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sinara-hw / Stabilizer

2-channel microcontroller servo with EEM and Ethernet based on STM32 CPU
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DI0/1 jitter, pulldown #91

Closed jordens closed 2 years ago

jordens commented 3 years ago

I would like to use DI0/1 for accurate and low-jitter timestamping and limiting. Currently it's a plain digital buffer driven from 3V3 digital and limited by the stability of that power supply, without hysteresis, requiring 1V/10ns slew rate.

Maybe we can give it a better supply/threshold and consider a 1V-threshold Schmitt trigger. And we should add a pull-down.

I don't think this should become a zero-crossing detector. That wold make it useless for digital inputs.

gkasprow commented 2 years ago

@jordens what about such a circuit? I added TVS protection, output buffer that can be disabled, Schmitt input. obraz

gkasprow commented 2 years ago

I don't know if LVC14 is precise enough. We can use fast comparators like ADCMP600 or something cheaper

gkasprow commented 2 years ago

LVC14 has 0.6/0.9V thresholds

jordens commented 2 years ago

That circuit looks fine to me. Should the Tvs be after or before the 51R?

gkasprow commented 2 years ago

TVS absorbs the energy. It gives a chance to the next chip to survive. 51R is to reduce the current in case ESD was really high.