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TPS81256: Squeeze out a little more output current? Or level a 200ms intermittent load?

apullin
Intellectual 575 points
Part Number: TPS81256

Hi,

I am using TPS81256 modules in a design to generate a 5v rail that I need in a portable device running from a single cell li-ion battery.
I am running at the limits of what the module can do, and I suspect that at the low voltage range of the battery, I am hitting current limited mode.

The problem is an intermittent 100-200ms load (IR lamp) that pulls the total system current draw right up to around 550-600mA, from the ~400mA idle.

Is there anything to do to eek out a little more performance from this module? If the modules support synchronous operation, adding a second regulator might be an option, since it is already so small. Or running with multiple separated 5v rails.

Also, any recommendation on how to level out a load like that would be appreciated. I am barely a sophomore when it comes to proper power design!

Interestingly, this module is pretty much the only one I could find to suit my needs, 2.7v-4.2v input with fixed 5v output in a reasonably small self-contained package. Murata has one, but they are out of stock everyone on the planet. So if TI just made another version of this module with slightly beefier limits and could stay in this size range, that would be super ... 

Thanks,
Andrew

  • 0
    TI__Guru 59001 points
    Hello
    It seems there is no way to increase average input current limit from the outside.
    Because input current is inverse proportional with input voltage, reducing input resistance (wire resistance , contact resistance, pattern resistance) may help.
    Thanks
  • 0 in reply to EricLee
    Intellectual 575 points
    Thanks for the feedback. I think the best option I have is to revise the design to move to the converter as close to the point of load as possible, which ends up running a large battery-voltage polygon on the board, but that can be accomodated. And I am going to add provisions to run two split +5v busses, with a dedicated converter for each one, to split the load.