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UCC28220: Lowest switching frequency

David O.
Prodigy 30 points
Part Number: UCC28220

Hello,

I am a bit confused about the lowest PWM switching frequency.

On one side, from the datasheet:

8.3.3 Oscillator Operation and Maximum Duty Cycle Setpoint
The oscillator uses an internal capacitor to generate the time base for both PWM channels. The oscillator is
programmable over a 200-kHz to 2-MHz frequency range with 20% to 80% maximum duty cycle range. Both the
dead time and the frequency of the oscillator are divided by 2 to generate the PWM clock and off-time
information for each of the outputs.

So, I guess the lowest fs (Fout) in the switch is 100kHz.

But, also from the datasheet, I find this graph:

Telling that, using 120k aprox. resistors I can set 50Khz fs (Fout I guess)

So, can I or cannot set 50kHz as switching frequency Fout?

or, what is the minimum Fout I can use?

Regards,

David

  • +1
    TI__Mastermind 33115 points

    David,

    The graph shows the minimum switching frequency of ~50kHz, corresponding to the minimum oscillator frequency of ~100kHz which is the minimum programmable frequency by RCHG, RDSCH. These programming resistors also influence the max duty cycle and SS according to section 8.3.4 of the UCC29220 data sheet.

    Regards,

    Steve M