Your thoughts about drv8316 - Long slew rate

Hi guys,

In recent months and even years now, I’ve had a great expectations from the drv8316. As it has all the good stuff :slight_smile:

  • Integrated triple half bridge
  • integrated low-side current sensing
  • a good LDO
  • relatively respectable current limit 5A/8a peak
  • small package

Recently I’ve had a chance to work with a board with this chip intended to be used with 24V power supply. With this board there was a problem of jerky open loop control of the motor at 25kHz pwm frequency.
Looking at the signals with a scope, I was surprised to see a pretty long rise time of the PWM signal. I was able to measure it at around 1.5us. That is actually very long, I was expecting it to be an order or magnitude smaller from such a recent driver. Going through the datasheet, it seems like this slew rate is actually expected. (datasheet page 63 )

Did some of you guys have similar observations?
Did you see some other limitations of this chip?

Hey, this seems long to me also, but I’ll try to look at one of my DRV8316 drivers under the scope this WE and let you know the results.

I can’t say I remember observing a problem though. The slew rate can be set in a configuration register, and you can set it up to 200V/us, which should give you around 150ns rise time on 24V.

The default setting is 25V/us so it would be around 1us (20-80%) according to the datasheet… that may be the 1.5us you’re seeing if you were looking at 0-100%?

This makes perfect sense, I’ll make sure to try that!

I’was using a relatively low reistance motor, so I’ve had very low voltage in the open-loop, so that might be the issue.

An update to my drv8316 story :smiley:

Setting the slew rate to the maximal value definitely helps a lot. Currents became almost sinusoidal and the torque control now works fine.

Here is the difference using a scope. I’ve changed the slew rate after a few seconds. Two phases out of three are shown in the video.

I am still amazed that there is such a big difference between the slew rates and that the longer one is set by default. With the lower slew rate the PWM is not even center aligned any more.

I was wondering if anyothe have similar issues?
Keep in mind that this issue can be caused by the propriatery board that I’m using too. :smiley:

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