LMR36006-Q1: Subharmonic effects despite of having chosen a enough big inductor value according to datasheet

Hi,

I tested my design with the eval board LMR33630CRNXEVM.
Since I wanted to test it with the LMR36006AQRNXRQ1, I changed the original controller to this one. Moreover, I changed some capacitors, resistors and the inductor . Changes are reported in the attached file.
I set the output voltage to 16V. With this setup. I got a little, but same change in the dutycycle cycle per cycle (longer-shorter-longer-shorter-...), also known as subharmonic oscillation. I did not expect that because I choose an enough big inductor value to avoid this and the controller implements internal loop compensations. All the details are available in the attached document, with the component designators being referred to the schematic of the eval board LMR33630CRNXEVM.

In the attached file one can see that I got a long-short-long-short pattern, more or less distinctive (see statistics from Oscilloscope).

I tried:

- Reducing the feedback voltage divider impedance from the range 100kOhm to 10kOhm. It improves slightly the difference between the long and the short duty cycle.

- Put different capacitor values in parallel to the upper resistor (feed-forward) as well as the bottom resistor of the feedback voltage divider. It makes it worse.

Does someone have an idea how to get rid of this subharmonic oscillation ? Note that we do not know anything about the internal circuit.

Thanks in advance,

RegardsMeasurements_Results_LMR36006Q1_A_16V.xlsx

Antoine