6

CHRG (Pin 1): Open-Drain Charge Status Output. When

the battery is charging, the CHRG pin is pulled low by an

internal N-channel MOSFET. When the charge cycle is

completed, a weak pull-down of approximately 20

µA is

connected to the CHRG pin, indicating an “AC present”

condition. When the KB4540 detects an undervoltage

lockout condition, CHRG is forced high impedance.

GND (Pin 2): Ground.

BAT (Pin 3): Charge Current Output. Provides charge

current to the battery and regulates the final float voltage

to 4.2V. An internal precision resistor divider from this pin

sets the float voltage which is disconnected in shutdown

mode.

and should be bypassed with at least a 1

µF capacitor.

than 2

µA.

PROG (Pin 5): Charge Current Program, Charge Current

Monitor and Shutdown Pin. The charge current is pro-

When charging in constant-current mode, this pin servos

to 1V. In all modes, the voltage on this pin can be used to

measure the charge current using the following formula:

The PROG pin can also be used to shut down the charger.

Disconnecting the program resistor from ground allows

a 3

µA current to pull the PROG pin high. When it reaches

the 1.21V shutdown threshold voltage, the charger enters

shutdown mode, charging stops and the input supply

current drops to 25

µA. This pin is also clamped to

approximately 2.4V. Driving this pin to voltages beyond

the clamp voltage will draw currents as high as 1.5mA.

normal operation.

KB4540

Kingbor Technology Co.,Ltd

TEL:(86)0755-26508846 FAX:(86)0755-26509052

PIN FUNCTIONS