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TPS43060 - Allowing Reverse Current

Tim-Oliwer Meyer
Prodigy 10 points
Other Parts Discussed in Thread: TPS43060, TPS43060EVM-199, TPS43000, TPS43061, LM5122

Hello,

during my thesis I'm using the swichting regulator TPS43060 with the evaluation board TPS43060EVM-199.
For my application, bidirectional current is needed. Thus I'm asking for a modification of the circuit, which allows me to use the swichting regulator with reverse current.

It's for prototyping purposes, so the current sensing or the current limitation does'nt neccessarily need to work. The only requirement is that the swichting regulator works fine and allows reverse current.

Thanks for your help!

Tim

  • 0
    TI__Mastermind 35185 points

    Hi Tim,

    By allowing reverse current do you mean that you need it to allow CCM operation? It's possible to trick the IC to avoid diode emulation by adding an offset in the ISNS signals to keep it above the zero cross detect threshold. Using the bias current of the current sense pins, putting a larger resistor in series with the ISNS- line will add DC offset.

    Best Regards,
    Anthony

  • 0 in reply to Anthony F
    Prodigy 215 points

    I was wondering why the TPS43060/61 did not offer a pin programmable option to force CCM.  I actually use that for high power applications since the the power savings of DCM operation are not necessary and it keeps open circuit voltage closer to loaded voltage.  On the TPS43000, I've had problems with noise under light loads when allowing the part to run in DCM with PFM.  I force CCM on that one and it works a lot better.

    Anyway, I was thinking of using the TPS43061 in a higher power design so that's a handy trick to force CCM.  I'll try that.

  • 0 in reply to CraigHB
    TI__Mastermind 35185 points

    One thing to keep in mind when doing this is that adding the offset will also reduce the maximum peak current limit. The sense resistors will need to be sized accordingly.

  • 0 in reply to Anthony F
    Prodigy 215 points

    Sounds a bit tricky.  I need a pretty high current limit already and with inductor DCR sensing, there's not much wiggle room.

  • 0 in reply to CraigHB
    TI__Mastermind 35185 points

    I agree with DCR sensing it may be a bit tricky depending how much margin you have from the current limit at full load. The pulse skipping mode operation of the TPS43061 operates a differently than the TPS43000 so you may not have the same issues. You may not need the offset or you might be able to balance it out where you put in enough offset to at least avoid pulse skip mode and still be able to reach the maximum current.

    If you absolutely need CCM operation the LM5122 will allow you to do this more easily as it does have the mode pin.

  • 0 in reply to Anthony F
    Prodigy 215 points

    Probably not a big deal to allow it to pulse skip, just better with forced CCM.  Doesn't look like the LM5122 does inductor DCR current sensing, does it?  That's kind of a biggie, waste of power to use a current sense resistor plus they take up a lot of PCB real estate.  Space is a real premium for my design, TPS43061 uses a much smaller package and does not require a sense resistor.