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Spikes on switch 3 during ramp-up - using KITPF8100FRDMEVM

Question asked by Bernhard Fink Employee on Jul 8, 2019
Latest reply on Jul 31, 2019 by Jose Alberto Reyes Morales

Customer:     SICK (Germany)

Platform:       i.MX 8M-Mini + PF8200 (for safety purposes)



I got a question from SICK with regards to the PF8200. They work on the PF8100 FRDM EVM and have seen the following behavior:



During the power up sequence, some switches have voltage spikes during ramp ups. But the buck converter switch 3 (blue curve) has a spike at the regulated voltage as seen from the picture below:



Now this voltage from buck 3 goes to the i.MX 8M-Mini and it would be helpful to know why this happens. This spike does not happen when only switch 3 is ON and rest of the bucks are off.