Problems with "Fault Glitch Stretch Enable"

[jan1]

Hi there

I am using the MC56F82748 DSC for a PM motor controller.

In this relation I have tried to apply HW filtering of a Fault input. More specifically, I try to apply the "Fault Glitch Stretch Enable" functionality in the register PWMA_FFILTn, however it does not seem to work.

Shortly described, my problem is that no matter, how many samples I apply or which sample rate, the delay applied by the DSC between a signal at the input and PWM inhibit does not change and stays close to zero. It seems like, a change in input voltage bypasses the filter and inhibits the PWM right away, regardless of the delay defined in the register.

Does anyone have experience using the glitch filter?

[xiangjun_rong]

Hi, Jan,

As you know, the PWM_FAULTx signal is very sensitive to noise, in order to avoid the scenario  that the noise disable PWM signals unexpectedly, we design the filtering function of the fault pins.

If you do want to test the delay of the fault filter pin, pls note that the fault filter function uses IPBus clock, I suggest you set the PRSC bits in PWMA_SMnCTRL as 0 so that the IPBus clock can also drive the PWMA_SMnCNT. set the PWMA_SMnVAL1 as 10 or less so that the PWM frequency is high. then you can compare the delay between fault signal and disabled PWM signal.

Hope it can help you.