relation between rise time/fall time and slew rate of pwm waveform

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Hi,
I am using DRV8873 for DC motor control.

In PWM mode, Slew rate table is given as below:

Can anyone pls help how to configure the SR bits in DRV8873 to develop this requirement?

Thanks in advance

 

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Last Edited: Tue. May 19, 2020 - 04:40 PM
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How many volts/us do you need?  Do a calculation & pick the setting that is closest.

Each pulse of the PWM is the slew rate of the pulses, not the overall rampup of the duty cycle (for example, you could take an hour to ramp up duty cycle)

What exactly is your question? Do you have trouble sending in the bits?

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

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That data sheet is using the wrong nomenclature.

 

Rise time is the time taken for a step signal to climb from 10% to 90% of its final value. It is related to the bandwidth of a linear system. Too many years ago now I remember claiming the fastest scope in the lab for my workbench. It proudly displayed 3nS on the front panel. (100MHz).

 

Slew rate is a non-linear effect measured in volts per microsecond, caused primarily by limited current available to charge/discharge fixed or parasitic capacitances.

 

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Slew rate is a non-linear effect measured in volts per microsecond, caused primarily by limited current available to charge/discharge fixed or parasitic capacitances.

good call, sometimes the term slew rate limited, is used to make a further distinction... risetime has units of time, slew rate has units of volts/time  slew rate is a common opamp spec (to the extent it can be nailed down).

 

https://www.edn.com/slew-rate-and-rise-time-not-quite-the-same/  

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Mon. May 18, 2020 - 09:09 PM
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Do you have trouble sending in the bits?

Yes, I have configured SPI module sercom3 of ATSAMD21G17D.

But not sure how to configure registers of DRV8873 using SPI.

Please help me with your inputs.

Thanks in Advance!

 

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But not sure how to configure registers of DRV8873 using SPI.

Well then you are talking about the entire chip functionality, not slew rate!

Have you looked at SPI examples? 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!