LTC4007 datasheet(5/20 Pages) LINER

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LTC4007

4007i

PI FU CTIO S

DCIN (Pin 1): External DC Power Source Input. Bypass

this pin with at least 0.01

µF. 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

µA pull-up to 3.5V. If

VLOGIC 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

µA.

RT (Pin 4): Timer Resistor. The timer period is set by

placing a resistor, RRT , to GND. This resistor is always

required.

The timer period is tTIMER = (1hour • RRT/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

µA.

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

µA 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

µA 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

µA. If VLOGIC 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

µF to GND provides

loop compensation. Typical full-scale output current is

µA. 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.

ICL (Pin 13): Input Current Limit Indicator. Active low

digital output. Internal 10

µA 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

µA. If VLOGIC 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,

RSENSE, to provide the instantaneous current signals re-

quired for both peak and average current mode operation.

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