ltc4054x-4.2 Linear Technology Corporation, ltc4054x-4.2 Datasheet - Page 6

• Manufacturer Part Number: ltc4054x-4.2
• Description: Standalone Linear Li-ion Battery Charger With Thermal Regulation In Thinsot
• Manufacturer: Linear Technology Corporation

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 A is
connected to the CHRG pin, indicating an “AC present”
condition. When the LTC4054 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.
V
power to the charger. V
and should be bypassed with at least a 1 F capacitor.
When V
LTC4054 enters shutdown mode, dropping I
than 2 A.
LTC4054-4.2/LTC4054X-4.2
PI FU CTIO S
6
CC
U
(Pin 4): Positive Input Supply Voltage. Provides
CC
drops to within 30mV of the BAT pin voltage, the
U
U
CC
can range from 4.25V to 6.5V
BAT
to less
PROG (Pin 5): Charge Current Program, Charge Current
Monitor and Shutdown Pin. The charge current is pro-
grammed by connecting a 1% resistor, R
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 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 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
normal operation.
I
BAT
= (V
PROG
PROG
/R
PROG
to ground will return the charger to
) • 1000
PROG
, to ground.
405442xf