Datasheet

bq24030, bq24031
bq24032A, bq24035, bq24038
SLUS618H –AUGUST 2004–REVISED OCTOBER 2009............................................................................................................................................... www.ti.com
If the output drops below ~1 V, an output short-circuit condition is declared and the input FETs (AC and USB) are
turned off. To recover from this state, a 500-Ω pullup resistor from each input is applied (switched) to the output.
To recover, the load on the output has to be reduced {Rload > 1 V × 500 Ω/ (Vin–Vout)} such that the pullup
resistor is able to lift the output voltage above 1 V, for the input FETs to be turned back on.
If the output drops 200 mV below the battery voltage, the battery FET is considered in short circuit and the
battery FET turns off. To recover from this state, there is a 10-mA ±8 mA current source from the battery to the
output. Once the output load is reduced, such that the current source can pick up the output within 200 mV of the
battery, the FET turns back on (As Vout increases in voltage the current source's drive drops toward 2 mA).
If the short is removed, and the minimum system load is still too large [R<(VBat –200 mV / 2mA)], the
short-circuit protection can be temporarily defeated. The battery short-circuit protection can be disabled
(recommended only for a short time) if the voltage on the DPPM pin is less than 1 V. Pulsing this pin below 1 V,
for a few microseconds, should be enough to recover.
This short-circuit disable feature was implemented mainly for power up when inserting a battery. Because the
BAT input voltage rises much faster than the OUT voltage (Vout<Vbat-200 mV), with most any capacitive load on
the output, the part can get stuck in short-circuit mode. Placing a capacitor between the DPPM pin and ground
slows the V
DPPM
rise time, during power up, and delays the short-circuit protection. Too large a capacitance on
this pin (too much of a delay) could allow too-high currents if the output was shorted to ground. The
recommended capacitance is 1 nF to 10 nF. The V
DPPM
rise time is a function of the 100-µA DPPM current
source, the DPPM resistor, and the capacitor added.
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Product Folder Link(s): bq24030, bq24031 bq24032A, bq24035, bq24038