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TPS568215: Using VREG5 to power external logic/Ouput discharge

Elder Costa17
Expert 2825 points
Part Number: TPS568215

Hello,

I need a voltage source to supply some external logic to support a sequencer and output discharge (more on the latter below).

Could I use VREG5 for that? I am talking about a few miliamps worth of current.

Regarding output discharge, I understand there is an internal switch that puts a 500R resistance to ground to discharge the output voltage. Is that understanding right? If so, I will need an external discharger anyway as some rails where I am going to use this part have substantial amount of capacitance and I want to be able to fully discharge it in a few tenths of miliseconds.

Thank you in advance.

  • 0
    TI__Expert 3480 points
    1) If there is a discharge path on the VREG5 rail that can pull a current higher than the internal LDO's current limit (ILIM5) from the VREG5, then the VREG5 LDO turns off thereby shutting down the output of TPS568215.
    2)The discharge time is decided by 500ohm and output cap. If you want to discharge more quickly, you should use other ways.
  • 0
    TI__Expert 5745 points

    For the 500R discharge switch, it only happen during any event of fault like output overvoltage, output undervoltage , TSD , if VREG5 voltage below the UVLO and when the EN pin voltage (VEN) is below the turn-on threshold.

    If you want to use VREG5 to power the output discharge circuit, you must make sure the current is less than the ILIM5. If the current is too big, it may damage the internal LDO and the IC will be failed

  • 0 in reply to Vental Mao
    Expert 2825 points
    Hello Gavin and Vental, thank you for your answers.

    The current is of a few miliamps (maximum) to bias pull-up resistors and some tinylogic gates.

    However it ocurred to me that VREG5 is also disabled when EN is bellow threshold. Thus I will have to add an external LDO for the design to work as intended.

    Thank you both for your support.