LTC4002
8
4002f
TYPICAL PERFOR A CE CHARACTERISTICS
UW
T
A
= 25°C, V
CC
= 10V unless otherwise noted.
End-of-Charge Ratio
vs Temperature
TEMPERATURE (°C)
–50
R
EOC
(%)
25
4002 G30
10
–25 0 50
6
7
8
9
14
13
12
11
75 100 125
LTC4002-8.4
End-of-Charge Ratio
vs V
CC
V
CC
(V)
5
R
EOC
(%)
10 15 20 25
4002 G31
10
6
7
8
9
14
13
12
11
LTC4002-8.4
UU
U
PI FU CTIO S
COMP (Pin 1/Pin 1): Compensation, Soft-Start and Shut-
down Control Pin. The COMP pin is the control signal of the
inner loop of the current mode PWM. Charging begins when
the COMP pin reaches 800mV. The recommended compen-
sation components are a 0.47µF (or larger) capacitor and
a 2.2k series resistor. A 100µA current into the compen-
sation capacitor also sets the soft-start slew rate. Pulling
the COMP pin below 360mV will shut down the charger.
V
CC
(Pin 2/Pin 2): Positive Supply Voltage Input. V
CC
can
range from V
BAT(FLT)
+ 0.5V to 22V. A 0.1µF or higher ca-
pacitor is required at the V
CC
pin with the lead length kept
to a minimum. A 10µF low ESR capacitor is also required
at the source pins of the power P-channel MOSFET.
GATE (Pin 3/Pin 3): Gate Drive Output. Driver Output for
the P-Channel MOSFET. The voltage at this pin is internally
clamped to 8V below V
CC
, allowing a low voltage MOSFET
with gate-to-source breakdown voltage of 8V or less to be
used.
PGND, SGND, Exposed Pad, GND (Pins 4, 5, 11/Pin 4):
IC Ground. The exposed pad (DFN) must be soldered to PCB
ground to provide both electrical contact and optimum
thermal performance.
CHRG (Pin 6/Pin 5): Open-Drain Charge Status Output.
When the battery is being charged, the CHRG pin is pulled
low by an internal N-channel MOSFET. When the charge
current drops below the End-of-Charge threshold for more
than 120µs, the N-channel MOSFET turns off and a 25µA
current source is connected from the CHRG pin to GND.
When the timer runs out or the input supply is removed,
the 25µA current source is turned off and the CHRG pin
becomes high impedance.
BAT (Pin 7/Pin 6): Battery Sense Input. A bypass capaci-
tor of 22µF is required to minimize ripple voltage. An
internal resistor divider, which is disconnected in sleep
mode, sets the final float voltage at this pin. If the battery
connection is opened when charging, an overvoltage
circuit will limit the charger output voltage to 10% above
the programmed float voltage.
When V
BAT
is within 250mV of V
CC
, the LTC4002 is forced
into sleep mode, dropping I
CC
to 10µA.
SENSE (Pin 8/Pin 7): Current Amplifier Sense Input. A sense
resistor, R
SENSE
, must be connected between the SENSE
and BAT pins. The maximum charge current is equal to
100mV/R
SENSE
.
NTC (Pin 9/Pin 8): NTC (Negative Temperature Coefficient)
Thermistor Input. With an external 10kΩ NTC thermistor
to ground, this pin senses the temperature of the battery
pack and stops the charger when the temperature is out of
range. When the voltage at this pin drops below 355mV at
(DFN/SO-8)
