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TPS62148: Want to use PFM Mode (Burst Mode) - Not PWM Mode

Darren (FAE)
Expert 5483 points
Part Number: TPS62148

I need to support a customer design with TPS62148. 12Vin to 5V / 3.3V out, at 400mA max load.

The customer has done the design before with PWM mode, but really needs squeeze the highest performance possible out of the device for best efficiency, so is considering running in PFM mode. 

Figure 30 / 32 from the datasheet show the output voltage varies with load in PFM mode. That is, for a FB setting, the output voltage varies with current. I need to provide some information on the FB setting vs output voltage for a given load. Do we have any data to support this? The graph seems to suggest the FB voltage setting is highly dependent upon load.

Since the output voltage varies with load, then what is the proper design procedure to make sure that during rapid load changes the output voltage stays within designed limits...?

You can message me offline or we can setup a call if the answer is too complex for E2E.

Regards,

Darren

  • 0
    TI__Intellectual 1610 points

    Darren,

    I believe your best option here would be to model the customer design in PSpice for TI as the amount of output voltage ripple in PFM mode will end up determining the final DC output voltage value.  And, the PFM output voltage ripple will not only vary with the load, but the input/output voltage combinations, as well as the inductor and output capacitor values are all going to significantly impact how much ripple there will be.

    Sincerely,

    -Matt