TIM1_BKIN noise immunity problem

[MMeva.1]

Hello,

I am using STM32VLDISCOVERY board. We have configured TIM1 in PWM mode with break feature enabled. But the BKIN input seems really sensitive and catches noise from the system resulting in a trip. Is there any data that says how much voltage on TIM1_BKIN pin (configured active low) will result in a fault detection ? Or is it the same ViL level as any other GPIO ?

Currently we have the pin configured as input_floating and externally pulled up to Vcc. We suspect that this external trace connectin BKIN and Vcc can catch up noise. If I configure the pin as internal pullup, will it still function as TIM1_BKIN ?

Thanks

[waclawek.jan]

> Or is it the same ViL level as any other GPIO ?

Yes. Would this pin have different input level, it would be mentioned in the Datasheet.

> If I configure the pin as internal pullup, will it still function as TIM1_BKIN ?

Yes, but the internal pullup is relatively weak, nominally 40kOhm.

JW

[Piranha]

Also even if one is using an external pull-up/down, turning on the internal parallel one will add additional noise immunity for a path from the external one to the internal one, which is located in a chip itself.