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The Effects of Pipelining on Signal Accuracy
and Propagation Delay
Ammon Hardcastle
Advisor Dr. Ken Stevens
Overview
► Problem
 Passive circuit noise
 Active circuit noise
► Test
circuit qualifications
► Circuit design
► Simulation setup
► Results
► Conclusion
Passive Circuit Noise
► Passive
circuit elements:
resistors, capacitors and inductors

► Clean
signal
► Resistor
► Resistor,
and capacitor (RC)
capacitor and inductor (RLC)
Active Circuit Noise
► Active
circuit elements:
► Saturation
transistors
current

► Triode
current

► Non-ideal
transistor switching
 Signal integrity
 Signal propagation
Proposed Test
► Design
a pipelined Fibonacci simulator
 Used to test the accuracy of the model order
reductions of the two phase algorithm
►3
desired qualities
 RLC separate from circuit
►Passive
vs. Active noise
 Pipelined
►Signals
can be evaluated throughout the circuit
►Signal locations are known throughout the circuit
 Testable
►Signals
are predictable
Circuit Design
► Fibonacci:
Starting at stage 6 (8 13 21 34...)
► 4 circuit designs:




1 Stage (8  21)
4 Stages (8  89)
8 Stages (8  610)
16 Stages (8  28, 657)
Power In
13
8
16-Bit Adder
16-Bit Register
Micron Single Layer Package
21
89
610
Power Out
28,657
Simulation Setup
► Purpose
of simulations
 Determine accuracy of propagating signals
 Compare differences between simulators
►3
test simulation
 Control
►HSPICE
►Ideal
power  1.2V (No Noise)
 Single voltage source through package
►HSPICE
and HSimPlus
 Independent voltage sources through package
►HSPICE
and HSimPlus
Results
 Independent
Single
Ideal voltage
voltagevoltage
source
source sources
►HSimPlus
HSPICE multiple
single
vs. HSPICE
vs. Single
vs. Ideal
Results - Continued
► Delay
variation from control simulation
575
525
Delay (pS)
475
425
HSPICE Single
375
HSPICE Mult
325
275
225
175
125
75
25
-25
0
2
4
6
8
Stages 10
12
14
16
18
575
525
475
Delay (pS)
425
375
325
HSIM Single
275
225
HSIM Mult
175
125
75
25
-25
0
2
4
6
8
Stages 10
12
14
16
18
Conclusion
► Power
 IC designs sensitive to current fluctuations
► 1st stage has the largest current
 1st stage has largest signal delays
► Mean
variation
delay caused by noise decreases as the signal propagates
 Multiple supplies have little affect on this circuit
► Worst
case improvement of only .5%
► 6 cases with no improvement
► Signal
Propagation
 Golden model underestimates actual delay
► Variations
► HSimPlus
up to 544pS (HSPICE)
vs. HSPICE
 1st stage delay only 50% of HSPICE
► Largely
underestimates noise affects for this circuit