LTC1732-8.4 Ver la hoja de datos (PDF) - Linear Technology

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LTC1732-8.4

Lithium-Ion Linear Battery Charger Controller

Linear Technology 

LTC1732-8.4

PIN FUNCTIONS

BAT (Pin 1): Battery Sense Input. A bypass capacitor of

10µF or more is required to keep the loop stable when the

battery is not connected. A precision internal resistor

divider sets the final float voltage. The resistor divider is

disconnected in sleep mode to reduce the current drain on

the battery.

SEL (Pin 2): This pin must be connected to VCC.

CHRG (Pin 3): Open-Drain Charge Status Output. When

the battery is charging, the CHRG pin is pulled low by an

internal N-channel MOSFET. When the charge current

drops to 10% of the full-scale current for more than 15ms,

the N-channel MOSFET turns off and a 35µA current

source is connected from the CHRG pin to GND. When the

timer runs out or the input supply is removed, the current

source is disconnected and the CHRG pin is forced into a

high impedance state.

TIMER (Pin 4): Timer Capacitor and Constant-Voltage

Mode Disable Input Pin. The timer period is set by placing

a capacitor, CTIMER, to GND. The timer period is tTIMER =

(CTIMER • 3 hours)/(0.1µF). When the TIMER pin is

connected to VCC, the timer is disabled, thus the constant-

voltage mode is turned off and the IC will operate in

constant-current mode only. Shorting the TIMER pin to

GND will disable the internal timer function and the C/10

function.

GND (Pin 5): Ground.

PROG (Pin 6): Charge Current Program and Shutdown

Input Pin. The charge current is programmed by connect-

ing a resistor, RPROG to ground. The charge current is IBAT

= (VPROG • 800Ω)/(RPROG • RSENSE). The IC can be forced

into shutdown by floating the PROG pin and allowing the

internal 2.5µA current source to pull the pin above the

2.457V shutdown threshold voltage.

DRV (Pin 7): Drive Output Pin for the P-Channel MOSFET

or PNP Transistor. If a PNP transistor is used, it must have

high gain (see Applications Information section).

VCC (Pin 8): Input Supply Voltage. VCC can range from

8.8V to 12V. If VCC drops below VBAT + 54mV, for example

when the input supply is disconnected, then the IC enters

sleep mode with ICC < 30µA. Bypass this pin with a 1µF

capacitor.

SENSE (Pin 9): Current Sense Input. A sense resistor,

RSENSE, must be connected from VCC to the SENSE pin.

This resistor is chosen using the following equation:

RSENSE = (VPROG • 800Ω)/(RPROG • IBAT)

ACPR (Pin 10): Wall Adapter Present Output. When the

input voltage (wall adapter) is applied to the LTC1732-8.4,

this pin is pulled to ground by an internal N-channel

MOSFET which is capable of sinking 5mA to drive an

external LED (See Applications Information Section).

17328f

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