1
Silicon Odometer: An On-Chip Reliability Monitor for Measuring Frequency Degradation
of Digital Circuits
NBTI impact mitigation techniques• Guard-banding
• Size up devices • Toggle circuit nodes
• Lower temperature
• Vtp and Vdd tuning
NBTI impact on digital circuits• Fmax
• Leakage current
• SRAM cell stability
• SRAM read/write margin
Bottom line: Need to accurately measure the NBTI effect and develop compact models
2
Silicon Odometer
Phase Comp.
Stressed ROSC (freq=fstress)
...
...
Reference ROSC
A
BC
PC_OUT
Measurement
Stress period
VDD_NOM
VDD_STR
0V
(freq=fref)
(freq=fref - fstress)
0
20
40
60
80
100
120
0 0.5 1 1.5 2Frequency degradation (%)
Co
un
ter
ou
tpu
t (N
)
99 98
50
33ProposedConventional
ΔN=1 @ 1%
N=50 @ 1%Δ
• Two free running ROSCs for beat frequency detection
• Count PC_OUT to determine frequency degradation
• Insensitive to environmental variations
• High delay sensing resolution
• Fully implemented by digital circuits
Labview GUI
3
Summary Measurement work bench
0.00%
0.05%
0.10%
0.15%
0.20%
0.25%
0.30%
0 2000 4000 6000Time (sec)
Fre
qu
enc
y d
egra
dat
ion
Vstress=V0, 30C
• Fully digital, minimal calibration
• Sub-picosecond sensing resolution (<0.02% or <0.8ps)
• Microsecond measurement time for minimal recovery (2us)
• Applicable as a on-chip reliability monitor