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BQ2002: USB charger with 2 series AA NiMH

Harry Li74
Intellectual 470 points
Part Number: BQ2002
Other Parts Discussed in Thread: LM317, BQ25600D, BQ25600DEVM-771, BQ25895

Hi trying to design a handheld device powered by 2 NiMH cells. And USB is required to charge the 2 NiMH cells when connected.

Is BQ2002 the best option?

And I’m most likely will not put a thermistor in the design, does the bq2002 work without a thermistor?

And also the room on my circuit board is limited, can you recommend a charging IC that will yield a simpler or just physically small circuit? The bq2002 evaluation board (DV2002L2/TL2) looks very big, I assume the big heatsink is for the LM317? Can you recommend a smaller replacement for LM317 to power from USB 5V?

  • 0
    TI__Genius 10240 points
    Hi Harry,

    BQ2002 does not have USB detection. If you are familiar with micro controller, you might want to consider to program the charger bq25600D for NiMH charging profile. It is not an easy task but it might be the best options - BQ25600D will give you USB D+D- detection for adaptor current capability; No heat sink is needed due to the high efficiency; BQ25600D in 2.0mmx 2.4mm WCSP package offers you small solution size.

    Best regards,

    Eric
  • 0 in reply to ezhao
    Intellectual 470 points

    Thank you,

    I think the BQ25600D is a better solution too. I'm good with micro controllers, just not that familiar with USB. And I have a few more questions.

    I have read through the BQ25600D datasheet and evaluation board document, and they didn't mention anything about NiMH charging. Where can I find the documentation relating to NiMH charging and instructions on how to set it to NiMH profile?

    And I need the USB D+ and D- for data between the PC and the micro controller, PC will be the Host. And BQ256000 will use the D+ and D- lines for detection only right? BQ256000 won't affect the communication between the PC and the micro correct?

    I'm planning to get the BQ25600DEVM-771 from digikey, can it be configured to charge NiMH?

    Cheers

  • 0 in reply to Harry Li74
    TI__Genius 10240 points
    Harry,

    The D+D- detection helps to find the current capability of USB ports, non-standard adaptors and DCP. The detection is done within the first 1 second after the VBUS is presented. D+D- will be high-Z after the detection. If the processor is able to high-Z DP/DM for the first second, then the charger D+/D- won't affect the communication between the PC and the micro. You can program the charging profile to charge NiMH battery. You can also check BQ25895 in QFN package with integrated ADC.

    Regards,

    Eric