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TPS548D22: Fsw is set to 650KHz, what is spec tolerance when Vin is 12V and Vo is 3.3V/7A?

Tiger Yeh
Expert 5635 points
Part Number: TPS548D22


Hi,

According to the discussion thread, https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/909206/tps548d22-frequency-curve?tisearch=e2e-sitesearch&keymatch=TPS548D22%25252525252525252520Frequency#, the Fsw will base on input voltage and output voltage.

  Vin = 12 V, Vout = 0.6V, Iout = 5A Vin = 6 V, Vout = 0.6V, Iout = 5A Vin = 12 V, Vout = 1.0V, Iout = 5A Vin = 12V, Vout = 5.5V, Iout = 8A
Set Fsw (kHz) Fsw (kHz) Fsw (kHz) Fsw (kHz) Fsw (kHz)
315 317.7 301.8 314.0 290.4
425 428.8 405.0 428.3 387.8
550 519.1 509.9 545.1 486.9
650 581.7 613.4 658.6 582.6
825 649.9 767.6 806.2 725.4
875     883.8 828.7
1050     977.6 975.6
1125       1166.2

Currently, my customer is measured 574KHz when to set Fsw is 650KH and Vin is 12V, Vo is 3.3V/7A.

Is it normal? What is the spec tolerance when Vin is 12V and Vo is 3.3V/7A?

Thanks and Best regards,

Tiger

  • +1
    TI__Guru 56985 points

     

    The nominal frequency at 3.3V in runs about 10% below the 1V value due to the higher efficiency at 12V to 3.3V compared to 12V to 1.0V.  The tolerance band is about +/- 10% around that.  That gives a frequency range of 525kHz to 650kHz.  Since the switching frequency is accounting for losses, the higher the DCR of the inductor and more losses in distribution to the sensed output voltage, the higher the switching frequency will tend to be.