I checked Phase Margin (PM) using LTpowerCAD about LTM4637.
I loaded default solution in LTpowerCAD.
When Iout = 20 A, Phase + 180 deg is enough in all frequency.
When Iout = a few A,
Iout = 数Aの場合、PM > 70 deg
However, Phase + 180 deg < 20 deg @ 2.5 kHz.
Is it stable when Iout = a few A ?
If at crossover frequency, PM>45 deg, the loop is stable.
We usually check the phase margin at crossover frequency, for your design, at crossover frequency, the phase margin is larger than 70 degree, then the loop is stable.
You mean it is not necessary to consider about phase @ lower frequency than crossover frequency ?
If so, is it general theory ?
Please tell me why that feedback loop is stable.
Can you post the loop gain and phase together?
I posted the loop gain and phase.
Vin=5 V , Vout = 0.85 V, Iout =5 A
Crossover frequency : fc = 45 kHz.
Even in the case of existing the frequency region that the phase < 45 deg (@ f < fc),
Is the feedback loop stable if PM > 45 deg ?
Thank you for your advise.
I understood that the loop is stable.