Datasheet

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APPLICATION INFORMATION

FUNCTIONAL DESCRIPTION

TEMPERATURE QUALIFICATION (bq24200 and bq24202 only)

bq24200, bq24201

bq24202, bq24203

bq24204, bq24205

SLUS501C – OCTOBER 2001 – REVISED MARCH 2008

Figure 5. Low Dropout Single-Cell Li-Ion/Li-Pol Charger

The bq2420x supports a precision Li-Ion or Li-Pol charging system suitable for single-cells with either coke or

graphite anodes. Figure 5 shows an application schematic and Figure 6 shows the typical charge profile.

The bq24200 and bq24201 continuously monitors battery temperature by measuring the voltage between the TS

and VSS pins. A negative- or a positive-temperature coefficient thermistor (NTC, PTC) and an external voltage

divider typically develop this voltage (see Figure 5 ). The bq24200 and bq24201 compare this voltage against the

internal V

(TS1)

and V

(TS2)

thresholds to determine if charging is allowed (see Figure 7 ). The temperature sensing

circuit is immune to any fluctuation in Vcc since both the external voltage divider and the internal thresholds are

referenced to Vcc.

Once a temperature outside the V

(TS1)

and V

(TS2)

thresholds is detected the bq24200 and bq24201 immediately

suspend the charge. The bq24200 and bq24201 suspend the charge by turning off the power FET and holding

the timer value (i.e., timers are NOT reset). Charge is resumed when the temperature returns to the normal

range.

Product Folder Link(s): bq24200, bq24201 bq24202, bq24203 bq24204, bq24205