A)/θJA. All numbers apply for packages soldered directly into a PC board. Refer to Thermal
Considerations.
6.3 Recommended Operating Conditions MIN MAX UNIT
JUNCTION TEMPERATURE RANGE (TJ)(1)
"C" Grade Control Section 0 125 °C
Output Section 0 150 °C
"I" Grade Control Section −40 125 °C
Output Section −40 150 °C
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(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
6.4 Thermal Information
THERMAL METRIC(1) LM1086
UNITKTT NDE NGN
3 PINS 3 PINS 8 PINS
RθJA Junction-to-ambient thermal resistance 40.8 23.0 35.9
°C/W
RθJC(top) Junction-to-case (top) thermal resistance 42.3 16.1 24.2
RθJB Junction-to-board thermal resistance 23.3 4.5 13.2
ψJT Junction-to-top characterization parameter 10.2 2.4 0.2
ψJB Junction-to-board characterization parameter 22.3 2.5 13.3
RθJC(bot) Junction-to-case (bottom) thermal resistance: Control
Section/Output Section 1.5/4.0 1.5/4.0 2.9
(1) All limits are specified by testing or statistical analysis.
(2) Typical Values represent the most likely parametric norm.
(3) IFULL LOAD is defined in the current limit curves. The IFULL LOAD Curve defines current limit as a function of input-to-output voltage. Note
that 15W power dissipation for the LM1086 is only achievable over a limited range of input-to-output voltage.
(4) Load and line regulation are measured at constant junction temperature, and are specified up to the maximum power dissipation of
15W. Power dissipation is determined by the input/output differential and the output current. Ensured maximum power dissipation will
not be available over the full input/output range.
6.5 Electrical Characteristics
Typicals and limits appearing in normal type apply for TJ= 25°C unless specified otherwise.
PARAMETER TEST CONDITIONS TJ= 25°C
TJover the entire range for
operation (see
Recommended Operating
Conditions)UNIT
MIN TYP MAX MIN(1) TYP(2) MAX (1)
VREF Reference
Voltage
LM1086-ADJ, IOUT = 10 mA,
VIN −VOUT = 3 V, 10 mA ≤
IOUT ≤IFULL LOAD, 1.5 V ≤VIN
−VOUT ≤15 V(3) 1.238 1.250 1.262 1.225 1.250 1.270 V
VOUT Output Voltage(3) LM1086-1.8, IOUT = 0 mA, VIN
= 5 V, 0 ≤IOUT ≤IFULL LOAD,
3.3 V ≤VIN ≤18 V 1.782 1.8 1.818 1.764 1.8 1.836 V
LM1086-2.5, IOUT = 0 mA, VIN
= 5 V, 0 ≤IOUT ≤IFULL LOAD,
4.0 V ≤VIN ≤18 V 2.475 2.50 2.525 2.450 2.50 2.55 V
LM1086-3.3, IOUT = 0 mA, VIN
= 5 V, 0 ≤IOUT ≤IFULL LOAD,
4.75 V ≤VIN ≤18 V 3.267 3.300 3.333 3.235 3.300 3.365 V
LM1086-5.0, IOUT = 0 mA, VIN
= 8 V, 0 ≤IOUT ≤IFULL LOAD,
6.5 V ≤VIN ≤20 V 4.950 5.000 5.050 4.900 5.000 5.100 V
ΔVOUT Line
Regulation(4)
LM1086-ADJ, IOUT =10 mA,
1.5 V ≤(VIN - VOUT)≤15 V 0.015% 0.2% 0.035% 0.2%
LM1086-1.8, IOUT = 0 mA, 3.3
V≤VIN ≤18 V 0.3 6 0.6 6 mV
LM1086-2.5, IOUT = 0 mA, 4.0
V≤VIN ≤18 V 0.3 6 0.6 6 mV
LM1086-3.3, IOUT = 0 mA, 4.5
V≤VIN ≤18 V 0.5 10 1.0 10 mV
LM1086-5.0, IOUT = 0 mA, 6.5
V≤VIN ≤20 V 0.5 10 1.0 10 mV
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Electrical Characteristics (continued)
Typicals and limits appearing in normal type apply for TJ= 25°C unless specified otherwise.
