Hi,
I'm Marco Pappalardo from Bycare Lab S.r.l.s. We are designing a device with a wireless power receiver.
We have designed a mixed wireless and USB-powered charger, taking the idea from TIDA-00669 reference design and BQ51050B datasheet.
I have four questions, I will explain my doubts below.
Reading the TIDA-00669 reference design:
"The gauge is capable of self-correcting, accurately gauging and monitoring an alternate battery when connected to a compatible LI-ion or Li-Polymer battery with a range of 3.0V min to 4.2V max and a current capacity of 1000mAh to 2000mAh. The user must verify that the battery can be charged and discharged with the existing settings 500mAh charge rate or change the settings of this booster pack appropriately."
But in the BQ27421-G1A datasheet it is written that the "Recommended Sense Resistor input current" could be 2000 mA for "Long term RMS, average device utilization", 2500mA for "Peak RMS current, 10% device utilization" and 3500 mA maximum for "Peak pulsed current, 250 ms 1% device utilization".
1) I have to use a 2200mAh Li-Ion battery, because I have absorption peaks of 2A, 250ms, due to the GSM module. Could I use it or not in my design? Looking to the reference it is not possible, but in the gauge datasheet it seems possible (due to the fact that I have only short-term peaks only during transmission and startup of GSM module).
2) Does the BQ27412-G1A allow to pass 2-2.1A current from SRX to BAT pin?
3) Using a 2200mAh battery would allow the system works but, maybe, the gauge will give me the full charge indication until the charge value goes under 2000mA?
In my mixed design I use a BQ51050B for wireless charging and a BQ24040 for USB charging, using the scheme in BQ51050B datasheet. I insert in my scheme the BQ27421-G1A as fuel gauge. I would like to use NTC monitoring not only for the BQ24040 but also for the correction of residual charge made by BQ27421-G1A. For this reason I've connected:
- TS pin of BQ24040 to the NTC
- BIN pin of BQ27421-G1A to the NTC through a 1.8-MΩ pullup resistor to VDD.
NTC is a 10kΩ thermistor.
4) Did I make it good or using two different connection to the NTC corrupt the reading of NTC resistance and the correct system operation?
Thank you for your response,
Marco