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TPS61099: TPS61099

Ian Wang
Mastermind 28465 points
Part Number: TPS61099

Dear Sir,

We have a question about TPS61099YFFR (or TPS61099YFFT) and found some of the boost converters have higher output voltage.

R1 and R2 set to 909k and 226k ohm with 1% tolerance.

To calculate the output voltage, I suppose we operate in PWM mode, the maximum output voltage should be

1.02 * (909*1.01) / (226*0.99) + 1.02 = 5.205V, but we measure around 5.22~5.24V for some unit.

After checking R1 and R2 at our side, we find they’re in the spec. of 1% tolerance but the output reference voltage is around 1.05V which is higher than we expect.

One thing can explain my measurement result is that we’re perform in PFM mode. If this is true, could you help answer following two questions?

  1. Does we provide all PFM mode TPS61099? Or this is a quasi-mode which decide by the load?
  2. What’s the upper and lower bound of reference voltage under PFM mode?

Thanks, Ian.

  • 0
    TI__Intellectual 2270 points

    1. it automatically transit from PFM to PWM according to load

    2. about PFM Vref spec, from out statistics data, low boundary is ~1.2% high boundary is ~4.1%.

    when in very light load, TPS61099 will be in ultra low power mode which will become pulse skip(different from TPS61099's PFM here, which is one pulse PFM). in this mode, even there will also some delay to response which will increase the output voltage a little.

    Is this voltage very critical? what's the application details. 

  • 0 in reply to Charles Wong1
    TI__Mastermind 28465 points
    From your info. I can summarize that we will have the range of Vref. from 1.017 V to 1.072V at PFM, right?
  • 0 in reply to Ian Wang
    TI__Intellectual 2270 points

    no it's 1.012V to 1.041V.

    so could you post the FB waveform(1V offset), so that we can check whether it's real 1.05V or not.