LTC4121-4.2 Datasheet

• Wide Input Voltage Range: 4.4V to 40V
• Temperature Compensated Input Voltage Regulation for Maximum Power Point Tracking (MPPT)
• Fixed 4.2V Float Voltage Option
• High Efficiency: Up to 95%
• 50mA to 400mA Programmable Charge Current
• ±1% Feedback Voltage Accuracy
• Programmable 5% Accurate Charge Current
• Thermally Enhanced, Low Profile (0.75mm) 16-Lead (3mm × 3mm) QFN Package

• Handheld Instruments
• Solar Powered Devices
• Industrial/Military Sensors and Devices

The LTC4121 is a 400mA 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 400mA. The LTC4121-4.2 is suitable for charging Li-Ion/ Polymer batteries.

The 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.