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BQ25895: Query on BQ25895 battery charger CDP detection

USHA M
Intellectual 290 points
Part Number: BQ25895

Hi Team,

We are using BQ25895 battery charger in our product design. 

When we are connecting a USB charger cable from the PC(USB charger port) to our unit, it is getting detected as SDP and the charge current will be limited to 500mA. With USB power bank, sometimes it detects as CDP port, but the detection is not consistent.
There is a document regarding the CDP mode limitation(refer the attachment), but this is not available in TI website as errata for BQ25895 IC. In this document, limitation w.r.t. CDP mode detection is mentioned. But, the workaround is not available. Can you please let us know is there any workaround for this?   
--
Thanks,
Usha
1768.bq2589x_DSEL_CDP_limitation.pdf
  • 0
    TI__Guru**** 166896 points
    Hi Usha,

    Unfortunately, the CDP detection algorithm per USB BC1.2 spec has not been implemented consistently by electronics manufacturers. The only workaround is for the host processor to perform full enumeration on the USB bus as recommended by the USB BC 1.2 spec. Is 500mA input current not enough for your host to power up and perform enumeration? If not, then you could ignore the BC 1.2 spec, short D+=D- and use the ILIM pin to set the minimum current at power up. The charger has VINDPM and ICO features which will prevent it from crashing its input rail.
  • 0 in reply to Jeff F
    Intellectual 270 points

    Hi Jeff,

    Thanks for the reply.

    Therefore the only workaround to detect CDP on BQ25895, when BQ25895 is connected to a Laptop(PC) is to perform full enumeration on the USB bus by the laptop as recommended by the USB BC 1.2 spec.

    Is my understanding correct?

    Just being curious! How do CDP work on laptops with mobile phones?

    Regards,
    Gireesh

  • 0 in reply to Gireesh Nair40
    TI__Guru**** 166896 points
    Gireesh,

    Yes. I suspect that laptops with mobile phones plugged in are enumerating.