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BQ25792EVM: BQ25792RQM

Agxin Justin xavier
Intellectual 370 points
Part Number: BQ25792EVM
Other Parts Discussed in Thread: BQ25792, BQ25798

I am trying to design a USBC or /and POE powered Product the USB PD has  IC TPS25750DRJKR 

which supports source and sink mode ..the POE power is from a POE dc-dc MODULE which provides 24 V input to one of the vin and USBC through CC is connected through other VIN

The two inputs I am planning to connect it to the BQ25792RQM .there are use cases where I may not use the battery but the System need to be powered through any one of the power path and the power path selection and priority is required .So Is it possible to implement a use case with out VBAT 

If Lets say  I provide Input voltage through a External regulator which through ORING  diode  at input can power on the REGN to 5V

but V bat is not present can the IC be active and select one of the path based on register setting ? 

I mean Dead bat is supported by TPS25750DRJKR (powered though Vbus )

same way if a simple oring diode from POE and USB and LDO with diode at o/p connected to the REGN Pin of BQ25792RQM will it work without bat ?

does REGIN supports external 5V in ?

  • 0
    Intellectual 370 points

    Since my CC controller can be active without bat , The LDO for the CC controller 3.3v will also be powered by the oring input so I can enable the path based on the available power 

  • 0 in reply to Agxin Justin xavier
    TI__Guru**** 166986 points

    HI Agxin,

    To prevent system crash, BQ25792 can be used without battery but charge should be disable by one of the following:

    1. /CE (charge enable) pin pulled high

    2.  Charge enable bit =0

    3.  TS pin fault due to missing thermistor

    alternatively, you can change to pin2pin and reg2reg BQ25798 which can operate without a battery and not have system crash.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Intellectual 370 points

    Hi Jeff

    thanks for the response  this can be done but the question here is how does the input power path works by default since the mosfet on the input path need to be driven to enable power to the system and the charge controller IC .. currently  I am not understanding how this will be done since vbat is not present and bus is also not present until I turn on the FET charge controller cannot get power through vbus and cc controller or host cannot communicate  with the battery charger IC please refer my earlier image attached 

    does Vbus and bat are the only power pins for the ic for the internal reg to work or vac 1 and vac 2 can also power the chip ? So that it can be active to drive the mosfet when any of the inputs are present 

  • 0 in reply to Agxin Justin xavier
    TI__Guru**** 166986 points

    Hi Agxin,

    Once VACx senses a voltage > UVLO even without I2C comms, the charger's related ACDRVx pin provides the voltage to turn on the AC/RB FETs with VAC1 having priority over VAC2 if both are tied together. 

    Regards,

    Jeff