Hello,
We are working with the TL2845 and are wondering about error amplifier sourcing 0.5mA. If we were to disable the error amplifier by grounding the inverting pin, does this mean that the worse-case instantaneous current that we need to pull from the COMP pin to reduce the converter current peak reference to 0 is 0.5mA_min (0.8mA_typical)? We would like to understand how to calculate the optocoupler collector bias current and take worse-case opto CTR into account (opto collector connected to the COMP pin, not shown in the picture).
When the TL2845 error amplifier is disabled (inverting pin connected to ground), what is the small-signal impedance looking into the COMP pin? For small-signal analysis, this impedance is in parallel with the optocoupler collector pullup resistor. Other application notes and webinars talk about the optocoupler output capacitance and the pullup collector resistor (to calculate the pole) but nobody takes into account the small-signal impedance looking into the COMP pin. Or is it so high that can be neglected?
Thank you, Keith
