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TPS54620: change Vout dynamically between Vout min and Vout max: use Tracking vs FB ?

AnBer
Mastermind 30110 points
Part Number: TPS54620
Other Parts Discussed in Thread: TPS54622, TPS54824

Team,

The use case is to change Vout at run time (to have comparable behavior as a lab power supply and select a specific Vout value over time).

-Would both Track and FB allow to change Vout between Vout min and Vout max at run time?
-Is it better to use the track or the FB pin for this? What would be the differences between using one of the other?

Do we have a DCDC that would enable to change Vout between 0V a Vout max of 8V @ 5A via tracking?

Thanks in advance,

A.

  • 0
    TI__Mastermind 35165 points

    Hi ,

    I think using the Track pin might be the simpler solution but there are some tradeoffs to be aware of if this pin is used.

    1. There is some offset between the SS/TRK pin and the regulator FB voltage (30 mV typical) so the output voltage regulation is slightly less accurate.
    2. The SS/TRK pin needs to go above 1.4V worst case for the PWRGD pin to go high.
    3. There is a knee in the SS/TRK vs FB voltage as the SS/TRK voltage approaches 0.8V. This transition happens from ~0.7V to ~1.1V on SS/TRK. I have pointed this out in the waveform below from the datasheet. The TPS54622 (or the newer TPS54824) would have a sharper knee if this is a problem.

    I think these devices are the only ones with the tracking feature to meet this requirement. So, another advantage of doing this through the FB pin is it would enable some additional solutions. However another one of the requirements for this application which starts to limit the devices that can be used is the 8-V output.

    Will the SS/TRK pin meet the needs here or would they need to do something through the FB pin?