MAX1925/MAX1926 19-2556 Rev 1 10/02 Switch-Mode 1-Cell Li+ Chargers General Description Features The MAX1925/MAX1926 single-cell lithium-ion (Li+) Small (4mm 4mm) Package switch-mode battery chargers use an external PMOS 4.25V to 12V Input Range (MAX1926) pass element step-down configuration. Charge current is programmable, and an external capacitor sets the Overvoltage Lockout at 6.1V (MAX1925) maximum charge time. 0.75% Battery Regulation Voltage Additional features include automatic input power Set Charge Current with One Resistor detection (ACON output), logic-controlled enable, and temperature monitoring with an external thermistor. The Automatic Input Power Sense MAX1925 disables charging for inputs greater than 6.1V, while the MAX1926 charges for inputs between LED (or Logic-Out) Charge Status and Fault 4.25V and 12V. Indicator The MAX1925/MAX1926 feature two precondition levels Programmable Safety Timer to restore near-dead cells. The devices source 4mA to Autorestart at Cell = 4V a cell that is below 2V while sourcing C/10 to a cell between 2V and 3V. Full charge current is then applied Thermistor Monitor Input above 3V. A CHG output drives an LED to indicate charging (LED on) and fault conditions (LED blinking). The MAX1925/MAX1926 are available in a 12-pin 4mm 4mm thin QFN package and are specified over Ordering Information the extended temperature range (-40C to +85C). An evaluation kit is available to speed design. INPUT TEMP PIN- PART CHARGING RANGE PACKAGE RANGE Applications 12 Thin QFN MAX1925ETC -40C to +85C 4.5V to 6.1V 4mm x 4mm Digital Cameras 12 Thin QFN Self-Charging Battery Packs MAX1926ETC -40C to +85C 4.25V to 12V 4mm x 4mm PDAs Cradle Chargers Typical Operating Circuit INPUT Pin Configuration 4.5V TO 12V IN INP EXT IN INP EXT PGND 12 11 10 CS CHG 1 9 PGND LED BATT CHG MAX1925 EN 2 8 GND MAX1925 CT MAX1926 GND MAX1926 THRM 3 7 BATT THRM ON EN OFF ACON 1-CELL 45 6 Li+ BATTERY ACON CT CS THIN QFN Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct at 1-888-629-4642, or visit Maxims website at www.maxim-ic.com. EVALUATION KIT AVAILABLESwitch-Mode 1-Cell Li+ Chargers ABSOLUTE MAXIMUM RATINGS IN, INP, ACON to GND...........................................-0.3V to +14V Continuous Power Dissipation (T = +70C) A Exposed Paddle Soldered to Board CHG, EXT to PGND ...................................-0.3V to (V + 0.3V) INP (derate 16.9mW/C above +70C).............................1349mW CS, BATT, EN, THRM to GND ..................................-0.3V to +6V Exposed Paddle Unsoldered CT to GND................................................................-0.3V to +4V (derate 9mW/C above +70C)....................................721mW EN, THRM, CT to IN................................................-14V to +0.3V Operating Temperature Range ...........................-40C to +85C INP to IN ................................................................-0.3V to +0.3V Junction Temperature......................................................+150C PGND to GND .......................................................-0.3V to +0.3V Storage Temperature Range .............................-65C to +150C CS to BATT............................................................-0.3V to +0.3V Lead Temperature (soldering, 10s) .................................+300C EXT Continuous RMS Current.........................................100mA Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (V = V = 0, V = V = V = 5V, V = V = V = 4V, THRM = 10k to GND, C = 100nF, T = 0C to +85C, PGND GND INP IN CHG BATT CS EN CT A unless otherwise noted. Typical values are at T = +25C.) A PARAMETER CONDITIONS MIN TYP MAX UNITS Supply Voltage Range V , V (MAX1925 does not charge above 6.1V) 4.5 12.0 V INP IN MAX1925 4.30 4.50 4.78 V , V rising INP IN MAX1926 4.00 4.25 4.50 ACON Trip Point V MAX1925 4.17 4.30 4.43 V , V falling INP IN MAX1926 3.90 4.15 4.40 Rising 5.8 6.4 INP, IN Shutdown Threshold MAX1925 V Falling 5.3 5.9 EN Input Resistance MAX1926 internally pulled up to 3V 125 300 550 k EN Leakage Current MAX1925 -1 +1 A EN Logic Input High Threshold 2 V EN Logic Input Low Threshold 0.8 V DONE state, V = 4.1V 25 50 BATT BATT + CS Input Current EN = GND (Note 1) 2 10 A (Total Current into BATT and CS) V = V = V = 4V, shutdown (Note 1) 2 10 BATT INP IN CS Input Current Charging 39 A EN = GND 5 8 mA V = V = V = 4V, shutdown 2 10 A BATT INP IN IN + INP Total Input Current V = 4.1V charging 10 BATT mA V = 4.3V done 5 8 BATT VOLTAGE LOOP Voltage Loop Set Point 4.1685 4.2000 4.2315 V Voltage Loop Hysteresis 15 mV BATT Prequal1 Voltage Threshold 1.9 2 2.1 V BATT Prequal2 Voltage Threshold 2.85 3 3.15 V 2 MAX1925/MAX1926