BQ24901_13 Datasheet, PDF (9/18 Pages) Texas Instruments – OFFLNE APPLICATIONS

bq24901
APPLICATION INFORMATION
SLUS527 – DECEMBER 2002
Charge Qualification and Pre-Conditioning
The bq24901 starts a charge cycle when power is applied and a battery is present. Charge qualification is based
on battery temperature and voltage. The device suspends charge if the battery temperature is outside the V_LTF
to V_HTF and waits until the battery temperature is within the allowed range. The device also checks the battery
voltage. If the battery voltage is below the low-voltage threshold, V_LOWV, the device use pre-conditioning
current, I_PRECHG, to charge the battery.
Temperature Sense (TS) Input
The bq24901 continuously monitors battery temperature by measuring the voltage between the TS pin and Vss.
A negative temperature coefficient thermistor (NTC) and an external voltage divider typically develop this
voltage. The bq24901 compares this voltage against its internal thresholds to determine if charging is allowed.
To initiate a charge cycle, the battery temperature must be within the V_LTF to V_HTF thresholds. If battery
temperature is outside of this range, the device suspends charge and waits until the battery temperature is within
the V_LTF to V_HTF range. During the charge cycle (both pre-charge and fast charge) the battery temperature must
be within the V_LTF to V_TCO thresholds. If battery temperature is outside of this range, the bq24901 suspends
charge and waits until the battery temperature is within the V_LTF to V_HTF range. The device suspends charge
by turning off the CC pin and holding the timer value (i.e. timers are not reset during a suspend condition).
Figure 4 summarizes this operation.
VCC
VLTF
VHTF
VTCO
VSS
Charge Suspend
Temperature Range
to Initiate Charge
Charge Suspend
Charge Suspend
Temperature Range
During Charge Cycle
Charge Suspend
Figure 4. Temperature Sense Input Thresholds
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