LTC4121 Datasheet

• Wide Input Voltage Range: 4.4V to 40V
• Temperature Compensated Input Voltage Regulation for Maximum Power Point Tracking (MPPT)
• Adjustable Float Voltage 3.5V to 18V (LTC4121)
• 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 programmable float voltage of the LTC4121 is suitable for several battery chemistries.

The LTC4121 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%.