LDO design --- zero (compensation) dependency on Cout

[taofeng]

Hi ,
I am desiging a LDO. And the Cout will be in a wide range from 100pF to 100nF. I am wondering how to do the compensation.
I would say it is better to make the dominant pole inside. However, the big issue comes when the load current is small and the Cout is large. So, I decide to use pole zero compensation. That is to say I internally generate an zero which will compensate the output pole in a wide current and Cout range.
The dependency of zero on the load current is relatively easy if you image just a current mirror. the problem now is to figure a circuit to track the change of the Cout. I completely run out of idea !
hope someone can help me out.

regards,

jeffrey

 

[robicyang]

use pole-zero tracking compensation and nest miller compensation

related paper:

K. C. Kwok and P. K. T. Mok
Pole-Zero Tracking Frequency Compensation for Low Dropout Regulator
IEEE InternationalSymposium on Circuits and Systems
vol. 4, pp. 735-738, May 2002.

K. N. Leung, P. K. T. Mok, and W. H. Ki
A Novel Frequency Compensation Technique for Low-Voltage Low-Dropout
Regulator
IEEE International Symposium on Circuits and Systems
vol. 5, pp.102-105, May 1999.

Added after 9 minutes:

possible useful paper for you