I'm a student. Now, I am learning to use LM5030 IC to design a Push-Pull converter. So, I read LM5030's datasheet and can not understand the function of COMP pin (Pin 3). The red line is Feedback circuit, input its connect to VOUT, output its connect to COMP pin. enter image description here Following the info in the datasheet, it's said: " The comparator polarity is such that 0 V on the COMP pin will cause a zero duty cycle". The duty cycle is to switch on/of 2 MOSFET. And in above figure, the output of the feedback circuit will make COMP = 0 when VOUT > 0, it means the duty cycle for 2 MOSFET will be zero.
That makes me can not understand. Did I miss something?

P.S: LM5030 datasheet

  • $\begingroup$ Is VOUT same as VCC in the diagram? $\endgroup$ Dec 6, 2019 at 16:29
  • $\begingroup$ Yes. I edited it. $\endgroup$ Dec 7, 2019 at 1:35
  • $\begingroup$ There are two COMP in the above circuit. Pin 3 of LM5030 and Pin 4 on LM3411. Pin 3 of LM5030 is an input/output pin. Can you please clarify this in your questions? $\endgroup$ Dec 7, 2019 at 12:39
  • $\begingroup$ My question is on Pin 3(COMP) of LM5030 as I mentioned on the title. $\endgroup$ Dec 11, 2019 at 1:23

1 Answer 1


As indicated in LM5030 datasheet COMP is output to an error amplifier.

The circuit for the LM3411 is as follows

enter image description here

The COMP output from the LM5030 is an input to the LM3411 which is an precision secondary regulator.

The LM3411 is a low-power fixed-voltage (3.3 V or 5 V) precision shunt regulator designed specifically for driving an optoisolator to provide feedback isolation in a switching regulator.

  • $\begingroup$ Thank you. But the point is: VCC = 3.3V => V at pin 1 of U2 = 3.3V (5V) = > Vcomp of LM5030 = 0. When Vcomp = 0V, duty cycle for 2 MOSFET will 0%. $\endgroup$ Dec 5, 2019 at 13:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.