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| DRV8801 OCP Issue |
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| Aleksandar B.:
Greetings everyone, So for a project of mine, I am using TI's DRV 8801 H bridge and found a strange issue with the OCP. The datasheet states that the OCP kicks in when the voltage on the SENSE pin exceeds 500mV, but in my case it kicks in at 100mV. Now the weird part is that the output of the H bridge for current sense is another pin called VPROPI (Voltage proportional to current) which multiplies the voltage from the SENSE pin by 5. I guess this is done to allow for a smaller sense resistor. What bothers me is that the proportion of my error is the same. The OCP kicks in at 5x less than it should. On the other hand, it makes no sense for the VPROPI pin to be saturated at 500mV... The issue exists on all of my boards (around 30 H bridges). I have asked TI's support and they told me to ask my distributor for support because "we (TI) are less technical but sometimes we can help out". So I asked Farnell, who apparently has an "internal link with a team of TI dedicated engineers for technical support", but got no answer. Has anyone encountered similar issues with the OCP on TI devices? Or am I missing something entirely. |
| CM800:
"we (TI) are less technical but sometimes we can help out" That sounds absolutely hysterical, the MANUFACTURER of many advanced semiconductors, designers of the dev / prototype boards etc... are less technical?...... what? Sounds like a case of Lazy. I was actually really looking at some of their microcontrollers... but with that kind of stuff being batted about.... nuh-uh. |
| danadak:
You are conforming to the points made in 9.3.11 and using a .2 ohm (from datasheet, for 500 mV typical trip) ? Regards, Dana. |
| Aleksandar B.:
--- Quote from: danadak on June 20, 2016, 10:49:47 am ---You are conforming to the points made in 9.3.11 and using a .2 ohm (from datasheet, for 500 mV typical trip) ? Regards, Dana. --- End quote --- I am using an 1 Ohm resistor on the sense pin because the current on the motor is not high. |
| bdeianov:
--- Quote from: Aleksandar B. on June 20, 2016, 06:26:34 am ---So for a project of mine, I am using TI's DRV 8801 H bridge and found a strange issue with the OCP. The datasheet states that the OCP kicks in when the voltage on the SENSE pin exceeds 500mV, but in my case it kicks in at 100mV. --- End quote --- Did you ever figure this out? I'm using the DRV8801 for a project and trying to work out the best VPROPI/SENSE setup. 1 Ohm sense resistor sounds about right for my application as well. My current prototype uses a breakout board from Pololu which includes a 0.1 Ohm sense resistor. Not sure why they did that as it makes the VPROPI level unusably low for low powered motors. |
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