BQ24004 Datasheet, PDF (17/22 Pages) Texas Instruments – TWO-CELL Li-ION CHARGE MANAGEMENT IC FOR PDAs AND INTERNET APPLIANCES

www.ti.com
DETAILED DESCRIPTION
bq24004
bq24005
bq24006
SLUS476B – DECEMBER 2000 – REVISED MAY 2002
POWER FET
The integrated transistor is a P-channel MOSFET. The
power FET features a reverse-blocking Schottky diode,
which prevents current flow from OUT to IN.
An internal thermal-sense circuit shuts off the power FET
when the junction temperature rises to approximately
165°C. Hysteresis is built into the thermal sense circuit.
After the device has cooled approximately 10°C, the
power FET turns back on. The power FET continues to
cycle off and on until the fault is removed.
CURRENT SENSE
The bq2400x regulates current by sensing, on the ISNS
pin, the voltage drop developed across an external sense
resistor. The sense resistor must be placed between the
supply voltage (Vcc) and the input of the IC (IN pins).
VOLTAGE SENSE
To achieve maximum voltage regulation accuracy, the
bq2400x uses the feedback on the VSENSE pin.
Externally, this pin should be connected as close to the
battery cell terminals as possible. For additional safety, a
10-kΩ internal pullup resistor is connected between the
VSENSE and OUT pins.
ENABLE (EN)
The logic EN input is used to enable or disable the IC. A
high-level signal on this pin enables the bq2400x. A
low-level signal disables the IC and places the device in a
low-power standby mode.
17