LTC4076
7
4076fa
USBIN (Pin 1): USB Input Supply Pin. Provides power to
the battery charger. The maximum supply current is 650mA.
This pin should be bypassed with a 1µF capacitor.
IUSB (Pin 2): Charge Current Program for USB Power.
The charge current is set by connecting a resistor, R
IUSB
,
to ground. When charging in constant-current mode, this
pin servos to 1V. The voltage on this pin can be used to
measure the battery current delivered from the USB input
using the following formula:
I
V
R
HPWR HIGH
I
V
R
BAT
IUSB
IUSB
BAT
IUSB
= =
=
• (
)1000
IIUSB
HPWR LOW• ( )200 =
ITERM (Pin 3): Termination Current Threshold Program.
The termination current threshold, I
TERMINATE
, is set by
connecting a resistor, R
ITERM
, to ground. I
TERMINATE
is set
by the following formula:
I
V
R
TERMINATE
ITERM
=
100
When the battery current, I
BAT
, falls below the termination
threshold, charging stops and the
C
H
R
G output becomes
high impedance.
This pin is internally clamped to approximately 1.5V. Driv-
ing this pin to voltages beyond the clamp voltage should
be avoided.
P
W
R (Pin 4): Open-Drain Power Supply Status Output.
When the DCIN or USBIN pin voltage is sufficient to begin
charging (i.e. when the supply is greater than the under-
voltage lockout threshold and at least 180mV above the
battery terminal), the
P
W
R pin is pulled low by an internal
N-channel MOSFET. Otherwise
P
W
R is high impedance.
This output is capable of sinking up to 10mA, making it
suitable for driving an LED.
C
H
R
G (Pin 5): Open-Drain Charge Status Output. When
the LTC4076 is charging, the
C
H
R
G pin is pulled low by
an internal N-channel MOSFET. When the charge cycle is
completed,
C
H
R
G becomes high impedance. This output
is capable of sinking up to 10mA, making it suitable for
driving an LED.
E
N (Pin 6): Charge Enable Input. A logic low on this pin
enables the charger. If left floating, an internal 2MΩ pull-
down resistor defaults the LTC4076 to charge mode . Pull
this pin high for shutdown.
HPWR (Pin 7): HPWR Enable Input. Used to control the
amount of current drawn from the USB port. A logic high
on the HPWR pin sets the charge current to 100% of the
current programmed by the IUSB pin. A logic low on the
HPWR pin sets the charge current to 20% of the current
programmed by the IUSB pin. An internal 2MΩ pull-down
resistor defaults the HPWR pin to its low current state.
IDC (Pin 8): Charge Current Program for Wall Adapter
Power. The charge current is set by connecting a resis-
tor, R
IDC
, to ground. When charging in constant-current
mode, this pin servos to 1V. The voltage on this pin can
be used to measure the battery current delivered from the
DC input using the following formula:
I
V
R
BAT
IDC
IDC
= •1000
BAT (Pin 9): Charger Output. This pin provides charge
current to the battery and regulates the final float voltage
to 4.2V.
DCIN (Pin 10): Wall Adapter Input Supply Pin. Provides
power to the battery charger. The maximum supply
current is 950mA. This should be bypassed with a 1μF
capacitor.
Exposed Pad (Pin 11): GND. The exposed backside of the
package is ground and must be soldered to PC board ground
for electrical connection and maximum heat transfer.
