Hi,
I am using AM26LS32ACN IC to interface an encoder signal and pass it to a counter.
The motion section of the board works fine, which means that the IC is working perfectly.
However, in another section of the board I am communicating with an ADC IC using SPI protocol. I realized that AM26LS32 is making noise and due to that SPI communication is interrupting.
When I remove the AM26LS32 everything is working fine but with that installed on the board the noise on power line is awful. I tested the power line of the board (3.3V in my case) with an oscilloscope and it is about 1V!!!!!!
One strange behavior if the IC is that sometimes the noise dies out, which makes the SPI work fine.
I attached a 0.1uF capacitor between pins 8 and 16, but it did not solve the problem.
One observation that I cannot find an explanation is that I turn on the power supply and connect a capacitor with the same polarity (positive to pin 16 and negative to pin 8) the noise exists. Then (with the power still on) I change the polarity (interchange the capacitor's and IC pins) and suddenly the noise goes away. The capacitor is a tantalium 100UF 16V.
Below I have attache a schematic portion of the board related to AM26LS32.