LTC4121 Datasheet | Linear Technology

LTC4121/LTC4121-4.2 40V 400m A Synchronous Step-Down Battery Charger Features nn Wide Input Voltage Range: 4.4V to 40V nn Temperature pensated Input Voltage Regulation for Maximum Power Point Tracking (MPPT) nn Adjustable Float Voltage 3.5V to 18V (LTC4121) nn Fixed 4.2V Float Voltage Option (LTC4121-4.2) nn High Efficiency: Up to 95% nn 50m A to 400m A Programmable Charge Current nn ±1% Feedback Voltage Accuracy nn Programmable 5% Accurate Charge Current nn Thermally Enhanced, Low Profile (0.75mm) 16-Lead (3mm × 3mm) QFN Package APPLICATIONS nn Handheld Instruments nn Solar Powered Devices nn Industrial/Military Sensors and Devices L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. DESCRIPTION The LTC®4121 is a 400m A constant-current/constantvoltage (CC/CV) synchronous step-down battery charger. In addition to CC/CV operation, the LTC4121 regulates its input voltage to a programmable percentage of the input open-circuit voltage. This technique maintains maximum power transfer with high impedance input sources such as solar panels. An external resistor programs the charge current up to 400m A. The LTC4121-4.2 is suitable for charging Li-Ion/ Polymer batteries, while the programmable float voltage of the LTC4121 is suitable for several battery chemistries. The LTC4121 and LTC4121-4.2 include an accurate RUN pin threshold, low voltage battery preconditioning and bad battery fault detection, timer termination, auto-recharge, and NTC temperature qualified charging. The FAULT pin provides an indication of bad battery or temperature faults. Once charging is terminated, the LTC4121 signals end-ofcharge via the CHRG pin, and enters a low current SLEEP mode. An auto-restart feature starts a new charging cycle if the battery voltage drops by 2.2%. TYPICAL APPLICATION High Efficiency, Wide Input Voltage Range Charging with...