PARAMETER TEST CONDITIONS TJ= 25°C
TJover the entire range for
operation (see
Recommended Operating
Conditions)UNIT
MIN TYP MAX MIN(1) TYP(2) MAX (1)
(5) Dropout voltage is specified over the full output current range of the device.
(6) The minimum output current required to maintain regulation.
ΔVOUT Load
Regulation(4)
LM1086-ADJ, (VIN-V OUT )=3
V, 10 mA ≤IOUT ≤IFULL LOAD 0.1% 0.3% 0.2% 0.4%
LM1086-1.8, 2.5, VIN = 5 V, 0
≤IOUT ≤IFULL LOAD 3 12 6 20 mV
LM1086-3.3, VIN = 5 V, 0 ≤
IOUT ≤IFULL LOAD 3 15 7 25 mV
LM1086-5.0, VIN = 8 V, 0 ≤
IOUT ≤IFULL LOAD 5 20 10 35 mV
Dropout
Voltage(5) LM1086-ADJ, 1.8, 2.5, 3.3, 5,
ΔVREF,ΔVOUT = 1%, IOUT =
1.5A 1.3 1.5 V
ILIMIT Current Limit
LM1086-ADJ, VIN −VOUT = 5
V, VIN −VOUT = 25 V 1.50 2.7 A
0.05 0.15
LM1086-1.8,2.5, 3.3, VIN = 8
V1.5 2.7 A
LM1086-5.0, VIN = 10 V 1.5 2.7 A
Minimum Load
Current(6) LM1086-ADJ, VIN −VOUT = 25
V5.0 10.0 mA
Quiescent
Current
LM1086-1.8, 2.5, VIN ≤18 V 5.0 10.0 mA
LM1086-3.3, VIN ≤18 V 5.0 10.0 mA
LM1086-5.0, VIN ≤20 V 5.0 10.0 mA
Thermal
Regulation TA= 25°C, 30ms Pulse 0.008 0.04 %/W
Ripple Rejection
fRIPPLE = 120 Hz, COUT = 25
µF Tantalum, IOUT = 1.5 A
60 75
dB
LM1086-ADJ, CADJ = 25 µF,
(VIN−VO) = 3 V
LM1086-1.8, 2.5, VIN = 6 V 60 72 dB
LM1086-3.3, VIN= 6.3 V 60 72 dB
LM1086-5.0 VIN = 8 V 60 68 dB
Adjust Pin
Current LM1086 55 120 µA
Adjust Pin
Current Change 10 mA ≤IOUT ≤IFULL LOAD, 1.5
V≤(VIN−VOUT)≤15 V 0.2 5 µA
Temperature
Stability 0.5%
Long Term
Stability TA= 125°C, 1000 Hrs 0.3% 1.0%
RMS Noise
(% of VOUT)10 Hz ≤f≤10 kHz 0.003%
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6.6 Typical Characteristics
Figure 1. Dropout Voltage vs Output Current Figure 2. Short-Circuit Current vs Input/Output Difference
Figure 3. Load Regulation vs Temperature Figure 4. Percent Change in Output Voltage vs Temperature
Figure 5. Adjust Pin Current vs Temperature Figure 6. Maximum Power Dissipation vs Temperature
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Typical Characteristics (continued)
Figure 7. Ripple Rejection vs Frequency (LM1086-ADJ) Figure 8. Ripple Rejection vs Output Current (LM1086-ADJ)
Figure 9. Ripple Rejection vs Frequency (LM1086-5) Figure 10. Ripple Rejection vs Output Current (LM1086-5)
Figure 11. Line Transient Response Figure 12. Load Transient Response
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7 Detailed Description
7.1 Overview
A basic functional diagram for the LM1086-ADJ (excluding protection circuitry) is shown in Figure 13. The
topology is basically that of the LM317 except for the pass transistor. Instead of a Darlingtion NPN with its two
diode voltage drop, the LM1086 uses a single NPN. This results in a lower dropout voltage. The structure of the
pass transistor is also known as a quasi LDO. The advantage of a quasi LDO over a PNP LDO is its inherently
lower quiescent current. The LM1086 is specified to provide a minimum dropout voltage of 1.5V over
temperature, at full load.
