Hello,
We’re having an issue with the UC3854B PWM controller. Specifically for the current amplifier section (pins 3, 4, 5), what is the input common mode operational range? The datasheet shows a CMMR Rejection spec. but not an operational limit. What I am seeing is that when the signal that is controlling the I_sense pin goes to zero, the output (CAO) changes behavior.
I have this amplifier set up as a PI compensator with the Zero components at 49.9K ohms and 47nF, and the Pole cap is 10nF. The input resistor to I_sense is 8.45K.
What we see is that when Mout is still at just under 200mV and the current feedback voltage hits zero volts, the output is integrating at a much slower rate as when Mout was 300mV and the current feedback was 100mV. The input difference is the same but the output behavior is different. In the latter case, the integration rate is what I would expect it to be.
Thank you for your help
