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Design >> Analog Design >> differential delay cell with wide tuning range
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Message started by casual on Jun 27^th, 2010, 8:40pm

Title: differential delay cell with wide tuning range
Post by casual on Jun 27^th, 2010, 8:40pm

I am looking for differential delay cell with wide tuning range. The delay range is from 30/40~60/70ps. Target is 50ps!

I tried to use simple differential cell with pmos active load + replica bias (Maneatis type without diode-connected transistor). I found the range is too small to cater process variation..

thinking for programmable load or mux...
any advice..?
any good high-speed delay cells?

Title: Re: differential delay cell with wide tuning range
Post by Mayank on Jun 27^th, 2010, 9:01pm

Quote:

I tried to use simple differential cell with pmos active load + replica bias (Maneatis type without diode-connected transistor). I found the range is too small to cater process variation..

I feel Maneatis Delay Cell can be tuned over your required range by varying Tail Current Source.
Is the change in swing not acceptable to you ? Otherwise you should have obtained a good tuning range.
You can go for calibrated capacitive loading on oscillator nodes too, if needed.

Title: Re: differential delay cell with wide tuning range
Post by casual on Jun 27^th, 2010, 9:24pm

yes. the amplitude is getting smaller in some range.

I notice there are two types of famous differential delay cell.

1) Maneatis type -->adjusting Vctrl (amplitude), changing I
2) Maneatis type -->adjusting Vbias (current), changing V

which one is better?
The only difference i found is the tuning range. 2) tends to be smaller range but frequently used in DLL

Title: Re: differential delay cell with wide tuning range
Post by raja.cedt on Jun 27^th, 2010, 9:52pm

hi casual,
upto my knowledge Maneatis cell can cover pretty wide range, so if you need more than that better go for calibration what mayank has reported.
by the way what do you mean by '2) Maneatis type -->adjusting Vbias (current), changing V '

Thanks,
Rajasekhar.

Title: Re: differential delay cell with wide tuning range
Post by casual on Jun 27^th, 2010, 10:16pm

Yes. Maneatis delay cell is the most wide range i have ever found.
However the wide range is mostly cover the low freq range.

50ps delay and the input freq is 10Ghz. The amplitude is getting small at high freq.

Code:

what do you mean by '2) Maneatis type -->adjusting Vbias (current), changing V '

Some designs do not use opamp, directly adjust vbias (Vbn) of the current source & replica bias. You could refer to those DLL papers.

Title: Re: differential delay cell with wide tuning range
Post by raja.cedt on Jun 27^th, 2010, 11:27pm

hi casual,
how low you are getting..even i did one DLL for 3.2g in 4 stages which is almost like 80p. There i got roughly 350mv swing, even if you are not getting you can achieve good swing by changing little bit top pmos triode device.

could you please give me any reference
'2) Maneatis type -->adjusting Vbias (current), changing V '
Thanks,
Rajasekhar.

Title: Re: differential delay cell with wide tuning range
Post by casual on Jun 27^th, 2010, 11:49pm

A Wide-Range Delay-Locked Loop With a Fixed Latency of One Clock Cycle

Basically it is similar to maneatis type but it is without opamp. It is suitable for DLL application since DLL reset from max freq to target freq.

I need to cover process variations and i am using old process 0.18um. Pushing to the limit of 10GHz.

I manage to get it but the power consumption is relatively high.