LTC4121LTC4121-4.2 Series

40V 400mA Synchronous Step-Down Battery Charger

Catalog

40V 400mA Synchronous Step-Down Battery Charger

Part	Voltage - Supply (Max) [Max]	Package / Case	Battery Chemistry	Mounting Type	Current - Charging	Operating Temperature [Min]	Operating Temperature [Max]	Charge Current - Max [Max]	Supplier Device Package	Battery Pack Voltage
Analog Devices LTC4121EUD	40 V	16-WFQFN Exposed Pad	Multi-Chemistry	Surface Mount	Constant - Programmable	-40 °C	125 ¯C	400 mA	16-QFN (3x3)	18 V
Analog Devices LTC4121EUD#PBF	40 V	16-WFQFN Exposed Pad	Multi-Chemistry	Surface Mount	Constant - Programmable	-40 °C	125 ¯C	400 mA	16-QFN (3x3)	18 V
Analog Devices LTC4121IUD#TRPBF	40 V	16-WFQFN Exposed Pad	Multi-Chemistry	Surface Mount	Constant - Programmable	-40 °C	125 ¯C	400 mA	16-QFN (3x3)	18 V
Analog Devices LTC4121EUD#TRPBF	40 V	16-WFQFN Exposed Pad	Multi-Chemistry	Surface Mount	Constant - Programmable	-40 °C	125 ¯C	400 mA	16-QFN (3x3)	18 V

Catalog

40V 400mA Synchronous Step-Down Battery Charger

Key Features

• 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)

• Fixed 4.2V Float Voltage Option (LTC4121-4.2)

• 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

Description

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, 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. TheFAULTpin provides an indication of bad battery or temperature faults.Once charging is terminated, the LTC4121 signals end-ofcharge via theCHRGpin, and enters a low current SLEEP mode. An auto-restart feature starts a new charging cycle if the battery voltage drops by 2.2%.ApplicationsHandheld InstrumentsSolar Powered DevicesIndustrial/Military Sensors and Devices