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TPS552882: Webench says unstable @ 3.0V input for 2.8V output?

Mark Hall
Prodigy 140 points
Part Number: TPS552882

Tool/software:

We are trying to use the TPS552882RPMR device with 2.8V/1A output for input range of 3.0V to 25V and Webench is saying the design is unstable.

Also - why is the part spec'd at 2.7V operation, but will not power up at 2.7V? If the UVLP requires 3.0V, then the bullet list should use 3.0V....

We have the design up and running, but we're getting a ~6mA increase in input power consumption @ 3.0V input, with very light load?

  • 0
    TI__Genius 17610 points

    Hi Mark,

    3V to 25V input, 2.8V 1A output case is OK for TPS552882. The UVLO rising is 3V(max) and falling is 2.7V(max), so for your application, it's OK.

    And for your last question, could you explain more? Thanks.

  • 0 in reply to Shipeng Cheng
    Prodigy 140 points

    Why does Webench still say design is unstable for input voltage 3.0V? See screen capture;

    (we take the original Webench design and change ONLY the input from 2.8V to 3.0V)

    As for the increase current consumption - we have previous revision board (with another vendor DCDC) and this revision, with TI DCDC, is consuming 6mA more than previous revision... we are concerned that due to the Webench issue, is the TI design (operating at 3.0V input) inefficient and resulting in the increased power consumption?

  • 0 in reply to Mark Hall
    TI__Genius 17610 points

    Hi Mark,

    Webench is sometimes useless when you type in not typical case. So please ignore this error and just see real bench test result.

    And the 6mA is compared with competitor, so do they share same solution? And what's MODE pin resistor? Recommend to use 24.9k to configure PFM mode, so that the current consuming can be lower at light load.

  • 0 in reply to Shipeng Cheng
    Prodigy 140 points

    Really? I would not have used this part if I had seen the 'unstable' condition from Webench...

    Yes - we had competitor DCDC on previous revision and it's low-load current was 6mA less than this circuit.(with VIN=3.0V and VDD=2.8V)

    We changed to the this TI part because we thought it would START AND run at 2.7V...

    And changing the MODE pin is hard since Webench told me to ground it.... we will try to rework a resistor into the path...

    How will this affect circuit when DCDC is outputting 1A?

  • 0 in reply to Mark Hall
    TI__Genius 17610 points

    Hi Mark,

    Webench is a tool designed and maintained by another team in TI. We cannot control the result in the tool.

    But I need to say that TPS552882 is also start at 3V, 2.7V is shutdown voltage threshold.

  • 0 in reply to Shipeng Cheng
    Prodigy 140 points

    I understand about the SW developers..... the issue is this part should have generated an error with Webench @ 2.7V - I'm betting the SW developers have the same impression as I did... that VIN=2.7V is fine under all conditions...

    And again - on the data sheet, there is NOTHING on the first page that implies it will not START @ 2.7V....  the ONLY way to determine this is by the UVLO line of the table.... there should be text in the description (on first page) saying that 3V is required for the part to start operation.

    Everything on first page implies it will work with an initial 2.7V input.