LTC4126-ADJ

1

Rev. 0

For more information www.analog.com

TYPICAL APPLICATION

FEATURES

DESCRIPTION

Wireless Li-Ion Charger with

1.2V Step-Down DC/DC Converter

The LTC®4126-ADJ is a low-power wireless single-cell

Li-Ion battery charger with an integrated step-down DC/

DC regulator. The step-down regulator is a low-noise multi-

mode charge pump which is powered from the battery and

provides a regulated 1.2V at the output. The switching

frequency is set to either 50kHz or 75kHz depending on the

mode to keep any switching noise out of the audible range.

The constant-current constant-voltage Li-Ion battery

charger has automatic recharge, automatic termination

by safety timer, and battery temperature monitoring via

an NTC pin. Charge current is programmable from 1mA

to 50mA via an external resistor. Undervoltage protection

disconnects the battery from all loads when the battery

voltage is below 3.0V.

The small package and minimal external component count

make the LTC4126-ADJ and its variants suitable for hear-

ing aid applications and other low power portable devices.

See the chart below.

Top and Bottom View of the IC with

Complete Application Circuit

APPLICATIONS

n

Wireless Li-Ion Battery Charger Plus High

Efficiency Multi-Mode Charge Pump DC/DC

n

Programmable Charge Current from 1mA to 50mA

Via an External Resistor

n

Wideband Rx Frequency: DC to >10MHz

n

Integrated Rectifier with Overvoltage Limit

n

Charge Voltage: 4.2V

n

Low Battery Disconnect: 3.0V

n

NTC Pin for Temperature Qualified Charging

n

DC/DC Regulated Output: 1.2V

n

DC/DC Output Current: Up to 60mA

n

50kHz/75kHz Switching, No Audible Noise

n

Pushbutton and/or Digital on/off Control for DC/DC

n

Thermally Enhanced 12-Lead 2mm × 2mm LQFN

Package

n

Hearing Aids

n

Low Power Li-Ion Powered Devices

n

Wireless Headsets

n

IoT Wearables

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8µH

68nF

12.4k

2.2µF

1.2V

TRANSMITTER

AIR GAP

ACIN

OUT

PROG

GND

Li-Ion

4.2V

4126-ADJ TA01

LTC4126-ADJ

BAT

NTC

CHRG

+–

+

ACPR

STAT2

DIGITAL I/O

STAT1

EN

TO BAT

Document Feedback

PARAMETER

LTC4126-ADJ

LTC4126-10

LTC4126

Charge Current

Programmable

10mA

7.5mA

Charge Timer

6 Hours

3 Hours

6 Hours

Charge Voltage

4.2V

4.1V/4.2V

4.2V/4.35V

EN Pin Polarity

Active High

Active Low

Active High

EN Pin Pull-Up

N/A

1MΩ

N/A

3.2V

3.5V

3.2V

DC/DC

Mode 3

Threshold

1.1V

1.05V

1.1V

Timing

110ms

1.7s

110ms