Hi TI team,
Here is a follow-up of my previous messages regarding output oscillations on LM5069 (https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1311582/lm5069-output-oscillations?tisearch=e2e-sitesearch).
Avishek suggested 3 tests and here are my results.
Proposal-1: Place 10Ω resistance at R1004 and 10nF ceramic capacitor at R1011. Please see the performance.
Result: No effect on oscillations
Proposal-2: Remove this below circuit. Please see the performance.
Result: Oscillations disappear. Instead, EL_LEFT_MES and OUT_SWITCH level decreases a bit. After further tests, Q1000 gate is not stable either but it doesn’t create oscillations thanks to Q1000 body diode.
When removing C1002 and C1003, the power bus is stable (please see oscillograms below).
Proposal-3: Remove Q1000 and connect the OUT_SWITCH net directly to EL_LEFT_MES. Please see the performance.
Result: I didn’t exactly do this test but instead I populated C1003 and removed C1002. Oscillations still appear.
I also tried to add 10R on Q1001 gate (R1007) but it doesn’t help.
Do you have any idea why the soft-start circuit would have this negative effect on the MOSFETs gate?
Thank you,
Best Regards,
Clément
