Datasheet

7–165
Skew
Skew is a term that is used to define the difference in time between two different signal edges. There are several different types
of skew currently being used; however, the skew discussed here is the skew of propagation delays across the outputs of a device.
More specifically, it is the difference between the largest value obtained for a propagation delay and the smallest value across
all of the outputs. For example, if output 3 has the largest propagation delay (t
PLH
) and output 14 has the smallest, the output
skew for this device would be the difference between the propagation delays for output 3 and output 14 (see Figure 34).
•
•
•
t
PLH14
t
PLH3
1
2
3
16
Figure 34. Skew = |t
PLH3
– t
PLH4
|
The data presented in this report is taken from devices that have one output switching at a time (V
CC
= MIN and T
A
= 85°C).
This data represents the average worst-case condition skew. Figure 35 shows the skew of the different families using the
standard load specified in data sheets.
Skew – ns
Skew Data
3.3-V Families and 5-V Families
3.3-V Families 5-V Families
LV LVC LVT LVT2 ALVC ABT ABT2 ABTE GTL FB CBT
†
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
T
A
= 85°C,
V
CC
= 4.5 V (5-V families),
V
CC
= 3 V (3.3-V families),
V
IH
= 3 V,
V
IL
= 0 V,
Standard load
†
Data is based on the input signal characteristics: V
IL
= 0 V, V
IH
= 3 V, t
r
/t
f
= 2 ns.
Figure 35. Typical Skew Between Outputs