
5
LTC4007
4007i
PIU
DCIN (Pin 1):
External DC Power Source Input. Bypass
this pin with at least 0.01
μ
F. See Applications Information.
CHG (Pin 2):
Charge Status Output. When the battery is
being charged, the CHG pin is pulled low by an internal
N-channel MOSFET. Internal 10
μ
A pull-up to 3.5V. If
V
LOGIC
is greater than 3.3V, add an external pull-up. The
timer function can be defeated by forcing this pin below 1V
(or connecting it to GND).
ACP(Pin 3):
Open-Drain output to indicate if the AC
adapter voltage is adequate for charging. This pin is pulled
low by an internal N-channel MOSFET if DCIN is below
BAT. A pull-up resistor is required. The pin is capable of
sinking at least 100
μ
A.
R
T
(Pin 4):
Timer Resistor. The timer period is set by
placing a resistor, R
RT
, to GND. This resistor is always
required.
The timer period is t
TIMER
= (1hour R
RT
/154K).
FAULT (Pin 5):
Active low open-drain output that indi-
cates charger operation has stopped due to a low-battery
conditioning error, or that charger operation is suspended
due to the thermistor exceeding allowed values. A pull-up
resistor is required if this function is used. The pin is
capable of sinking at least 100
μ
A.
GND (Pin 6):
Ground for Low Power Circuitry.
3C4C (Pin 7):
Select 3-cell or 4-cell float voltage by
connecting this pin to GND or open, respectively. Internal
14
μ
A pull-up to 5.3V. This pin can also be driven with
open-collector/drain logic levels. High: 4 cell. Low: 3 cell.
LOBAT (Pin 8):
Low-Battery Indicator. Active low digital
output. Internal 10
μ
A pull-up to 3.5V. If the battery
voltage is below 2.5V/cell (or 2.44V/cell for 4.1V chemis-
try batteries) LOBAT will be low. The pin is capable of
sinking at least 100
μ
A. If V
LOGIC
is greater than 3.3V, add
an external pull-up.
NTC (Pin 9):
A thermistor network is connected from NTC
to GND. This pin determines if the battery temperature is
safe for charging. The charger and timer are suspended
and the FAULT pin is driven low if the thermistor indicates
a temperature that is unsafe for charging. The thermistor
function may be disabled with a 300k to 500k resistor from
DCIN to NTC.
ITH (Pin 10):
Control Signal of the Inner Loop of the
Current Mode PWM. Higher ITH voltage corresponds to
higher charging current in normal operation. A 6k resistor,
in series with a capacitor of at least 0.1
μ
F to GND provides
loop compensation. Typical full-scale output current is
40
μ
A. Nominal voltage range for this pin is 0V to 3V.
PROG (Pin 11):
Current Programming/Monitoring Input/
Output. An external resistor to GND programs the peak
charging current in conjunction with the current sensing
resistor. The voltage at this pin provides a linear indication
of charging current. Peak current is equivalent to 1.19V.
Zero current is approximately 0.3V. A capacitor from
PROG to ground is required to filter higher frequency
components. The maximum resistance to ground is 100k.
Values higher than 100k can cause the charger to shut
down.
NC (Pin 12):
No Connect.
I
CL
(Pin 13):
Input Current Limit Indicator. Active low
digital output. Internal 10
μ
A pull-up to 3.5V. Pulled low if
the charger current is being reduced by the input current
limiting function. The pin is capable of sinking at least
100
μ
A. If V
LOGIC
is greater than 3.3V, add an external
pull-up.
CSP (Pin 14):
Current Amplifier CA1 Input. The CSP and
BAT pins measure the voltage across the sense resistor,
R
SENSE
, to provide the instantaneous current signals re-
quired for both peak and average current mode operation.