ADVANCE INFORMATION Alt information in this data sheet is preliminary and subject to change. 8/95 MAKI 1 to 3-Cell, High-Power, Low-Noise, Step-Up DC-DC Converters General Description The MAX848/MAX849 boost converters set a new stan- dard of high efficiency and high integration for noise- sensitive power-supply applications, such as portable phones and small systems with RF data links. The heart of these devices is a synchronous boost-topology regu- jator that generates a fixed 3.3V output (or 2.7V to 5V adjustable output) from one to three NiCd/NiMH cells or one lithium-ion cell. Synchronous rectification provides a 5% efficiency improvement over similar non-synchronous boost regu- lators. In standby mode, pulse-skipping PFM operation keeps the output voltage alive with only 150uW quies- cent power consumption. Fixed-frequency PWM opera- tion ensures that the switching noise spectrum is confined to the 300kHz fundamental and its harmonics, allowing easy post-filtering noise reduction. Synchronizing to a 200kHz to 400kHz external clock will achieve even tighter noise-spectrum control. Battery monitoring is provided by a 2-channel voltage-to- frequency type A/D converter. One channel is internally connected to the battery input, while the other channel is brought out for monitoring external voltages (AIN pin). A latch is included for push-on/push-off contro! via a momentary pushbutton switch; otherwise, start-up can be automatic with battery installation. Upon power-up, an internal comparator monitors the output voltage to gener- ate a power-good output (PWROK). These two devices are identical, except for their low- side, N-channel MOSFET power switches: 0.5A for the MAX848, 1A for the MAX849. Applications Digital Cordless Phones PCS Phones Hand-Held Instruments Palmtop Computers Personal Communicators Local 3.3V to 5V Supplies MAXIMA Features # 90% Efficiency from 1.1V Input Guaranteed 200mA Output from 1.1V Input (MAX849), (100mA for MAX848) Regulated 3.3V or Adjustable Output (2.7V to 5V) 0.8V to 5V Input Range Low-Power (0.15mW) Standby Mode Low-Noise Constant-Frequency Mode (300kHz) e-?---t t+ @ > Synchronizable Switching Frequency (200kHz to 400kHz) 2-Channel A/D Converter with Serial Output @ Power-Good Function = : 2 : S @ Integrated On/Off Functions Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX848CSE OC to +70C 16 Narrow SO MAX848C/D OC to +70C Dice* MAX848ESE -40C to +85C 16 Narrow SO MAX849CSE OC to +70C 16 Narrow SO MAX849C/D OC to +70C Dice* MAX849ESE -40C to +85C 16 Narrow SO "Contact factory for dice specifications. Typical Operating Circuit 70 MICROCONTROLLER A0 CHANNEL 2 ___ MAMIM SHDN =MAX849 VIN PWROK ON + 1+ CLK/SEL DATA aout | _[BATTERY INTAD SENSE ~ 3.aV vout AT 200A + x (marae FB PGND pS RSTIN REF = ND = L Maxim Integrated Products 4-173 Call toll free 1-800-998-8800 for free samples or literature.MAX848/MAX849 1 to 3-Cell, High-Power, Low-Noise, Step-Up DC-DC Converters Pin Configuration TOP VIEW on [7] 16] vIN an [2 | 5] SHON REF [3] an axim [is YOU" GND MAX848 4ay LX SENSE 4 MAXBAS 8 PGND RSTIN [6 | [13] CLHVSEL F3 [7] io} oATA PwroK [i a} iNTAD so 4-174 MAAXIMA