COLIN STEVENSLOW POWER ELECTRONICS
ELEC6270INSTRUCTOR-VISHWANI D. AGRAWAL
Very low voltage 16-bit counter in high leakage static CMOS
technology
Theory and Simulation
.18µm TSMC process in Design Architect Vth NMOS: .3725v / Vth Pmos: -.3948 |Vtp| + Vtn = .7673V
90 ns transient analysis Using ELDO Waveform Viewing in EZWAVE
Counter Selection
Asynchronous Advantages
Simple Design Utilizes Clock Gating Fast for small counters
Disadvantages Ripple Effect Delay Grows with
Counter Size
Synchronous Advantages
No Ripple Effect. Delay of all outputs are equal.
Disadvantages More Logic Required Flip Flops are clocked
even when no transition is required
Results
Voltage Power % Reduction from
Optimal Voltage (1.2V)
Delay (ns)
% Reduction from Optimal
Voltage (1.2V)
5V 5.1264 mW -8482.62% 1.14 71.50%
4V 2.6631 mW -4358.56% 1.19 70.25%
3V 1.1481 mW -1822.15% 1.314 67.15%
2V 0.28895 mW -383.76% 1.89 52.75%
1.4V 90.81 nW -52.03% 3.18 20.50%
1.3V 74.226 nW -24.27% 3.68 8.00%
1.2V 59.73 nW 0.00% 4 0.00%
1.1V 48.232 nW 19.25% 5 -25.00%
1V 39.629 nW 33.65% 7 -75.00%
.9V 33.518 nW 43.88% 9 -125.00%
.77V 25.699 nW 56.97% 17 -325.00%
.76V 25.503 nW 57.30% 19 -375.00%
90ns Transient analysisFrequency
1/(delay + 10%)
(Mhz)
797.45
763.94
691.85
481
285.88
247.04
227.27
181.82
129.87
101.01
53.48
47.85
Sub-threshold Results
Voltage Power (nW) Delay (ns) Frequency
1/(delay + 10%)
0.6 20.60 88 10.33 Mhz
0.5 2.07 477 1.91 Mhz0.4 0.84 3,640 0.25 Mhz
0.3 0.34 30,700 29.61 Khz
0.2 0.20 245,000 3.71 Khz
0.1 0.09 1,880,000 480 Hz
Optimizations and Conclusions
Potential Optimization Low threshold gates could be used along the critical
path of and gates to make the circuit faster at lower voltages.
Conclusions Tradeoff between power and delay for a given circuit. I would like to have gotten the predictive models to
work.
References
Agrawal, V. D. (2007). Power Dissipation in CMOS Circuits [Power Point Presentation]. Retrieved from: http://www.eng.auburn.edu/users/agrawvd/COURSE/E6270_Spr09/LECTURES/lpd_4_CMOSPower.ppt
Counter. (nd) .Retrieved April 15, 2009, from Wikipedia Website: http://en.wikipedia.org/wiki/Counter Low-power electronics. (nd). Retrieved April 15, 2009, from Wikipedia Website:
http://en.wikipedia.org/wiki/Low-power_electronics Kulkarni, Vidya (nd). Logic Design Chapter – 5 [PowerPoint Presentation]. Retrieved from:
forum.vtu.ac.in/~edusat/Prog5/logd/vrk/Chapter-5.ppt