DRV8143-Q1: Thermal Estimator for PWM Settings

Yuya Shoji

Part Number: DRV8143-Q1

Hi team,

I have a question. How can I calculate thermal under PWM setting? Even if I changed slew rate and duty cycle, the thermal doesn't look changed.

Best Regards,

Shoji

over 2 years ago

0 Jacob Thompson over 2 years ago

TI__Mastermind 23431 points

Hey Shoji,

You're using the Half Bridge Driver Junction Temperature Estimator Excel spreadsheet tool, correct?

It looks like the PWM duty cycle thermals only change if you set the current to a negative value. I'm asking a coworker whether this was on purpose or not, but in the meantime you can run your estimators with a negative current value and desired PWM and it should work for you.

Regards,

Jacob

+1 Jacob Thompson over 2 years ago in reply to Jacob Thompson

TI__Mastermind 23431 points

Hey Shoji,

Yes, this is on purpose. See the HowToUse sheet in the Excel tool for a nice diagram of positive vs negative current and our device. The High-Side FET is assumed to be ON 100% of the time, so the PWM setting doesn't matter for positive current.

Regards,

Jacob

0 Yuya Shoji over 2 years ago in reply to Jacob Thompson

TI__Expert 5680 points

Hi Jacob,

Thank you for checking. Yes I use that. The low side Rds_on is the same as the high sides. So, even when the HS FET is PWM'ed in the real application, we can get the same thermal result by using negative current. Is my understanding correct?

Best Regards,

Shoji

0 Jacob Thompson over 2 years ago in reply to Yuya Shoji

TI__Mastermind 23431 points

Yes, that is correct! It will work out to the same thermal result across all the FETs.

Regards,

Jacob

0 Yuya Shoji over 2 years ago in reply to Jacob Thompson

TI__Expert 5680 points

Hi Jacob,

Understood. Thank you for your support!

Best Regards,

Shoji

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DRV8143-Q1: Thermal Estimator for PWM Settings