Figure 13. Basic Functional Block Diagram
7.2 Functional Block Diagram
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7.3 Feature Description
7.3.1 Ripple Rejection
Ripple rejection is a function of the open loop gain within the feed-back loop (refer to Figure 13 and Figure 16).
The LM1086 exhibits 75dB of ripple rejection (typ.). When adjusted for voltages higher than VREF, the ripple
rejection decreases as function of adjustment gain: (1+R1/R2) or VO/VREF. Therefore a 5-V adjustment decreases
ripple rejection by a factor of four (−12dB); Output ripple increases as adjustment voltage increases.
However, the adjustable version allows this degradation of ripple rejection to be compensated. The adjust
terminal can be bypassed to ground with a capacitor (CADJ). The impedance of the CADJ should be equal to or
less than R1 at the desired ripple frequency. This bypass capacitor prevents ripple from being amplified as the
output voltage is increased.
1/(2π*fRIPPLE*CADJ)≤R1(1)
7.3.2 Load Regulation
The LM1086 regulates the voltage that appears between its output and ground pins, or between its output and
adjust pins. In some cases, line resistances can introduce errors to the voltage across the load. To obtain the
best load regulation, a few precautions are needed.
Figure 14 shows a typical application using a fixed output regulator. Rt1 and Rt2 are the line resistances. VLOAD
is less than the VOUT by the sum of the voltage drops along the line resistances. In this case, the load regulation
seen at the RLOAD would be degraded from the data sheet specification. To improve this, the load should be tied
directly to the output terminal on the positive side and directly tied to the ground terminal on the negative side.
Figure 14. Typical Application Using Fixed Output Regulator
When the adjustable regulator is used (Figure 15), the best performance is obtained with the positive side of the
resistor R1 tied directly to the output terminal of the regulator rather than near the load. This eliminates line drops
from appearing effectively in series with the reference and degrading regulation. For example, a 5V regulator with
0.05-Ωresistance between the regulator and load will have a load regulation due to line resistance of 0.05 Ω× IL.
If R1 (=125 Ω) is connected near the load the effective line resistance will be 0.05 Ω(1 + R2/R1) or in this case,
it is 4 times worse. In addition, the ground side of the resistor R2 can be returned near the ground of the load to
provide remote ground sensing and improve load regulation.
Figure 15. Best Load Regulation Using Adjustable Output Regulator
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Feature Description (continued)
7.3.3 Overload Recovery
Overload recovery refers to regulator's ability to recover from a short circuited output. A key factor in the recovery
process is the current limiting used to protect the output from drawing too much power. The current limiting circuit
reduces the output current as the input to output differential increases. Refer to short circuit curve in the Typical
Characteristics section.
During normal start-up, the input to output differential is small since the output follows the input. But, if the output
is shorted, then the recovery involves a large input to output differential. Sometimes during this condition the
current limiting circuit is slow in recovering. If the limited current is too low to develop a voltage at the output, the
voltage will stabilize at a lower level. Under these conditions it may be necessary to recycle the power of the
regulator in order to get the smaller differential voltage and thus adequate start up conditions. Refer to Typical
Characteristics section for the short circuit current vs. input differential voltage.
7.4 Device Functional Modes
7.4.1 Output Voltage
The LM1086 adjustable version develops a 1.25-V reference voltage, (VREF), between the output and the adjust
terminal. As shown in Figure 16, this voltage is applied across resistor R1 to generate a constant current I1. This
constant current then flows through R2. The resulting voltage drop across R2 adds to the reference voltage to
sets the desired output voltage.
The current IADJ from the adjustment terminal introduces an output error . But since it is small (120uA max), it
becomes negligible when R1 is in the 100 Ωrange.
