STBC21 datasheet(22/54 Pages) STMICROELECTRONICS

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Detailed description

STBC21

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Doc ID 023256 Rev 1

Equation 2

which is not compatible with the thermal specifications of the package used. In this situation

either the charging current must be reduced (increasing the charging time) or the STBC21

enters into thermal shutdown.

This effect can be seen even in pre-charge but is less critical because this phase generally

last few minutes and the current is lower but can become longer in case the chip goes into

thermal shutdown.

To allow a higher current capability during charging, the power dissipation must be reduced

acting on the voltage drop between input and output. To keep this difference at a minimum

value the STBC21 provides a pin to drive a controller downstream so that the input voltage

depends on the battery voltage.

The input voltage waveform is shaped as reported in

Figure 12.

Charging process diagram

During pre-charge, until VBAT reaches 2.8 V (VBAT_QP threshold), the input voltage must be

regulated at VCC_QP. When VBAT goes over 2.8 V, VCC starts to increase, keeping a constant

voltage difference with VBAT (IODROP_QP).

5.7

Alarms

The STBC21 implements four kinds of alarms: battery alarm, charger alarm, ASD

(automatic shutdown) alarm and device temperature alarm.

)

(

BAT

OUT

−

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