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TPS62743: Help with selecting devices.

EEngineer505
Prodigy 590 points
Part Number: TPS62743
Other Parts Discussed in Thread: TPS63000, TPS63050, TPS62730, TPS61291, TPS62740

I've looked at TPS62743 for some time. 

I am wondering if there is anything similar that also has a boost output in series with the buck?

That is to say, the power goes from a 3V battery to either the boost or buck, and then output of that goes to the other... so either battery -> buck -> boost, or battery -> boost -> buck. I suppose a boost with an integrated LDO could work too.

Target voltage is 2.1V, but we would be open to other voltages between 2.5V and 2.1V.

Thank you for help!

  • 0
    TI__Guru*** 146640 points
    Hmm, would a buck-boost like TPS63050 or TPS63000 (lower Vin) work? Is ultra-low Iq needed?

    TPS62730 is sometimes used in these applications.
  • 0 in reply to Chris Glaser
    TI__Prodigy 590 points
    Hi Chris,

    Ultra Low Iq is needed. Battery is a 3V coin cell, and needs to last as long as possible.
  • 0 in reply to EEngineer505
    TI__Guru*** 146640 points
    What is the minimum and maximum load current? Can they accept the bypass mode of the TPS62730? (There's also the TPS61291 which does the same thing but with a boost.) What voltage do they want to drain the battery down to?
  • 0 in reply to Chris Glaser
    TI__Prodigy 590 points
    A buck/boost may work.

    TPS61291 has low current in bypass mode, but fairly high current in boost mode. We currently have a boost in our system (with 300nA Iq in boost mode), and we're looking at a design that also uses a buck. If there is a buck-boost that can output 2 voltage rails (one from the buck, one from the boost), that's something we can take a look at as well, but the main point of interest is around the buck.

    Ideally we would be able to drain the battery down to at least 2.2V, if not all the way to 2.0V.
    Minimum load current out of the buck would be 5-10uA, max would be ~100mA, but only at the very first turn-on. After that the max should be maybe 10-20mA.
    The boost would need to support output currents of 100mA for 100us pulses, at rates up to 200Hz.
  • 0 in reply to EEngineer505
    TI__Guru*** 146640 points
    No, there is no 2 channel device which makes sense for your application.

    Based on your voltages, just a buck to 2.1V would be needed. TPS62740/3 could be used for this. I don't see why you need a boost, unless you just want to discharge the battery a tiny bit more.