For fixed voltage devices, R1 and R2 are integrated inside the devices.
Figure 16. Basic Adjustable Regulator
7.4.2 Stability Consideration
Stability consideration primarily concerns the phase response of the feedback loop. In order for stable operation,
the loop must maintain negative feedback. The LM1086 requires a certain amount series resistance with
capacitive loads. This series resistance introduces a zero within the loop to increase phase margin and thus
increase stability. The equivalent series resistance (ESR) of solid tantalum or aluminum electrolytic capacitors is
used to provide the appropriate zero (approximately 500 kHz).
Aluminum electrolytics are less expensive than tantalums, but their ESR varies exponentially at cold
temperatures; therefore requiring close examination when choosing the desired transient response over
temperature. Tantalums are a convenient choice because their ESR varies less than 2:1 over temperature.
The recommended load/decoupling capacitance is a 10 uF tantalum or a 50 uF aluminum. These values will
assure stability for the majority of applications.
The adjustable versions allows an additional capacitor to be used at the ADJ pin to increase ripple rejection. If
this is done the output capacitor should be increased to 22uF for tantalum or to 150 uF for aluminum.
Capacitors other than tantalum or aluminum can be used at the adjust pin and the input pin. A 10 uF capacitor is
a reasonable value at the input. See Ripple Rejection section regarding the value for the adjust pin capacitor.
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Device Functional Modes (continued)
It is desirable to have large output capacitance for applications that entail large changes in load current
(microprocessors for example). The higher the capacitance, the larger the available charge per demand. It is also
desirable to provide low ESR to reduce the change in output voltage:
ΔV = ΔI x ESR (2)
It is common practice to use several tantalum and ceramic capacitors in parallel to reduce this change in the
output voltage by reducing the overall ESR.
Output capacitance can be increased indefinitely to improve transient response and stability.
7.4.3 Protection Diodes
Under normal operation, the LM1086 regulator does not need any protection diode. With the adjustable device,
the internal resistance between the adjustment and output terminals limits the current. No diode is needed to
divert the current around the regulator even with a capacitor on the adjustment terminal. The adjust pin can take
a transient signal of ±25 V with respect to the output voltage without damaging the device.
When an output capacitor is connected to a regulator and the input is shorted, the output capacitor will discharge
into the output of the regulator. The discharge current depends on the value of the capacitor, the output voltage
of the regulator, and rate of decrease of VIN. In the LM1086 regulator, the internal diode between the output and
input pins can withstand microsecond surge currents of 10 A to 20 A. With an extremely large output capacitor
(≥1000 µf), and with input instantaneously shorted to ground, the regulator could be damaged. In this case, an
external diode is recommended between the output and input pins to protect the regulator, shown in Figure 17.
Figure 17. Regulator with Protection Diode
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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
The LM1086 is versatile in its applications, including uses in programmable output regulation and local on-card
regulation. Or, by connecting a fixed resistor between the ADJUST and OUTPUT terminals, the LM1086 can
function as a precision current regulator. An optional output capacitor can be added to improve transient
response. The ADJUST terminal can be bypassed to achieve very high ripple-rejection ratios, which are difficult
to achieve with standard three-terminal regulators. Please note, in the following applications, if ADJ is mentioned,
it makes use of the adjustable version of the part, however, if GND is mentioned, it is the fixed voltage version of
the part.
8.2 Typical Applications
8.2.1 1.2-V to 15-V Adjustable Regulator
This part can be used as a simple low drop out regulator to enable a variety of output voltages needed for
demanding applications. By using an adjustable R2 resistor a variety of output voltages can be made possible as
shown in Figure 18 based on the LM1086-ADJ.
Figure 18. 1.2-V to 15-V Adjustable Regulator
8.2.1.1 Design Requirements
The device component count is very minimal, employing two resistors as part of a voltage divider circuit and an
output capacitor for load regulation.
8.2.1.2 Detailed Design Procedure
The voltage divider for this part is set based on the equation shown in Figure 18, where R1 is the upper feedback
resistor R2 is the lower feedback resistor.
