• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 63 subscribers
  • Views 178 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS61236P: Need boost converter with pass-through for VIN>VOUT

Steve Fenwick1
Prodigy 250 points
Part Number: TPS61236P
Other Parts Discussed in Thread: TPS61023, , TPS61030, TPS63811

I need a boost converter for a 3.7V, 1A load (not switch current!) from a single LiPo cell that we want to run down to 3.0V. We also need this to operate when the system is being operated from a fresh battery at up to 4.35V VIN. The load can operate from 3.4V to 4.5V.

It looks like the TPS61023 would work, but I like the switch specs and availability of the TPS61236P a lot better. Would it work in this application? I think I don't care about CC mode.

The risk seems to be that the TPS61236P would enter pass-through when the battery voltage drops to near 3.7V. We could run at a higher voltage, up to 4.5V, to help avoid that; then we should stay out of pass-through if VIN is 3.9V or higher, and if it's that high and we lose up to 0.4V we might be ok. Given the low rDS(on) of the high-side switch, and choosing a low DCR inductor, I think we could keep the FET+inductor to 100mOhms or less, which should only cause about 0.1V of drop from Vin. But how low from the target VOUT does VIN have to fall before resuming switching? The full 0.6V?

The TPS61030 also looks like an option, but doesn't mention a pass-through mode at all.

What do you suggest? Thanks!

  • 0
    TI__Expert 7595 points

    Hi Steve,

    Thanks for reaching out. There is a little differences with TPS61236 and TPS61023 about pass-through mode.

    The TPS61236P may enter into pass-through operation prematurely when VIN = VOUT - 0.6V (so if your Vout is 3.7V, it will enter into pass-through mode when Vin is higher than 3.1V), and exits when VIN is below the threshold with a hysteresis, this threshold is not provided and I will test this in out bench later. 

    TPS61023 enter into pass-through mode when the input voltage is higher than the setting output voltage, so if VOUT=3.7V, it will enter into pass-through mode until VIN > 3.7V, and exits  when the output voltage drops below the 97% of the setting target voltage.

    TPS61030 do not have pass-through mode.

    Best Regards,

    Nathan Ding

  • 0 in reply to Nathan Ding
    Prodigy 250 points

    Thanks for the prompt reply. I looked a little more and the TPS68311 may be a better solution for this application. What do you think?

    Best,

    Steve

  • 0 in reply to Steve Fenwick1
    TI__Expert 7595 points

    Hi Steve,

    We do not find the TPS68311, are you sure there is no mistake about this part number?

    Best Regards,

    Nathan

  • 0 in reply to Nathan Ding
    Prodigy 250 points

    My  mistake: TPS63811. Thanks!

  • 0 in reply to Steve Fenwick1
    TI__Expert 7595 points

    Hi Steve,

    From my understanding, in your case, Vin=3.0~4.35V, Vout=3.7V, Iout=1A, right?

    TPS63811 is a buck-boost converter, of course it can be applied for this condition, but the Vout of this chip is set by I2C interface, rather than external resistor divider, which is different from TPS61236. I am not sure weather this will cause any trouble to you, if not, there is no problem, I think.

    Best Regards,

    Nathan Ding

  • 0 in reply to Nathan Ding
    Prodigy 250 points

    Thanks for the responses. We're going with the 63811; we have a micro that can manage it over I2C. If the 63810 comes back into availability, we might switch to that.

    Thanks!