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CSD18532KCS: Switching frequency

Part Number: CSD18532KCS
Other Parts Discussed in Thread: DRV8323, , CSD

I am looking at using the DRV8323 with CSD88599 FETs for a motor drive system, operating at 48V/4A nominal.

I see however that in the Recommended operating conditions of the CSD18532KCS FET datasheet, FSW is suggested between 5 and 50kHz. We are keen to use a frequency of 100kHz as we normally would and the DRV 8323 appears to support this with a maximum of 200kHz.

Question:

Is possible to use the CSD 88599 at 100kHz?

What the implications would be, i. e. would a larger boost capacitor be required or would there be a significant loss in efficiency?

Are there any other TI FET's more suitable, based on voltage/current/frequency specs above?

  • Carlos,

    The CSD88599 will operate equally as well as the CSD18532KCS, it is possible to run the CSD88599 @ 100kHz, it simply comes down to powerloss at this higher than normal motor drive frequency.
    Our apps team are on thanksgiving vacation, I will contact them and see if there is a better recommended FET, we will be back to you early next week.

    Chris
  • Hi Chris,

    I would normally calculate switching losses based on rising/falling time, device recovery charge, current and voltage. As such I'm trying to understand the reason for a recommended operating frequency. Surely the device could simply be de-rated (lower current capability) at higher switching frequencies, to maintain powerless constant?

  • Carlos,

    There is no technical reason the CSD88599 had a limit of 50kHz in the datasheet, as you observe the device will simply generate more powerloss and hence lower the output current capability.
    50kHz was simply chosen as we thought this covered the target application of motor control, as it is very unusual to have motors running up at 100kHz where you are wanting to operate.

    Chris...
  • Thank you Chris.

    That's all I need to know. These 'recommendations' often make things a bit more confusing that needed :)