LTC4121/LTC4121-4.2 40V 400mA Synchronous Step-Down Battery Charger FEATURESDESCRIPTION n Wide Input Voltage Range: 4.4V to 40V The LTC®4121 is a 400mA constant-current/constant- n Temperature Compensated Input Voltage voltage (CC/CV) synchronous step-down battery charger. Regulation for Maximum Power Point Tracking In addition to CC/CV operation, the LTC4121 regulates its (MPPT) input voltage to a programmable percentage of the input n Adjustable Float Voltage 3.5V to 18V (LTC4121) open-circuit voltage. This technique maintains maximum n Fixed 4.2V Float Voltage Option (LTC4121-4.2) power transfer with high impedance input sources such n High Efficiency: Up to 95% as solar panels. n 50mA to 400mA Programmable Charge Current An external resistor programs the charge current up to n ±1% Feedback Voltage Accuracy 400mA. The LTC4121-4.2 is suitable for charging Li-Ion/ n Programmable 5% Accurate Charge Current Polymer batteries, while the programmable float voltage n Thermally Enhanced, Low Profile (0.75mm) of the LTC4121 is suitable for several battery chemistries. 16-Lead (3mm × 3mm) QFN Package The LTC4121 and LTC4121-4.2 include an accurate RUN pin threshold, low voltage battery preconditioning and bad APPLICATIONS battery fault detection, timer termination, auto-recharge, n and NTC temperature qualified charging. The FAULT pin Handheld Instruments n provides an indication of bad battery or temperature faults. Solar Powered Devices n Industrial/Military Sensors and Devices Once charging is terminated, the LTC4121 signals end-of- L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks charge via the CHRG pin, and enters a low current SLEEP of Linear Technology Corporation. All other trademarks are the property of their respective owners. mode. An auto-restart feature starts a new charging cycle if the battery voltage drops by 2.2%. TYPICAL APPLICATIONHigh Efficiency, Wide Input Voltage Range Charging with LTC4121LTC4121 Efficiency vs VIN at VFLOAT = 8.4V IN INTV 97 CC 200mA, RPROG = 6.04k RUN BOOST 2.2µF 400mA, R 10µF PROG = 3.01k 10k 22nF 95 MPPT SLF6025T-470MR48 LTC4121 SW CHGSNS 93 VIN + V – BAT + 200mV BAT TO 40V 1.96M 91 PROG FB 22µF EFFICIENCY (%) 787k + 89 FREQ GND FBG RPROG Li-Ion VBAT = 8.3V 87 4121 TA01a 5 10 15 20 25 30 35 40 VIN (V) 4121 TA01b 4121fc For more information www.linear.com/LTC4121 1 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Applications Examples Package Description Typical Application Related Parts
