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TPS25830A-Q1: External 5V LDO connected to VCC

Kiyoshi Koyama
Intellectual 475 points
Part Number: TPS25830A-Q1

Hello support team,

If we connect an external 5V LDO to VCC for VCONN power, should we set the LDO output voltage between 5.25V and 5.5V? Or it would be OK even 5V?

Thanks,

  • 0
    TI__Expert 8980 points

    Hi, Kiyoshi,

    We suggest make it 5V, same as VCC voltage.

    Regards,

    Bob

  • 0 in reply to Bob Ma
    Intellectual 475 points

    Hi, Bob

    Thank you for your reply. But let me ask you one more question.

    Do I need to use an LDO to overdrive a VCC? Or can I use a switching regulator?

    If you say I can use a switching regulator, please tell me how much I should reduce the VCC ripple.

    Thanks,

  • 0 in reply to Kiyoshi Koyama
    TI__Expert 8980 points

    Hi, Kiyoshi-san,

    I suggest to use LDO to overdrive Vcc. Vcc is internal logic power supply, I afraid the DCDC ripple will cause some issues.

    Thank you.

  • 0 in reply to Bob Ma
    Intellectual 475 points

    Hi, Bob

    The data sheet says below in Section 10.3.16.4.

    "Failure to connect an external supply may cause TPS2583xA-Q1 Vcc reset. The device turns off
    when the junction temperature exceeds the thermal shutdown threshold"

    I'm worried if the external LDO voltage needs to be higher than the internal VCC LDO voltage.

    If the internal VCC LDO voltage is higher than the external LDO voltage, I'm concerned that the VCONN will be supplied from the internal LDO and the IC will shut down due to overtemperature.

    Thanks,

  • +1 in reply to Kiyoshi Koyama
    TI__Expert 8980 points

    Hi, Kiyoshi,

    Your consideration is correct, the external LDO should overdrive VCC, its output should not be lower than Vcc. Vcc range is from 4.75 to 5.25. You can set LDO output at 5.3V.

    Blow description from datasheet FYI.

    "In applications where VCONN support is required, the VCC pin can be over-driven with an external 5-V LDO
    capable of sourcing at least 300 mA. In this operating mode the external LDO is the source for the buck low-side
    switch gate drive as well as power to the internal VCONN mux.
    Note if using external 5-V LDO for VCONN power, the timing sequence below must be required. External VCONN
    power can not be enabled before the TPS2583x-Q1 is enabled, external VCONN must be disabled before the
    TPS2583x-Q1 is disabled. In real application, customer can tie the EN of external 5-V LDO and EN of
    TPS2583x-Q1 together to meet the timing requirement."

    Regards,

    Bob

  • 0 in reply to Bob Ma
    Intellectual 475 points

    Hi, Bob

    Thank you for your big help!