I have some question about this bandgap, which is reference from "A Supply-Noise-Insensitive CMOS PLL With a Voltage Regulator Using DC-DC Capacitive Convertor" by Chang-Hyeon Lee,..
In this paper, no detail description about how it works, and only mention RC filter to filte supply noise, and simple start up.
my question is: What is the role of M1, M2, and M13? Can somebody help me to solve it?
This is self-biased bandgap structure (M13). M13 is providing all the bias currents for the bandgap. Thus, even without M1 and M2, it will work with pretty decent PSRR. However, it may not be very safe design without M2 (M1 is just giving more gain.). If M13 doesn't provide the exact amount of bias current for the bandgap, this circuit will collapse but with M2, this will be prevented.
"The RC passive filter comprised of the Rf1-Rf4 and C1-C4 filter attenuate supply noise at frequencies larger than the response capability of the bandgap reference circuit."
I want to know how to determine the parameters Rf1-Rf4 and C1-C4?
How to simulate this RC passive filter?
Which parameters should be cared?
How much should the -3dB frequency of the RC passive filter?
I strongly agree with your opinion, but the DC voltage on gate of M2 would influence the reject performance; to let the M2 always working in active region when in normal operation at different corner situation is a challenge.
M1 M2 ,i think, provides (with the help of Capacitor) a load which improves PSRR.
M17 as i see is switching ON the current mirror with the help of startup ckt..
M13 (1st ckt.) necessarily provides current to the ckt.
Khong-Meng Tham and Krishnaswamy Nagaraj "A Low Supply Voltage High PSRR Voltage Reference in CMOS Process" IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 30, NO. 5, MAY 1995
I think in this design to have good PSRR, the Vrsup need to be regulated. That mean the M13 transistor must supply more current than it required by the bandgap circuit (M7, M8, M9 branches). M3, M5 and M4 is the bias circuit for M2. The M2 and M1 is used to regulated the Vrsup by sinking the excess current that is not required by the bandgap block. M1 is the gain stage for the regulated Vrsup loop. So it needs to be compensated by C2 using miller compensation.
So, it is important that the M13 transistor supplies more than bandgap block and the bias circuit so that M1 can be used to provided the control to regulated the Vrsup.