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Clarification on TPS65217 SYS out

Colin Bester
Prodigy 20 points

I am looking to confirm whether SYS (pins 7, 8) can be switched off when running under the following sequence:

  • Both 5V main and battery connected.
  • Bit 7 (OFF) of status register (0x0A) is set to a '1'
  • 5V mains supply is removed.
  • PWR_EN pulled low

I am seeing changes in VLDO outputs when but SYS pin stays at battery voltage and I am not sure if I am doing something wrong or whether this is expected behavior or not.

If this is expected behavior (i.e. SYS voltage stays high at battery voltage) what is recommended way to totally shutdown device - i.e., disconnect the battery?

Thanks

Colin

  • 0
    TI__Expert 4005 points

    Colin, 

    The battery is always connected to SYS regardless of the state of the device. From the datasheet, page 25:

    "In case AC or USB is not present or blocked by the power path control logic (e.g. in OFF state), the battery
    voltage always supplies the system (SYS pin)."

  • 0 in reply to Gregory Watkins
    Prodigy 20 points

    Thanks Greg, that's what I thought would be the case - confusion and a lot of hopeful wishing was statement regarding OFF state that all power rails are switched off.

    1) What then is thinking if one wants to add other peripherals, for example an LCD display with backlight display, what would be recommendation for supplying higher current draw of backlight and it's shutdown.

    Thanks

    Colin