PFD delay for eliminating the charge pump dead zone

pfd dead zone

Hi all,

How long is it proper for the delay time? And how to simulate the charge pump dead zone?

Thanks & Best Regards
Analog_starter

.option post=1

Try to simulate the PFD+Charge pump then plot the pahse error (X-axis) Vs. (delta charge; ΔQ of charge pump output (Y-axis)). According to the plot to add the delay until the dead zone is eliminated.

zero deadzone pfd

Hi huanchou,

The question is how I can get the phase error as X-axis? Which simulator do you use? Spectre or Hspice?

Thanks & Best Regards
Analog_starter

the function of delay charge

Hi, I mean the HSPICE simulator.
Try to use the two pulse function as the PFD input.
Let one of the pulse function has the delay parameter say 'delay+phase error'
For example:

V1 in1 ground pulse( HI LO delay rising falling duty period)
V2 in2 ground pulse( HI LO 'delay+phase error' rising falling duty period)

Then run the tran. simulation and sweep the "phase error" this parameter.

charge pump dead zone

Hi huanchou,

Thanks a lot!

Thanks & Best Regards
Analog_starter

Added after 7 minutes:

BTW, which parameter of charge pump stand for the delta charge (Y-axis)? How can get it?

Thanks & Best Regards
Analog_starter

spectre special fuction pfd deadzone

Try to use the LX0() to plot the charge in the cap.
Don't forgot to put the cap in the charge pump output.

what is a pfd pump

Hi huanchou,

I have tried it, but can not get the .tran sweep plot waveform that "LX0(CCtest)" as the Y-axis VS. "p_error" as the X-axis. Could you show me the error?

And I think it should be the ΔQ VS. p_error around the phase error time piont, not the "charge stored in capacitor (LX0)", right? How can you catch the ΔQ value in a transient simulation around the phase error? I am really puzzled by it.

Thanks a lot !!!

My sim file as below:

***module for testing dead zone***
.inc 'PFD_CP.cdl'
.param ups=1.8
.param p_error=14n
.TEMP 25.0000
vdd vdda 0 ups
vss gnda 0 0
vdd2 vdd 0 ups
vss2 gnd 0 0
vsleep sleep 0 0
I_CPN I_CPN 0 -50u
I_CPP I_CPP 0 50u
vref ref 0 pulse ups 0 10n 0.1n 0.1n 25n 50n
vfb fb 0 pulse ups 0 p_error 0.1n 0.1n 25n 50n
************************************************************
.OPTION post=1 PROBE=0 accurate=1
.lib 'XXXX.lib' tt
************************************************************
.tran 0.1n 100n
+sweep p_error 9n 11n 0.1n
.print tran LX0(CCtest)
.end



Thanks & Best Regards
Analog_starter

charge pump deadzone

Can anybody give me some suggestions?

Thanks & Best Regards
Analog_starter

dead zone pfd

just measure the voltage on the capacitance and multiplied by C, that is the Q .
you should add the .meas statemant in hspice list:
.mear tran vcpo avg v(o) from=XXn to=XXn.
.meas charge param='vcpo*C'
where v(o) is the voltage on the capacitance .
the plot is "charge stored in capacitor VS phase error" ,not "ΔQ VS. p_error " you can the value of ΔQ / p_error by measureing the curve.

dead zone pfd

also do a post layout extracted simulation