LM5145: cannot handle current above 3A

Hi Tim, thank you for valuable advice. My output ceramics was rated for 25V, and electrolytic for 35V, I changed ceramics to 16 x 10uF/50V, electrolytic to 220uF/63V (cannot find polymer caps locally, will order and wait for delivery), eyeballed derating by dividing total capacitance in half (sorry for that, your excel derating tool amazing, but I haven't values of ESR for this particular caps) and calculated new compensation network values.

Cc1 was 2.7nF, now 2.7nF;

Cc2 was 27pF, now 39pF;

Rc1 was 56.2k, now 39.2k;

Rc2 was 1.5k, now 102R;

Cc3 was 2.7nF, now 1.8nF;

I soldered the closest possible values from what I have, and almost nothing changes.

However, I noticed that converter handles 6A while VIN 44V or lower, 5A up to 48V and 4A up to 55V. Why lower input voltage works better, is it also evidence of wrong compensation, or it's something else? I would appreciate any help with this.

P.S. pwm signal on HO, LO and SW without load after recalculating COMP network began to change width chaotically like on video under load (before it signal width was more stable)

don't know, is it related or not, changed Rt resistor to increase Fsw from 200kHz to 300kHz, just for test. Controller still shuts down while in increasing load from 4A to 5A, BUT if I set 6A and just go on or off load, it withstands it solid. So, maybe noname inductor from LCSC saturates much more earlier, than it should be... is it possible, or it's just coincidence? And if it holds 6A, why it still goes off after 4A?

Hi Timothy, thanks for your advices! Just removed electrolytic, recalculated comp network and went back to Fsw=200kHz. Signals on SW, HO and LO rock-solid from 0 to 4A, but still goes to shutdown while increasing from 4A to 5A. If I set 5A  or 6A on electronic load, and turn it on, converter works, but signals on HO, LO and SW starts wiggling back and forth. So, is it now just a question of precise compensation (like, I needed 68pF, and just used two 33pF in parallel), or it maybe something else?

Also, while it goes to protection mode, signal on SW looks like this:

Final quickstart file:

6786.24v.xlsm

I've played around few parameters:

1. Crossover frequency, converter became more unstable on higher one (30 kHz), so I went down to 20 kHz;

2. increased current limit to Iout*2, by setting Rilim to 1.2kOhm;

3. noted that 1mOhm and 0.1mOhm of output ESR making significant difference in Rc2, so changed it accordingly.

And in the end of the day it worked without any problems, output current rising and falling without shutting down, control signals stable (as for my opinion). So, I think that's it, and I hope it's not an coincidence ;)

So, I want to thank you so much for your valuable debugging advices, especially because now I'm thinking that all of my other synchronous converters may be suffering from similar design mistakes (because of similar symptoms, like unexpected shutdown).

P.S. Is it worth it to switch from CCM to DCM to decrease losses on light loads, or converter will suffer on max output current?