The motor current acquisition port AN0_0 affected by glitches caused by the PWM pulse of the CP, res

[yq1]

hello

I have encountered a problem. The motor current acquisition port AN0_0 coupled the rising edge and falling edge of CP signal, causing noise. When AN0_0 triggered current collection through PTU, burrs might be collected, which led to inaccurate current collection. Can you give me some advice on this problem? Thank you!

At present, the CP signal frequency here is 20KHz, and the motor drive frequency is 20KHz. The current collection method is: PTU is triggered by PWM rising edge, and then it passes through a fixed time base and triggers ADC collection. The following are the waveforms of AN0_0 and CP.

[yq1 · Accepted solution]

I found the cause:
The test points of the two signal lines at the input of the current acquisition op-amp were placed directly above the CP signal line, resulting in coupled noise, and the output signal of the current acquisition op-amp was free of these two interfering noises when the two test points were disconnected.

[danielmartynek]

Hi @yq1,

Do you use the optional filters at CP / VBS?

AN5207 Hardware Design Guidelines for S12ZVM Microcontrollers:

Regards,

Daniel

[yq1]

Hi Daniel

The design includes the filtering of these two parts. I try to enable CP, then remove the components behind CP and let CP foot hang in the air. At this time, the waveform of AN0_0 port still has the burr of CP coupling, is it possible to coupling through MCU?
I also want to ask whether the software can realize the synchronization of the rising edge of CP and the rising edge of HGx signal, because the frequency of both is 20KHz, so that the effect of CP burr can be effectively avoided after the delay time base is set on the PTU trigger.

thanks 

[danielmartynek]

Why did you choose 20kHz for the charge pump?

The freq. of the charge pump can be change.

Regards,

Daniel