supply voltage biasing andy whetzel and elena weinberg university of virginia
TRANSCRIPT
Supply Voltage Biasing
Andy Whetzel and Elena WeinbergUniversity of Virginia
Agenda• Background
o FinFET technology
• Problem and approach• Our design• Implementation• Results• Discussion• Conclusion
BackgroundFinFET Technology• Scalable• Higher drive strength per unit silicon
Image from: http://www.ece.uc.edu/~kroenker/Research/Research%20Project%20Summaries/FINFET_image004.jpg
Image from: http://www.siliconsemiconductor.net/images/news/image-76523-2012-12-12.jpg
ProblemBody biasing does not work on FinFETs• MOSFET vs. FinFET:
https://www.semiwiki.com/forum/content/attachments/5665d1355855218-planar-vs.-3d-finfet.jpg
ApproachSupply voltage biasing with FreePDK
Contributions:1. Our design for supply voltage biasing2. A new knob3. A new technique for decreasing delay in
integrated circuits (ICs) implementing FinFET technology
Supply Biased Inverter Gate
Ring Oscillator
• 11 Inverters• Swept bias voltage
from -0.1 V to 0.1 Vo 1.1 V nominal
• Measured frequency, active power, and static power vs. bias voltage
Ring Oscillator Results
-0.15 -0.1 -0.05 0 0.05 0.1 0.150
2
4
6
8
10
12
Frequency vs. Supply Bias
Bias (V)
Norm
ali
zed F
req.
-0.15 -0.1 -0.05 0 0.05 0.1 0.150
0.5
1
1.5
2
Active Power vs. Supply Bias
Bias (V)
Norm
ali
zed P
ow
er
-0.15 -0.1 -0.05 0 0.05 0.1 0.150
10
20
30
40
50
60
Static Power vs. Supply Bias
Bias (V)
Norm
ali
zed P
ow
er
NAND and NOR Gates• Designed similarly to supply biased inverter
o Double the transistors, one high and one low output
• Setup in ring oscillator configuration such that high output is tied to NMOS and low output is tied to PMOS in subsequent gate
• Results were similar, therefore we obtained the motivation to pursue combinational logic other than a ring oscillator
Full Adder
8 Bit Ripple Carry Adder
-150 -100 -50 0 50 100 1500
0.20.40.60.8
11.21.41.6
Delay vs. Supply bias
Bias (mV)
Norm
ali
zed D
ela
y
-150 -100 -50 0 50 100 1500
10203040506070
Static Power vs. Supply Bias
Bias (mV)
Norm
ali
zed S
tati
c P
ow
er
-150 -100 -50 0 50 100 1500.0
0.5
1.0
1.5
2.0
2.5
Switching Power vs. Supply Bias
Bias (mV)
Norm
ali
zed P
ow
er
-120 -100 -80 -60 -40 -20 00.0
0.2
0.4
0.6
0.8
1.0
1.2
Static Power vs. Reverse Supply Bias
Bias (mV)Norm
ali
zed S
tati
c P
ow
er
Discussion
• Our design shows potential to reduce delay in ICs
Trade-offs:• Area• Power
Conclusion• We successfully designed and implemented a new
knob• Our design decreases delay in ICs implementing
FinFET technology• Area and power trade-offs
Future Work• Further investigation of static and switching power in
FinFETs under supply bias• Explore accuracy of gate induced drain leakage (GIDL)• Generating bias voltages
Questions?
Image from: http://www.synopsys.com/Company/Publications/SynopsysInsight/Pages/Art2-finfet-challenges-ip-IssQ3-12.aspx