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BQ24232 use case

Gautham
Genius 12485 points
Other Parts Discussed in Thread: BQ24232

Hi,

My PCB has a 100mAH, 3.7V Li Polymer battery and everything works great as expected! 

I am using the BQ24232 on my EVM and wanted to confirm this:

1. I have a variant of the same board which will support 2 AA batteries. I am wondering if the AA batteries can be connected to the BAT lines and have the CE high to disable charging.The USB may be connected when the AA are present but the BQ will not try and charge the AA because of a high CE condition. All it will do is either user the AA or the USB to power the load. The datasheet says OUT is active and just wanted to confirm.

2. Is there any other recommended protection required on the Li battery use case?

3. My board is supporting a 100mAh and a 1200mAh battery charging. I am charging only at 80mA Fast Charge and my timer is at maximum. The 1200 mAh battery will be charged only half way through before the timer expires. Can the user unplug/plugin the USB cable to reset the timer so that he can continue charging the rest of the 1200mAh battery? Both are 3.7V batteries btw.,

Sample schematic attached.

Appreciate the response.

Regards,

Gautham

 

  • 0
    TI__Genius 13700 points

    Hello Gautham,

    1.The supplement mode of the charger is active even when it is placed in standby which disables charging using the /CE pin. This would allow the AA batteries to serve as a power source with no adapter attached or as a supplement in the event the Vin droops below the voltage present on VBAT.

    2. It would be recommended to include battery gauging to protect the batteries from over discharge.
    One note is that using multiple battery types will complicate gauging.

    3. If the input voltage to the charger drops as a result of the input source being disconnected then the charge cycle will terminate and the timers will be cleared and the charger will attempt to begin a charge cycle. However this will cause the registers to be reset to the default values. It would be better if you could toggle the /CE.

    How is the battery capacity decided? It seems like there are three options. 2xAA, 100mAh, and 1200mAh. The AA do not want charging. The 100mAh wants lower current charging. If you were to retain control of the EN pins of the charge you could actively change the settings from Ilim setting the charging current to the preset 500mA charging.

  • 0
    TI__Guru**** 154206 points

     Regarding 1, with /CE high, charge is disabled but supplement mode is still available so the battery FET will turn on if a load transient is higher than the input current limit, tying BAT=OUT.  Is that okay?

    Regarding 2, the LiPo battery should have an internal protector.

    Regarding 3, unplugging/replugging will reset the timer.  Toggling /CE and USB Suspend Mode (EN1/EN2 both high) after the the timer expires will also reset the timer.

  • 0 in reply to Jeff F
    TI__Genius 12485 points

    Thanks Ryan, Jeff. 

    Ryan: Yes I have all the three batteries I am supporting. The Lithium batteries are for non public use whereas 2xAA will be the public version. I have a buck boost on the Battery Output which can take in as low as 2.5V and bring it upto 3.3V. In the public board, I will have the CE toggled to high to disable battery charging completely. All the BQ chip does is select the USB or the 2xAA to provide an un-interruptive power supply.

    Jeff: Thanks for your input. I will make sure that the LiPo has an internal protection PCB. 

    Regards,

    Gautham