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Typical Applications (continued)
8.2.1.3 Application Curve
8.2.2 Adjustable at 5 V
The application shown in Figure 19 outlines a simple 5-V output application made possible by the LM1086-ADJ.
This application can provide 1.5 A at high efficiencies and very low drop-out.
Figure 19. Adjustable at 5 V
8.2.3 5-V Regulator with Shutdown
A variation of the 5-V output regulator application with shutdown control is shown in Figure 20 based on the
LM1086-ADJ. It uses a simple NPN transistor on the ADJ pin to block or sink the current on the ADJ pin. If the
TTL logic is pulled high, the NPN transistor is activated and the part is disabled, outputting approximately 1.25 V.
If the TTL logic is pulled low, the NPN transistor is unbiased and the regulator functions normally.
Figure 20. 5-V Regulator with Shutdown
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Typical Applications (continued)
8.2.4 Battery Charger
The LM1086-ADJ can be used as a battery charger to regulate the charging current required by the battery bank
as shown in Figure 21. In this application the LM1086 acts as a constant voltage, constant current part by
sensing the voltage potential across the battery and compensating it to the current voltage. To maintain this
voltage, the regulator delivers the maximum charging current required to charge the battery. As the battery
approaches the fully charged state, the potential drop across the sense resistor, RSreduces and the regulator
throttles back the current to maintain the float voltage of the battery.
Figure 21. Battery Charger
8.2.5 Adjustable Fixed Regulator
A simple adjustable, fixed range output regulator can be made possible by placing a variable resistor on the
ground of the device as shown in Figure 22 based on the fixed output voltage LM1086-5.0. The GND pin has a
small quiescent current of 5 mA typical. Increasing the resistance on the GND pin increases the voltage potential
across the resistor. This potential is then mirrored on to the output to increase the total output voltage by the
potential drop across the GND resistor.
Figure 22. Adjustable Fixed Regulator
8.2.6 Regulator With Reference
A fixed output voltage version of the LM1086-5.0 can be employed to provide an output rail and a reference rail
at the same time as shown in Figure 23. This simple application makes use of a reference diode, the LM136-5,
to regulate the GND voltage to a fixed 5 V based on the quiescent current generated by the GND pin. This
voltage is then added onto the output to generate a total of 10 V out.
Figure 23. Regulator With Reference
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Typical Applications (continued)
8.2.7 High Current Lamp Driver Protection
A simple constant current source with protection can be designed by controlling the impedance between the
lamp and ground. The LM1086-ADJ shown in Figure 24 makes use of an external TTL or CMOS input to drive
the NPN transistor. This pulls the output of the regulator to a few tenths of a volt and puts the part into current
limit. Releasing the logic will reduce the current flow across the lamp into the normal operating current thereby
protecting the lamp during startup.
Figure 24. High Current Lamp Driver Protection
8.2.8 Battery Backup Regulated Supply
A regulated battery backup supply can be generated by using two fixed output voltage versions of the part as
shown in Figure 25. The top regulator supplies the Line voltage during normal operation, however when the input
is not available, the second regulator derives power from the battery backup and regulates it to 5 V based on the
LM1086-5.0. The diodes prevent the rails from back feeding into the supply and batteries.
Figure 25. Battery Backup Regulated Supply
17
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Typical Applications (continued)
8.2.9 Ripple Rejection Enhancement
A very simple ripple rejection circuit is shown in Figure 26 using the LM1086-ADJ. The capacitor C1 smooths out
the ripple on the output by cleaning up the feedback path and preventing excess noise from feeding back into the
regulator. Please remember XC1 should be approximately equal to R1 at the ripple frequency.
Figure 26. Ripple Rejection Enhancement
8.2.10 Automatic Light Control
A common street light control or automatic light control circuit is designed in Figure 27 based on the LM1086-
ADJ. The photo transistor conducts in the presence of light and grounds the ADJ pin preventing the lamp from
turning on. However, in the absence of light, the LM1086 regulates the voltage to 1.25 V between OUT and ADJ,
ensuring the lamp remains on.
