BQ24045 Charging current Clarification

Hi Ivan,

BQ24045 can support fast charge current at 30mA using a resistor above what is recommended on datasheet.However, we only guarantee the termination current accuracy down to 6mA for this device. Therefore, if you charge at 30mA, it is not recommended to set the termination percentage lower than 20%.

Thanks,

Wenjia

HI Wenjia

Thanks for the advise.

Ivan

HI Wenjia

To confirm, we cannot float the Preterm pin then?

Ivan

You can still float Preterm pin - it won't affect the normal fast charge, just the termination current can not be accurately programmed to 10% of the 30mA.

If you need a lower termination level, bq25100H is our latest linear charger that can terminate at 1mA and looks like an ideal option for 30mA charge rate.

Thanks,

Wenjia

HI Wen Jia,

Our battery  capacity is actually 41mAh, so can we set the value to 4mA?

The only thing that TI cannot guarantee the termination current accuracy.

Hi XJ,

Yes you can program the termination to 4mA but the accuracy will not be as good as the spec on datasheet. Also, as the accuracy can not be guaranteed, it is possible that the part will not terminate because of the error.

Again, it is not recommended to program the termination current below 6mA and if it is a necessity, bq25100H is the best choice.

Thanks,

Wenjia

Hi Wenjia

Like to follow up with another question.

The customer is using 30mA as the fast charge current, and would like to set Iterm 5mA.

Would it be advisable to float the Iterm pin?

Ivan 

Hi Ivan,

If you are talking about bq24045, floating ITERM pin will program termination current to 10% of the fast charge current. So ideally, with 30mA fast chg current, Iterm will be 3mA. However, again, this device cannot accurate terminate below 6mA, so float ITERM pin cannot terminate chg at 5mA or 3mA.

At 5mA termination level, still bq25100H will be the best choice.

Thanks,

Wenjia

Hi Wenjia

Thanks for the advise. 

The problem faced now is that some parts are not terminating at all. 

Would like to check with you.

Another observation is the TS pin and battery pack

The battery pack that the customer does not provide a NTC output, instead it is providing a voltage proportional to the battery voltage which is input to the TS pin. There is an internal battery pack resistor at 33k and the customer is connecting an external 237K resistor. As the input profile is not of a typical NTC thermistor, Is there any possible impact that would cause the part to not terminate charge.

Could another possibility of a termination current be set at 1mA (due to the unguaranteed accuracy) therefore result in a non termination scenario?

Ivan

Ivan,

If the programmed termination current is less than 6mA, it is possible that the device will never terminate charging. When the input voltage to TS pin is above 1.6V, the device will disable safety timer and termination.

Thanks,

Wenjia

HI Wenjia

Noted with thanks.

One more question, if the termination current is set at less than 6mA where the inaccuracy occurs. Would the setting be a positive tolerance or plus.minus tolerance.

Example: I term set at 3mA, it could be 3,4,5mA (positvie) or 1,2,3,4,5 (plus/minus around 3mA) 

 Ivan