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TPS562207S: Looking for a buck without that usual 'min. voltage' restriction

GGA
Genius 3875 points
Part Number: TPS562207S
Other Parts Discussed in Thread: TPS62122, , TPS62901, LM2621

Hi,

using TPS 62122 quite a while in an application, where
VIN might vary from 2V - 12V, required VOUT is 2.3 - 3.6V - or whatever VIN does deliver (pass through); current is max. 100mA.

Now we have a very cost sensitive application where we need something else, but all the bucks I find do have a min. voltage at ~4V; below it they switch off.

Is that intepreation right and how come? Why don't they just bypass if VIN gets below programmed VOUT?

And: most important, do you have a hint which buck I could look at?

thx. a lot

  • 0
    TI__Expert 7490 points

    Hi,

    Buck can't support VIN lower than VOUT. You should use a buck-boost for your application. Can you accept a buck-boost? If so, I can transfer this thread to TI other team for help.

    Thanks,

    Lishuang

  • 0
    Genius 3875 points

    Hi,

    but there are bucks that go down to 2V, like 62122 and I want to understand, why bucks don't just pass through whenever VIN < VOUT?
    Today 62122 is used exactly that way: output is set to 3.3V, and whenever VIN goes below VOUT just follows VIN.

    But if necessary, pls. pass this request to another TI team.

    What we need: VIN 2-12V, 100mA, VOUT: 3.3V if VIN is high enough, otherwise VOUT=VIN; QFN or similar, price <=0,5$

  • 0 in reply to GGA
    TI__Expert 7490 points

    Hi GGA,

    If you can accept Vout follows VIN, not regulated, Yes, some bucks can support, like TPS62122.

    As we can check that VIN UVLO of TPS62122 are VIH=0.8V, VIL=0.6V respectively. For these lower UVLO parts, the internal circuit design is much more complex than higher UVLO such as 4V/3.6V, like TPS562207S.

    You can check TPS62901 which may be suitable.

    Thanks,

    Lishuang

  • 0 in reply to Lishuang Zhao
    Genius 3875 points

    Lishuang,

    thx. very much for your support.
    62901 is a brilliant part, but even more expensive than 62122 PLUS it needs 3V VIN_min.

    Thinking about it, a step-up might have advantages for us: our VIN varies from up to 12V down to batteries with 1.5V

    A part like TI LM2621 could be a good compromise. But it doesn't fit pricewise.

    Perhaps you have a better hint?

    The ideal solution would be (100mA, QFN or similar, price < 0.5$):
    a. either VIN 2-12V, VOUT: 3.3V if VIN is high enough, otherwise VOUT=VIN; 
    or
    b. VIN 1.2-12V, VOUT: 3.3V;

  • 0 in reply to GGA
    TI__Expert 7490 points

    Hi GGA,

    Sorry for missing TPS62901 is 3V VIN_Min. Yes, maybe LM2621 a good compromise.

    Let's wait my colleague feedback. Please wait.

    Thanks,

    Lishuang

  • 0 in reply to Lishuang Zhao
    TI__Genius 16285 points

    Yup no 1.2V Vinmin buck that I can find for this application. I have requested the boost converter team to take a look and suggest options.