In our module both outputs are generated 28V and 5V output. ADP1074WARWZ-R7 is for 5V generation.
1) In ADP1074WARWZ-R7, 5V output is tested and validated with 28V section disabled. While enabled both section and testing, we have observed no output at no load and loaded conditions. While we probe both 5V and 28V outputs together, the 5V output came and switching happens.
2) We have analyzed and changed the Ccomp capacitor at initially for this issue. We have initial compensation components . Rc - 24.9k, Cc- 47nF , Chf - 100pF. From this , we changed the Cc capacitor to 4.7nF. We observed SR1 and SR2 is not generated and mosfet conduction is happening through body diode and it is visible through switch node waveform and primary gate pulse is also oscillating and not in steady state form. Input current is also consumed more.
3) Then, we changed the compensation according the calculation done once again. Rc- 825ohm, Cc - 22nF, Chf - 1500pF. After changing this combination, we observed some similar issue. SR1 and SR2 pulse are generated but it is in steady state only when we are probing the 5V output along with that otherwise it is oscillating and along with that the primary gate pulse is also oscillating and not in steady state form. Input current is also consumed more.