Figure 27. Automatic Light Control
8.2.11 Remote Sensing
Remote sensing is a method of compensating the output voltage to a very precise degree by sensing the output
and feeding it back through the feedback. The circuit implementing this is shown in Figure 28 using the LM1086-
ADJ. The output of the regulator is fed into a voltage follower to avoid any loading effects and the output of the
op-amp is injected into the top of the feedback resistor network. This has the effect of modulating the voltage to a
precise degree without additional loading on the output.
Figure 28. Remote Sensing
18
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9 Power Supply Recommendations
The linear regulator input supply should be well regulated and kept at a voltage level such that the maximum
input to output voltage differential allowed by the device is not exceeded. The minimum dropout voltage (VIN –
VOUT) should be met with extra headroom when possible in order to keep the output well regulated. A 10 μF or
higher capacitor should be placed at the input to bypass noise.
10 Layout
10.1 Layout Guidelines
For the best overall performance, some layout guidelines should be followed. Place all circuit components on the
same side of the circuit board and as near as practical to the respective linear regulator pins connections. Traces
should be kept short and wide to reduce the amount of parasitic elements into the system. The actual width and
thickness of traces will depend on the current carrying capability and heat dissipation required by the end
system. An array of plated vias can be placed on the pad area underneath the TAB to conduct heat to any inner
plane areas or to a bottom-side copper plane.
10.2 Layout Example
Figure 29. Layout Example
19
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10.3 Thermal Considerations
ICs heats up when in operation, and power consumption is one factor in how hot it gets. The other factor is how
well the heat is dissipated. Heat dissipation is predictable by knowing the thermal resistance between the IC and
ambient (θJA). Thermal resistance has units of temperature per power (C/W). The higher the thermal resistance,
the hotter the IC.
The LM1086 specifies the thermal resistance for each package as junction to case (θJC). In order to get the total
resistance to ambient (θJA), two other thermal resistance must be added, one for case to heat-sink (θCH) and one
for heatsink to ambient (θHA). The junction temperature can be predicted as follows:
TJ= TA+ PD(θJC +θCH +θHA)=TA+ PDθJA
where
• TJis junction temperature
• TAis ambient temperature
• PDis the power consumption of the device (3)
Device power consumption is calculated as follows:
IIN = IL+ IG(4)
PD= (VIN−VOUT) IL+ VINIG(5)
Figure 30 shows the voltages and currents which are present in the circuit.
Figure 30. Power Dissipation Diagram
Once the devices power is determined, the maximum allowable (θJA (max)) is calculated as:
θJA (max) = TR(max)/PD= TJ(max) −TA(max)/PD
The LM1086 has different temperature specifications for two different sections of the IC: the control section and
the output section. The Thermal Information table shows the junction to case thermal resistances for each of
these sections, while the maximum junction temperatures (TJ(max)) for each section is listed in the Absolute
Maximum Ratings section of the datasheet. TJ(max) is 125°C for the control section, while TJ(max) is 150°C for the
output section.
θJA (max) should be calculated separately for each section as follows:
θJA (max, CONTROL SECTION) = (125°C - TA(max))/PD(6)
θJA (max, OUTPUT SECTION) = (150°C - TA(max))/PD(7)
The required heat sink is determined by calculating its required thermal resistance (θHA (max)).
θHA (max) =θJA (max) −(θJC +θCH) (8)
(θHA (max)) should also be calculated twice as follows:
(θHA (max)) = θJA (max, CONTROL SECTION) - (θJC (CONTROL SECTION) + θCH) (9)
(θHA (max)) = θJA(max, OUTPUT SECTION) - (θJC (OUTPUT SECTION) + θCH) (10)
If thermal compound is used, θCH can be estimated at 0.2 C/W. If the case is soldered to the heat sink, then a
θCH can be estimated as 0 C/W.
After, θHA (max) is calculated for each section, choose the lower of the two θHA (max) values to determine the
appropriate heat sink.
20
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Thermal Considerations (continued)
If PC board copper is going to be used as a heat sink, then Figure 31 can be used to determine the appropriate
area (size) of copper foil required.
