Author Topic: SC050 Output PWM unstable  (Read 656 times)

Offline Scott_MARL

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SC050 Output PWM unstable
« on: July 03, 2024, 07:56:18 PM »
I have two PWM signals leaving the MFOut of a SC050 controller
Duty out = 6000 - 10000
Safety fet = disabled
Monitoring = disabled
Req Freq = 1000
Output mode = 3 & 6 (tried both)

Typically I would get a smooth voltage that I would read on the input pins, C1p10 & 11 in this case.
The output I am measuring is quite nosy, my C1p02 voltage is steady 11975mV from a filtered power supply.
C1p10 is measuring between 6V and 8.5 volts with a 8hz period (125 ms)



I isolated the circuit so it is a 6 inch wire going from C1p39 to C1p10(scaled to correct range in a pull down configuration).

Troubleshooting with my oscilloscope shows the noise is coming from the output pin C1p39 shows
This is full range PWM (0-12V), which up close looks alright but the leading edge is overshooting significantly and has a very consistent resonance when looking at larger scale. 


For now I can filter this out but I have never seen this before and it is happening to all of my SC050 controllers in our inventory I have tested.
Anyone else see this before?

This is the same circuit sampled from an MC050:


Edit:
After some playing around with settings on the SC050 controller I found using a PWM frequency of 20,000 Hz cleans up the signal significantly.
SC050 with the same settings as above except for PWM rate. This seems logical, just odd that we have not seen this before:




« Last Edit: July 03, 2024, 10:12:11 PM by Scott_MARL »
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