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

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

  • 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

  • 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$

  • 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

  • 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;

  • 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

  • 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.