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BQ51050b charging pad detect

Ed Walker
Prodigy 5 points
Other Parts Discussed in Thread: BQ51010B, BQ51050B, BQ51021

Hello Forum, is there a signal that I can use from the BQ51010B to indicate when it is on the charging pad?
That's all I need to know, that my wireless receiver product is on the pad.

I see this note in the data sheet.

The bq5105x provides one status output, CHG. This output is an open-drain NMOS device that is rated to 20 V.
The open-drain FET connected to the CHG pin will be turned on whenever the output (BAT) of the charger is
enabled. As a note, the output of the charger supply will not be enabled if the VRECT-REG does not converge to the
no-load target voltage.

Will CHG tell me I am on an active charging pad?

Thank you.

  • 0
    TI__Genius 14890 points

    Ed,

    The title suggests bq51050B and the note mentions bq51010B.  They are slightly different and I'll explain both for clarity.

    When the RX is on the pad, the RECT pin shows the rectified voltage.  That's the first indication of power.  As long as the RX is on the pad and does not send an End Power Transfer (EPT) packet, RECT will continue to be active.  The RX will negotiate with the TX to get the correct RECT voltage.  When that is reached, the output will be enabled.

    The bq51010B outputs 7V when on the pad.  The /WPG pin will drive low when OUT is enabled.

    The bq51050B is a bit more involved since it's expecting a battery on the output.  Assuming there's a battery, the /CHG pin will drive low when BAT is enabled.

    Once the bq51050B goes through the charging cycle and terminates charging, it will send a "Charge Complete" EPT and the transmitter will terminate it's power delivery.  In that case, CHG is off, but the RX is still on the pad.

    Depending on the TX, it will still send a PING which will enable RECT enough to determine if the EPT is still valid. If it is, the EPT will be resent and OUT/BAT will never turn on and CHG/WPG will never enable either.  If EPT is not valid, power transfer will resume.

    See the bq51021 for discussion of the PD_DET and TMEM pins.  The TMEM pin has an RC network that keeps the PD_DET pin low which can also indicate still on the pad (but not active).

    Long answer for a simple question.  Let me know if you need anything else.

    Regards,

    Dick