ETA4054

www.etasolution.com

4

Powering Minds of the Smart

PIN DESCRIPTION

SOT23-5

PIN #

NAME DESCRIPTION

1

STAT Open-Drain Charge Status Output. The STAT pin outputs low when the battery is charging.

Upon the completion of the charge cycle, it becomes high-impendence.

2

GND

Ground.

3

BAT

Charge Current Output. This pin provides charge current to the battery and regulates the

final float voltage to 4.2V which is set by an internal precision resistor divider.

4

VIN

Positive Input Supply. Needs to be bypassed with at least a 1μF capacitor.

5

ISET

Program, Monitor the charge current and Shutdown. This pin set to 1V in constant-current

mode. The charge current is programmed by connecting a 1% resistor (Rset), between

ISET, to GND pin. The charge current can be calculated using the following formula:

IBAT=

1

Rset

×1000-(

1

3.6 ×

1

Rset

×1000)

2

The ISET pin can also be used to switch the charger to shutdown mode by disconnecting

the program resistor from ground.

FUNCTIONAL DESCRIPTIONS

The ETA4054 is a single cell, fully integrated constant current (CC)/constant voltage (CV) Li-ion battery charger. It can

deliver up to 1A of charge current with a final float voltage accuracy of 1%. The ETA4054 has a build-in thermal

regulation circuitry that ensures its safe operation. No blocking diode or external current sense resistor is required;

hence reduce the external components for a basic charger circuit to two. The ETA4054 is also capable of operating

from a USB power source.

Normal Charge Cycle

The ETA4054 initiates a charge cycle once the voltage at the VIN pin rises above the UVLO threshold level. A 1%

precision resistor needs to be connected from the ISET pin to ground. If the voltage at the BAT pin is less than 2.9V,

the charger enters trickle charge mode. In this mode, the charge current is reduced to nearly 1/10 the programmed

value until the battery voltage is raised to a safe level for full current charging.

The charger switches to constant-current mode as the BAT pin voltage rises above 2.9V, the charge current is thus

resumed to full programmed value. When the final float voltage (4.2V) is reached, the ETA4054 enters constant-voltage

mode and the charge current begins to decrease until it drops to 1/10 of the preset value and ends the charge cycle.

Programming Charge Current

The charge current is programmable by setting the value of a precision resistor connected from the ISET pin to ground.