Tool/software:
Hi Team,
Could you please advise: Does Ti have protection IC for LIC(Lithium-ion capacitor), which function is similar with BQ2970?
Requirement:
UVP(over discharge detection): 2.5V
OVP(over charge detection): 3.8V
Best regards,
Terry Hu
Hi Terry,
The closest part TI has is the BQ29706, with a OVP of 3.85V and UVP of 2.5V.
Best regards,
Thomas Rainey
Hi Thomas,
For BQ29706, the hysteresis voltage for OVP is 100mV±20mV, the hysteresis voltage for UVP is 100mV±50mV, correct?
Another question, to release the over discharge state, why should the device detects V- higher or lower than -0.7V to determine adding the hysteresis voltage or not? Why should the value be -0.7V?
Does V- lower than -0.7V indicate a charging overcurrent through the body diode of EXT DSG MOSFET?
best regards,
Terry
Hi Terry,
You are correct, the BQ29706 has hysteresis voltage of 100mV ± 20mV for OVP and hysteresis voltage of 100mV ± 50mV for UVP.
V- is based on the difference between the cell voltage and the charger voltage. The value for V- comes from the internal design of the part.
If V- is higher than -0.7V, the charger voltage is lower than the cell voltage. In this case the cell voltage will need to reach the voltage of UVP plus hysteresis. This is because if the discharge is turned back on right after it reaches UVP then the cell could drain and drop below UVP right away causing an endless cycle of turning on and off the discharge and never charging the battery.
If V- is lower than -0.7V then the charger voltage is higher than the cell voltage. In this case there isn't concern with the cell discharging faster than it can charge.
You are correct, the drop across the body diode would indicate a charging current. However, charge overcurrent status is disabled during over-discharge status because of that reason:
