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TPS63060: Buck mode current sinking capabilities

Fabian Geissler
Prodigy 20 points
Part Number: TPS63060
Other Parts Discussed in Thread: TPS63070

Hello,

I am trying to build a TEC driver similar to this Application Report: www.ti.com/lit/an/slva677/slva677.pdf

My input voltage is in the range of 8V to 12V, so I can not use the same converter as in the report. Instead I built it with the TPS63060 as I thought they would behave alike.

In boost mode everything works fine, current output up to 200mA -- more is not necessary and not tested.

Buck mode on the other hand does not work. TEC current has a maximum of around 30mA, feedback voltage diverges from the 0.5V reference. Setting the output voltage without load works. After double checking everything I do now think that the problem might originate in TPS63060 current limiting or something similar that prevents operating as current sink in buck mode.

Is my assumption, that the TPS63060 is not capable of sinking current in buck mode, correct? If so, what other part can you recommend for the job?

Thank you!

  • 0
    TI__Expert 7925 points
    Hi Fabian,

    The maximum Vout for TPS63060 is 8 V. If your input is 8-12 V it should never operate in boost mode. Are you sure you are not confusing buck and boost mode?

    The TPS63060 can sink current, but make sure it is operating in forced PWM mode (PS/SYNC connected to VIN), not in PFM mode. The negative current limit is not specified, if current limiting is needed we recommend using TPS63070.

    Best regards,
    Milos
  • 0 in reply to Milos
    TI__Mastermind 20900 points
    Hi Fabian,

    I'm going to close the thread due to inactivity, but please post back if you have more information or further questions.

    Regards,
    Julian
  • 0 in reply to Milos
    Prodigy 20 points
    Sorry for the late reply,

    I must have missed the 8V maximum output voltage. But that is no problem, we can reduce the input voltage range, as we will use it just for some lab tests.

    Also I think I made a mistake while quickly measuring the output current after assembly. In a more extensive measuring session with 6V input voltage everything worked up to 800mA TEC current in boost mode (source) and down to -350mA in buck mode (sink).

    The TPS63070 has a specified "Negative Input Current Limit", I guess that applies to operation as output sink? In that case it would be able to sink more current than the TPS63060. Or is there another limit to the sinkable current?

    Thank You!
    Fabian