LTC4059/LTC4059A
5
4059fb
PI FU CTIO S
UUU
GND (Pins 1, 7): Ground/Exposed Pad. The exposed
package pad is ground and must be soldered to the PC
board for maximum heat transfer.
Li CC (Pin 2, LTC4059): Li-Ion/Constant Current Input
Pin. Pulling this pin above V
Li CC
disables voltage mode
thereby providing a constant current to the BAT pin. This
feature is useful for charging Nickel chemistry batteries.
Tie to GND if unused.
ACPR (Pin 2, LTC4059A): Open-Drain Power Supply
Status Output. When V
CC
is greater than the undervoltage
lockout threshold, the ACPR pin will pull to ground;
otherwise the pin is forced to a high impedance state.
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 this float voltage and is disconnected in shutdown
mode.
V
CC
(Pin 4): Positive Input Supply Voltage. This pin
provides power to the charger. V
CC
can range from 3.75V
to 8V. This pin should be bypassed with at least a 1µF
capacitor. When V
CC
is within 35mV of the BAT pin
voltage, the LTC4059 enters shutdown mode, dropping
I
BAT
to less than 4µA.
PROG (Pin 5): Charge Current Program and Charge Cur-
rent Monitor Pin. Connecting a resistor, R
PROG
, to ground
programs the charge current. When charging in constant-
current mode, this pin servos to 1.21V. In all modes, the
voltage on this pin can be used to measure the charge
current using the following formula:
I
V
R
BAT
PROG
PROG
= • 1000
EN (Pin 6): Enable Input Pin. Pulling this pin above the
manual shutdown threshold (V
MS
is typically 0.92V) puts
the LTC4059 in shutdown mode, thus terminating a charge
cycle. In shutdown mode, the LTC4059 has less than 25µA
supply current and less than 1µA battery drain current.
Enable is the default state, but the pin should be tied to
GND if unused.
