STBC21 Datasheet, PDF (18/54 Pages) STMicroelectronics – LI+ battery charger with thermal regulation

Detailed description
STBC21
Figure 6.
Temperature ranges compatible with PSE, power safety electrical
CV- 1
CV- 2
CV- 3 CV- 4
AM10417v 1
V FLOAT
18/54
I CHARGE
I CHARGE
2
TLO TL
TH THH THO Temperature
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: T_LO and T_HO have a fixed hysteresis of 2 °C,
whereas T_L, T_H and T_HH have a programmable hysteresis of 2 °C or 5 °C (value set by a bit
in NVM).
If the temperature moves above T_H or below T_L, V_float is reduced. When the temperature
goes back inside the range T_L-T_H (with the associated hysteresis), V_float 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:
Doc ID 023256 Rev 1