Figure 31. Heat Sink Thermal Resistance vs Area
21
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11 Device and Documentation Support
11.1 Development Support
For additional information, see Texas Instruments' E2E community resources at http://e2e.ti.com.
11.2 Trademarks
All trademarks are the property of their respective owners.
11.3 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.
11.4 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.
www.ti.com
PACKAGE OUTLINE
C
1.40
1.14
1.68
1.14
6.22 MIN
2X 2.54
3X 1.40
1.14
15.88
14.60
3X 0.91
0.66
4.83
4.06
0.25
0.00
0.25
GAGE PLANE
6.6 MIN
8
0
0.58
0.30
2.79
1.78
B9.65
8.38 A
10.67
9.65
2.79
1.78
0 -8
0.25
GAGE PLANE
4215105/A 11/2017
TO-263 - 4.83 mm max height
KTT0003B
TO-263
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. Features may not exist and shape may vary per different assembly sites.
4. Reference JEDEC registration TO-263, except minimum lead thickness and minimum exposed pad length.
1
0.25 C A B
3
OPTIONAL
NOTE 3
NOTE 3
THERMAL PAD
EXPOSED
3
4
1
OPTIONAL LEAD FORM
SCALE 1.000
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EXAMPLE BOARD LAYOUT
0.07 MAX
ALL AROUND
0.07 MIN
ALL AROUND
(6.9)
(10.5)
3X (4)
3X (1.05)
(4.1)(6.55)
(2.54)
(R0.05) TYP
4215105/A 11/2017
EXPOSED METAL SHOWN
TO-263 - 4.83 mm max height
KTT0003B
TO-263
LAND PATTERN EXAMPLE
SCALE:5X
SYMM
PKG
1
3
4
NOTES: (continued)
5. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature numbers
SLMA002(www.ti.com/lit/slm002) and SLMA004 (www.ti.com/lit/slma004).
6. Vias are optional depending on application, refer to device data sheet. It is recommended that vias under paste be filled, plugged or tented.
OPENING
SOLDER MASK METAL
NON SOLDER MASK
DEFINED
SOLDER MASK DETAILS
EXPOSED
METAL
SOLDER MASK
OPENING
SOLDER MASK
METAL UNDER
SOLDER MASK
DEFINED
EXPOSED
METAL
23
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EXAMPLE STENCIL DESIGN
40X (1.07)
40X (1.03)
(1.27 TYP)
(1.23 TYP)
(1.56) TYP
(6.55)
(2.54)
3X (4)
3X (1.05)
(R0.05) TYP
(0.615) TYP
4215105/A 11/2017
NOTES: (continued)
