DRV8874: current sampling

Annie Liu

Part Number: DRV8874
Other Parts Discussed in Thread: DRV8701,

Hi Team,

Q1: Customer used DRV8874. The actual current of the motor is only 60mA, but the read current is 120mA. May I ask what causes it? The same current read by DRV8701 is correct, AIPROPI (μA/A)=450.

Q2: When sleep is low, the customer uses an oscilloscope to measure OUT1 and OUT2, and there is a 50HZ 12V waveform output directly. May I ask why this happens?

Best regards,

Annie

over 1 year ago

0 Akshay Rajeev Menon over 1 year ago

TI__Genius 17406 points

Hey Annie,

Thank you for your question.

1)Can you provide waveforms of the Output current, and Vipropi?

2) Can you provide waveforms of the nsleep and out1 and out 2?

Best,

Akshay

0 Annie Liu over 1 year ago in reply to Akshay Rajeev Menon

TI__Genius 10295 points

Hi Akshay,

1) The output current uses the data read by the ADC of the microcontroller.

2) nsleep is low level, OUT1 and OUT2 are output square waves with a 50Hz duty cycle of 50%.

And as a comparison, the current detection of DRV8701 is very accurate. Customer wants to know what is the situation?

Regards,

Annie

0 Annie Liu over 1 year ago in reply to Annie Liu

TI__Genius 10295 points

The customer refers to the similar problem about current inaccuracy in this thread, but the problem is not solved.

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1062391/drv8874-q1-the-current-output-pin-ipropi-conversions-to-the-motor-current-and-the-measured-results-are-quite-different-from-the-conversion-result

0 Akshay Rajeev Menon over 1 year ago in reply to Annie Liu

TI__Genius 17406 points

Hey Annie,

1)I want to see the Vipropi voltage to see how what current is being shown before making conclusions. It is possible that the error is being shown due to the very small current leading to noise which is why your ADC thinks 120 mA is being passed. The Vipropi would be very small which could be leading to the error.

If that is the case then increasing the Ripropi to in turn increasing the Vipropi might work. But note that changing Rporpi will also result in different Itrip.

2) I would like to see a waveform of the nsleep and outputs to know what is happening.

Best,
Akshay

0 Akshay Rajeev Menon over 1 year ago in reply to Akshay Rajeev Menon

TI__Genius 17406 points

Hey Annie,

In the mean time, I recommend reading through this Ipropi FAQ for more information.

https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum/1013146/faq-how-to-configure-ipropi-and-current-sensing

Best,

Akshay

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DRV8874: current sampling