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TPS54620: TPS54620RGYT query

AMIT JAGTAP
Prodigy 10 points
Part Number: TPS54620
Other Parts Discussed in Thread: UCD9090A,

We are using TPS54620RGYT for generating Negative voltage supply but we encountered that we are not able to control the Converter with the Enable pin .

For Enable signal we are using UCD9090A which is able to control other Power Converters , please find below the Image and Design and provide comments :

As you can observe output is enabled even after the enable is Toggling .

  • 0
    TI__Mastermind 35165 points

    Hi Amit,

    With the inverting buck-boost configuration it is important to remember the TPS54620 device ground reference is -Vout. This means EN relative to -Vout needs to be below the EN threshold to turn off the TPS54620.

    Is channel 1 the EN signal? Between time 0 and ~15ms, is the UCD9090A output floating?

    It looks like the EN pin may be floating high initially due to the TPS54620's internal pull-up current source. Then when -Vout gets near ~4V, the EN signal is clamped approximately a diode drop below ground. I will guess this is getting clamped by the ESD diode on the UCD9090A pin connected to the TPS54620 EN.

    For levelshifting the EN pin, you may find the two application notes below useful. The second one has a simpler levelshifting circuit which should be suitable for this use case.

    https://www.ti.com/lit/an/slva540/slva540.pdf

    https://www.ti.com/lit/an/snva856a/snva856a.pdf#page=12