BL4054/BL4054B
800mA Standalone Linear Li-Ion Battery Charger
with Thermal Regulation in SOT23-5/TSOT23-5
Pin Description
PIN
NAME
FUNCTION
Open-Drain Charge Status Output. When the battery is
charging, the CHRGb pin is pulled low by an internal
N-channel MOSFET. When the charge cycle is
completed, a weak pull-down of approximately 12
µ
A is
connected to the CHRGb pin, indicating an “AC present”
condition. When the BL4054/BL4054B detects an
under-voltage lockout condition, CHRGb is forced high
impedance.
Ground
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.
Positive Input Supply Voltage. Provides power to the
charger. V
CC
can range from 4.25V to 6.5V and should be
bypassed with at least a 1
µ
F capacitor. When V
CC
drops
to within 30mV of the BAT pin voltage, the
BL4054/BL4054B enters shutdown mode, dropping I
BAT
to
less than 2
µ
A.
Charge Current Program, Charge Current Monitor and
Shutdown Pin. The charge current is Programmed by
connecting a 1% resistor, R
PROG
, from this pin to ground.
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:
I
BAT
= (V
PROG
/ R
PROG
) • 1000
The PROG pin can also be used to shut down the
charger. Disconnecting the Program resistor from ground
allows a 3
µ
A 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
µ
A. 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. Reconnecting R
PROG
to ground will return
the charger to normal operation.
1
CHRGb
2
3
GND
BAT
4
V
CC
5
PROG
PPMIC BU
BL4054/BL4054B Rev 1.4
5/2009
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