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TPS274C65: Datasheet clarification on PWM frequency

Part Number: TPS274C65

Tool/software:

See Figure 9-2. Datasheet calls out 250kHz PWM signal - but I thought HSS were limited to only a few kHz. 

Can you confirm if this is typo in datasheet? I assume author meant 250Hz instead of 250kHz. 

Thanks.

Tyler

  • Update on this one?

    Thanks,

    Tyler

  • Tyler,

    Good question- and yes, this is a misprint. High-side switches in general top out at around 2Khz switching frequency (with some exceptions). Generally the two things that limit PWM frequency are:

    • Slew rate of the device - If the PWM (both through frequency and duty cycle) is switching faster  than the device is able to turn on and off then the resulting output waveform would not be able to keep up with the PWM switching frequency 
    • Switching losses resulting in thermal performance - When the device switches on and off, the device heats up. If you switch too fast, the device will heat and and possibly go into thermal fault.

    We have a good application note that goes into the details of PWMing high-side switches at https://www.ti.com/lit/pdf/slvaf10

    One thing to note is that in applications where the PWM frequency/duty are too high for the high-side switch, it is common to use a low-side switch for the high-frequency switching and a high-side switch for the protection features such as:

    Best Regards,
    Tim