I am working with an SMC02B chip and sourcing 5V at 20 mA to the Serial Control Input. I have a copy of the User’s Guide, but it does not say what the required input current is. When I connect my source to the Serial Control Input the measurable voltage on the line drops to 1V. I want to know if I don’t have enough current or my motor controller has been fried somewhere along the way.
The chip is just a PIC12F629, so you can check its datasheet for all the I/O pin details. It should not require anywhere near 20 mA since it’s a high-impedance input, so something is definitely wrong in your setup. What voltage are you running everything at, and what are your signal voltage levels? Can you post a picture of your setup?
You are correct something was wrong with SMC02B. I replaced it in my application and am seeing the correct signaling levels.