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TPS650250: About three DCDC converter phase

teritama
Expert 2165 points
Part Number: TPS650250

Hi team,

In datasheet p13, it is said "The three DC-DC converters operate synchronized to each other, with the VDCDC1 converter as the master. A 180° phase shift between the VDCDC1 switch turn on and the VDCDC2 and a further 90° shift to the VDCDC3 switch turn on decreases the input RMS current and smaller input capacitors can be used."

In my understanding, this means in PWM mode DCDC1 ~ DCDC3 are switching synchronized 2.25MHz with phase shift said before, but in PFM mode these converter are not synchronized and DCDC1 ~DCDC3 are operated different switching frequency between 1.25MHz and 2.25MHz.

Is this understanding correct?

Best regards,

teritama

  • +1
    TI__Mastermind 21915 points

    Hi teritama,

    That is correct. Once PFM mode (Power Save Mode) is in effect, the switching frequencies and timings are determined by how often the output voltages fall below the Vo threshold, thereby activating the P-channel switch to bring the output back up, not by a set phase shift.

    Regards,

    James