PROPAGATION DELAYS
INTRODUCTION TO STD80/STDM80
STD80/STDM80
1-10
SEC ASIC
Best and Worst Case Conditions
A circuit should be designed to operate properly within
a given specification level, either commercial or
industrial. It is recommended that circuits be simulated
for best case, normal case, and worst case conditions
at each specification level.
The following expressions also allow for the effect of
process variation on circuit performance.
Best case:
T
BC
= K
PBC
x K
T
x K
V
x T
NOM
= K
BC
x T
NOM
Worst case:
T
WC
= K
PWC
x K
T
x K
V
x T
NOM
= K
WC
x T
NOM
,where
T
BC
= Best case propagation delay
T
WC
= Worst case propagation delay
T
NOM
= Normal propagation delay
(T
J
= 25
o
C, V
DD
= 5V and typical process)
K
PWC
= Worst case process correction factor
K
PBC
= Best case process correction factor
With above equations, we can calculate the multipliers
of K
WC
and K
BC
as follows.
Table 1-2.
Application
STD80 best case delay
Table 1-3.
Application
STD80 worst case delay
Worst case delay
Parameter
V
DD
4.5V
125
o
C
4.75V
115
o
C
Table 1-4.
Application
STDM80 best case delay
Best case delay
Parameter
V
DD
3.6V
–40
o
C
3.6V
0
o
C
Table 1-5.
Application
STDM80 worst case delay
Worst case delay
Parameter
V
DD
2.7V
125
o
C
3.0V
115
o
C
Derating factors of STD80/STDM80
The multipliers can be applied to nominal delay data in
order to estimate the effects of supply voltage,
temperature and process. Nominal data are provided
for conditions of V
DD
= 5V, T
A
= 25
°
C and typical
process.
The derating factors of STD80/STDM80 are as follows.
Table 1-6.
STD80/STDM80 process derating
factor
Process Factor (K
P
)
Table 1-7.
Temp.
(
o
C)
K
T
STD80 temperature derating factor
Table 1-8.
Temp.
(
o
C)
K
T
STDM80 temperature derating factor
Table 1-9.
Voltage (V)
K
V
STD80 voltage derating factor (K
V
)
5.5
5.25
5
0.94
0.97
1.00
Table 1-10.
Voltage (V)
K
V
STDM80 voltage derating factor (K
V
)
3.6
3.3
0.94
1.00
Best case delay
Parameter
T
J
–40
o
C
0
o
C
K
BC
V
DD
5.5V
5.25V
Proc.
Min.
Min.
Industrial
Commercial
0.51
0.56
K
WC
T
J
Proc.
Max.
Max.
Industrial
Commercial
1.77
1.69
K
BC
T
J
Proc.
Min.
Max.
Industrial
Commercial
0.49
0.52
K
WC
T
J
Proc.
Max.
Max.
Industrial
Commercial
1.97
1.77
Slow
1.40
Typ.
1.00
Fast
0.60
125
85
70
25
0
–40
1.21
1.12
1.09
1.00
0.95
0.87
125
85
70
25
0
–40
1.18
1.10
1.08
1.00
0.96
0.90
4.75
1.04
4.5
1.07
3.0
1.08
2.7
1.19