LTC4121
LTC4121-4.2

RECOMMENDED FOR NEW DESIGNS

40V 400mA Synchronous Step-Down Battery Charger

Part Models: 8
1ku List Price: Starting From $3.14

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Overview

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

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. 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%.

Applications

Handheld Instruments
Solar Powered Devices
Industrial/Military Sensors and Devices

Part Models: 8
1ku List Price: Starting From $3.14

Documentation

ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal. View our quality and reliability program and certifications for more information.

Part Model	Pin/Package Drawing	Documentation	CAD Symbols, Footprints, and 3D Models
LTC4121EUD#PBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4121EUD#TRPBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4121EUD-4.2#PBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4121EUD-4.2#TRPBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4121IUD#PBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4121IUD#TRPBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4121IUD-4.2#PBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys
LTC4121IUD-4.2#TRPBF	16-Lead QFN (3mm x 3mm x 0.75mm w/ EP)	Material Declaration Reliablity Data Package Resources	Ultra Librarian SamacSys

This is the most up-to-date revision of the Data Sheet.

Software Resources

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Hardware Ecosystem

Parts	Product Life Cycle	Description
Protection Switches & Controllers 2
LTC4417	RECOMMENDED FOR NEW DESIGNS	Prioritized PowerPath^™ Controller
LTC4359	RECOMMENDED FOR NEW DESIGNS	Ideal Diode Controller with Reverse Input Protection

Evaluation Kits

LTC4121EUD Demo Board | 400mA Synchronous Buck Battery Charger, VIN = 4.4V to 40V, VBAT = Adjustable

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Product Details

Demonstration circuit 1977A is the demonstration board for LTC4121EUD-4.2/LTC4121EUD, a 400mA Synchronous Buck Battery Charger. The DC1977A supports the Maximum Power Point Tracking (MPPT) feature on the LTC4121EUD, for use with Photovoltaic (PV) cells or highly resistive sources.