STBC21 datasheet(18/54 Pages) STMICROELECTRONICS

18 / 54 page

Detailed description

STBC21

18/54

Doc ID 023256 Rev 1

Figure 6.

Temperature ranges compatible with PSE, power safety electrical

The new floating voltage in these ranges can be programmed to be 4.2 V, 4.1 V or 4.05 V (±

30 mV), as reported in

Appendix B.

Once the reduced floating voltage is reached, the charge terminates only if the battery

temperature is in the 10 °C ~ 45 °C range. If the temperature is outside this range, the

charger holds and restarts once the temperature decreases.

This function can be enabled/disabled setting a bit in NVM.

There is also the possibility to halve the charging current (see

Figure 6, blue dashed line) in

fast-charge in all temperature ranges.

In addition, all thresholds have an hysteresis: TLO and THO have a fixed hysteresis of 2 °C,

whereas TL, TH and THH have a programmable hysteresis of 2 °C or 5 °C (value set by a bit

in NVM).

If the temperature moves above TH or below TL, Vfloat is reduced. When the temperature

goes back inside the range TL-TH (with the associated hysteresis), Vfloat is replaced to its

maximum value.

At the beginning of the charge, when the battery pack is inserted, a check of battery

temperature is performed: if the temperature is outside the range 0 °C~45 °C, the charger

doesn't start charging and waits until the temperature goes back into the range (above 0 °C

or below 43 °C) (see

Figure 8).

Similarly, if auto-recharge is active and battery voltage decreases below 3.9 V, but its

temperature is outside the range 0 °C ~ 45 °C, the charge is stopped and restarts only when

battery temperature goes into the range 0 °C ~ 43 °C. In this situation, LEDs continue to

show “charge completed”.

During charging, if battery temperature goes outside the functional range (-2 °C ~ 60 °C),

the charger must stop the operations regardless of the current state. In this case, the LEDs

show “Battery temperature alarm” but the timers keep on counting. If the temperature moves

back inside the range 0 °C ~ 43 °C, the charger restarts the operations restoring the status it

was in before the interruption.

In this case, if temperature goes above 60 °C twice, the charger stops, the LEDs show a

“charge completed” and it is necessary to remove the battery to restart the operations (see

Figure 9). With the battery uninstalled, the LED configuration is like that indicated in

Appendix E.

In summary, the STBC21 behavior can also be represented as the following V-I

characteristic:

AM10417v 1

VFLOAT

I CHARGE

TLO

TH THH

THO

Temperature

CV- 1

CV- 2

CV- 3 CV- 4

I CHARGE

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