TO-263 - 4.83 mm max height
KTT0003B
TO-263
7. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
8. Board assembly site may have different recommendations for stencil design.
1
3
4
BASED ON 0.125 mm THICK STENCIL
SOLDER PASTE EXAMPLE
EXPOSED PAD
60% PRINTED SOLDER COVERAGE BY AREA
SCALE:6X
SYMM
PKG
EXPOSED METAL
TYP
24
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TAPE AND REEL INFORMATION
*All dimensions are nominal
Device Package
Type Package
Drawing Pins SPQ Reel
Diameter
(mm)
Reel
Width
W1 (mm)
A0
(mm) B0
(mm) K0
(mm) P1
(mm) W
(mm) Pin1
Quadrant
LM1086CSX-2.5/NOPB DDPAK/
TO-263 KTT 3 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2
LM1086CSX-3.3/NOPB DDPAK/
TO-263 KTT 3 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2
LM1086CSX-ADJ/NOPB DDPAK/
TO-263 KTT 3 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2
LM1086ILD-3.3/NOPB WSON NGN 8 1000 178.0 12.4 4.3 4.3 1.3 8.0 12.0 Q1
LM1086ISX-1.8/NOPB DDPAK/
TO-263 KTT 3 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2
LM1086ISX-3.3/NOPB DDPAK/
TO-263 KTT 3 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2
LM1086ISX-5.0/NOPB DDPAK/
TO-263 KTT 3 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2
LM1086ISX-ADJ/NOPB DDPAK/
TO-263 KTT 3 500 330.0 24.4 10.75 14.85 5.0 16.0 24.0 Q2
PACKAGE MATERIALS INFORMATION
www.ti.com 20-Sep-2016
Pack Materials-Page 1
*All dimensions are nominal
Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
LM1086CSX-2.5/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0
LM1086CSX-3.3/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0
LM1086CSX-ADJ/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0
LM1086ILD-3.3/NOPB WSON NGN 8 1000 210.0 185.0 35.0
LM1086ISX-1.8/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0
LM1086ISX-3.3/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0
LM1086ISX-5.0/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0
LM1086ISX-ADJ/NOPB DDPAK/TO-263 KTT 3 500 367.0 367.0 45.0
PACKAGE MATERIALS INFORMATION
www.ti.com 20-Sep-2016
Pack Materials-Page 2
MECHANICAL DATA
NDE0003B
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PACKAGE OUTLINE
C
8X 0.35
0.25
2X
2.4
0.8 MAX
(0.25)
(0.25) (0.2)
(0.15)
0.05
0.00
8X 0.6
0.4
3 0.05
2.2 0.05
6X 0.8
A4.1
3.9 B
4.1
3.9
(0.2) TYP
WSON - 0.8 mm max heightNGN0008A
PLASTIC SMALL OUTLINE - NO LEAD
4214794/A 11/2019
PIN 1 INDEX AREA
SEATING PLANE
0.08 C
1
45
8
PIN 1 ID 0.1 C A B
0.05 C
THERMAL PAD
EXPOSED SYMM
SYMM
9
DETAIL A
SEE
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. The package thermal pad must be soldered to the printed circuit board for thermal and mechanical performance.
SCALE 3.000
PIN 1 ID DETAIL A
PIN 1 ID
www.ti.com
EXAMPLE BOARD LAYOUT
0.07 MIN
ALL AROUND
0.07 MAX
ALL AROUND
8X (0.3)
(3)
(3.3)
6X (0.8)
(2.2)
( 0.2) VIA
TYP (0.85)
(1.25)
8X (0.5)
(R0.05) TYP
WSON - 0.8 mm max heightNGN0008A
PLASTIC SMALL OUTLINE - NO LEAD
4214794/A 11/2019
SYMM
1
45
8
LAND PATTERN EXAMPLE
EXPOSED METAL SHOWN
SCALE:15X
SYMM 9
NOTES: (continued)
4. This package is designed to be soldered to a thermal pad on the board. For more information, see Texas Instruments literature
number SLUA271 (www.ti.com/lit/slua271).
5. Vias are optional depending on application, refer to device data sheet. If any vias are implemented, refer to their locations shown
on this view. It is recommended that vias under paste be filled, plugged or tented.
SOLDER MASK
OPENING
SOLDER MASK
METAL UNDER
SOLDER MASK
DEFINED
EXPOSED
METAL
METAL
SOLDER MASK
OPENING
SOLDER MASK DETAILS
NON SOLDER MASK
DEFINED
(PREFERRED)
EXPOSED
METAL
www.ti.com
EXAMPLE STENCIL DESIGN
(R0.05) TYP
0.59
4X (1.31)
8X (0.3)
8X (0.5)
4X (0.98)
(3.3)
(0.755)
6X (0.8)
WSON - 0.8 mm max heightNGN0008A
PLASTIC SMALL OUTLINE - NO LEAD
4214794/A 11/2019
NOTES: (continued)
6. Laser cutting apertures with trapezoidal walls and rounded corners may offer better paste release. IPC-7525 may have alternate
design recommendations.
SOLDER PASTE EXAMPLE
BASED ON 0.125 mm THICK STENCIL
EXPOSED PAD 9:
78% PRINTED SOLDER COVERAGE BY AREA UNDER PACKAGE
SCALE:20X
SYMM
1
45
8
METAL
TYP
SYMM 9
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