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Original question:

TPS61094: Auto buck-boost mode is not working

TPS61094: will it do vin = 5v to vout = 3.3v?

frank boddeke
Prodigy 30 points
Part Number: TPS61094
Other Parts Discussed in Thread: TPS631000, TPS63901, TPS63900

i read this from some time ago (locked now, see linked thread):

Hi Jhon,

If VIN >= VOUT, the device works in pass-through or by-pass mode, no matter which mode the device is, the VOUT is close VIN, not the target voltage you set.

TPS61094 is a buck / boost device, it means it can work in boost mode (VIN to VOUT) OR buck mode (VOUT to SUP when charging).

I think what you need is buck-boost device (please be noted that buck / boost differs from buck-boost), like TPS63901 or TPS631000.

Regards, Nathan

the tps61094 datasheet does however have this example (5v to 3.3v)?? seems exactly the other way around? Vin > Vout, Vin buck to Vout

i need more or less what is in this figure 8-14. will it work? or do i need another part?

thanks

frank

  • 0
    TI__Genius 9545 points

    Hi Frank,

    When VIN > VOUT, vin doesn't buck to VOUT, VOUT follows VIN. The 'Buck' means that VIN will buck to SUP to charging supercap, not buck to VOUT.

    When VIN < VOUT, SUP will boost to VOUT to the target output voltage you set.

    So what is your requirement? Seems that TPS61094 is not a good option for you.

    Regards,

    Nathan

  • 0 in reply to Nathan Ding
    Prodigy 30 points

    hi nathan,

    how about the example in the datasheet? it shows 5v in and 3.3v out??

    is there another ic that can do this?

    my requirements:

    - 5v in, max 250ma

    - 3.3v out, average 150ma

    - large cap to supplement large current spikes on 3.3v application

    thanks

    frank

  • 0 in reply to frank boddeke
    TI__Genius 9545 points

    Hi Frank,

    The 3.3V in d/s here actually means that it can support 3.3V in charging mode, not buck mode. Maybe there is a little confused here... TPS61094 can only support 3.3V in charging mode, but in buck mode, the VOUT follows VIN, can't be a stable 3.3V.

    Sorry we don't have a integrated IC that can meet you requirements. Maybe you can consider a separated solution, by using a Buck IC (for 5V to 3.3V)  + Boost IC (for cap to 3.3V) + charging IC (or LDO, for charging the large cap).

    Regards,

    Nathan

  • 0 in reply to Nathan Ding
    Prodigy 30 points

    how about the TPS63900?

    that seems to do the trick?

    thanks

    frank

  • 0 in reply to frank boddeke
    TI__Genius 9545 points

    Hi Frank,

    TPS63900 can work for 5V to 3.3V and cap to 3.3V, but it can't charging the super cap, you still need a charger IC or a separated charger circuit.

    Regards,

    Nathan