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TPS61178: suggestion for alternative with higher Vmax, boost or even buck-boost IC

Bradley Johnson
Prodigy 40 points
Part Number: TPS61178
Other Parts Discussed in Thread: TPS552892, TPS61376, TPS61377

Tool/software:

Hi, I have two related questions.

The TPS61178 recommended maximum voltage is 20V, and 23V absolute maximum. Can you suggest a similar boost converter IC (sync w/ integrated FET) that has higher Vmax, at least 25V or even 28V. In some scenarios noise backfeeding on the output can exceed 23V. The output is clamped with a TVS with Vmax 24.4V. The TVS voltage cannot be reduced or it would conduct during normal operation. The TVS absorbs some but not all of the transients, but unfortunately the TPS61178 occasionally receives > 23V which we believe explains several failed ICs. We have added a diode on the output to block the transient high voltage, but this causes power loss. A converter with higher Vmax (25V or even 28V) may allow eliminating the diode.

The current design uses 12-15V input, boost to 17V. Iout = 2.1 A, F~500 Khz, and the load disconnect is being used. 

Second question, instead of a boost converter, what about replacing the TPS61178 with a buck-boost that has a larger input range, 12-32V or even 12-36V with output of 17V, 2.1A. Something like TPS552892, which has Vmax of 36V. This would have the beneficial side effect of allowing much wider input range.

  • +1
    TI__Genius 12505 points

    Hi Bradley,

    Thanks for the reaching out.

    There may be two alternative solutions for higher Vmax, the one is TPS61377, which is a 25V sync integrated Boost but w/o the load disconnect, the other one is TPS61376, 1 25V Boost with load disconnect but a non-sync Boost. Unfortunately we don't have a 25V sync boost with load disconnect solution now.

    Also for buck-boost, I believe TPS552892 is the best solution for 12-36V to 17V/2.1A output.

    Hope this can answer your question.

    Regards,

    Nathan 

  • 0 in reply to Nathan Ding
    Prodigy 40 points

    Thanks, I'll take a look at the TPS552892 and test with the EVM. Anything in particular I should look at carefully when considering the buck-boost topology?  particularly in regard to the timing of periodic voltage transients that could cause the converter to change between buck and boost modes?

  • 0 in reply to Bradley Johnson
    TI__Genius 12505 points

    Hi Bradley,

    The layout should be a importance point for buck-boost converter, this AN can give you a simple start about the layout guideline, please refer to it and make sure your layout is followed the guidelines. https://www.ti.com/lit/an/slvaer0b/slvaer0b.pdf

    For other buck-boost questions, let me loop buck-boost expert Bryce to help to answer.

    Regards,

    Nathan