Other Parts Discussed in Thread: LM358B
My app involves two independent power supplies pulsed alternately ON and OFF (i.e. when one is ON the other is OFF). OFF state is generated by grounding SS. If I have an opamp follower driving COMP pin to Gnd, then COMP pin does go to Gnd with LM5033 in OFF state (i.e. Outputs off). However, if LM5033 is ON then there appears to be an internal (to the IC) active pullup to ~0.73V.
I have not yet closed my feedback loop for the full PS. It is a programmable ~12kV PS and so I am trying to be cautious in bring things up for the first time.
So I have operated only with COMP pin being driven (via LM358B opamp follower) to either ~0V or to ~4.5V so far. These are both well outside of the active duty-cycle adjustment range of ~1.5V to ~3.5V. But when I operate in the ping-pong or see-saw mode described earlier, I do not see PWM at the two push-pull Outputs (i.e. FET gate drivers) only ON with SS at 5V and OFF with SS at 0V. Maybe everything would work as expected if COMP is between 1.5V and 3.5V -- I have not tried this yet, either in an open-loop configuration nor in a closed-loop configuration (i.e. by completing my entire PS circuit).
Can anyone tell me why I am seeing the unexpected behavior with respect to the Outputs and the voltage on the SS pin? I do not see this behavior reflected or explained by anything in the datasheet. Also, the apparent active pullup in the ON state at COMP appears to violate the spec's for short-circuit current on COMP pin (1.5mA max.), since there would have to be > 40mA to overdrive the LM358B opamp output stage, which is what I am observing.
