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TPS25948: The relationship EN pin and RCBCTRL pin.

tsubasa.hatada
Prodigy 100 points
Part Number: TPS25948

Tool/software:

Hi team,

I'm considering the USB power control circuit on DRP using TPS25948.

So, I would like to know the operation of EN pin and RCBCTRL on TPS25948 to control USB power path.

When RCBCTL is Low and the current flow is from OUT to IN (Reverse), is it necessary to enable EN pin?

According to Block diagram on Datasheets(page.20), TPS25948 has internal buck to buck FETs.

Therefore, I think that if only RCBCTL switch to Low, it is possible to flow the current from OUT to IN.

Thank you for your support.

  • 0
    TI__Mastermind 38945 points

    Hi Hatada-san,

    The body diode of these internal HFET and BFET are not designed for continuous current flow and can result in damage to device. The main current conduction always happens through the FET channel instead of body diodes. 

    During normal operation, both FET will turn on. During RCB operation, we will turn off the BFET when reverse current comes but when forward current comes, we sense it and turn on the BFET.

    When EN is off, both the FETs can be off so no current will flow. 

    If you pull the RCBCTRL to low, the device will not perform reverse current blocking so bidirectional current can flow (not just out to in).

    Let me know if you have any follow up questions.

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 100 points

    Hi Arush-san,

    Thank you for the information.

    I've understood about this eFuse operation.

    That means the internal FETs on TPS25948 are same to the body-diode on normal MOSFET. 

    I have one additional question.

    TPS25948 have two types of Pin4 configuration, FLT# (TPS259480) and RCBCTRL (TPS259481 or TPS259482).

    If using the type of FLT# (TPS259480), is it enable to Reverse Current Blocking function?

    Thank you for your support.

  • +1 in reply to tsubasa.hatada
    TI__Mastermind 38945 points

    HI Hatada-san,

    tsubasa.hatada said:
    That means the internal FETs on TPS25948 are same to the body-diode on normal MOSFET. 

    Yes.

    tsubasa.hatada said:

    TPS25948 have two types of Pin4 configuration, FLT# (TPS259480) and RCBCTRL (TPS259481 or TPS259482).

    If using the type of FLT# (TPS259480), is it enable to Reverse Current Blocking function?

    If you are using FLTb variant of TPS25948 then you won't be able to control RCB so by default it will be always on RCB. 

    Feel free to ask any follow up question.

    Best Regards,
    Arush