Hi,
My question as below:
1. The D-CAP+TM Bode Plots Measurement Setup
What is the correct amplitude and point of signal injection for TPS53688?
2. What is the reasonable gain margin for D-CAP+ TM control system?
Based on TI technical document paper "Slup 173", it recommend the gain margin value as -6 dB to -12 dB.
But for the D-Cap+ TM control system, when we try to improve the transient response the gain margin normally around -3 dB to -6 dB.
Then we do need to sacrifice the transient response for -10 dB gain margin.
But customer is not happy with it.
Therefore we do need TI help to explain it.
BTW, I saw another TI technical document paper https://e2e.ti.com/blogs_/b/powerhouse/posts/the-d-cap-modulator-evaluating-the-small-signal-robustness
Base on it's figure 1,2 & 3, (Bode Plots Curve) which gain margin is less than -10 dB.
Based to my understanding of -10 dB gain margin is to ensure that power supplies produced in large quantities will all be stable, and rsubain that way throughout their lifetime.
This allows parameter changes which could cause the loop gain to change by a factor of approximately 3 before the system becomes unstable.
But as TPS53688 it is digital control and without a lots of R and C device for loop gain compensation.
Therefore, my question is for D-cap + TM what is the reasonable gain margin value is?
