Datasheet

7–157
Slew Rate
Slew rate plays an important role in backplane or point-to-point application designs. The slower the output slew rate of a device,
the less susceptible the signal is to reflections and noise. Based on this data, a designer knows how to terminate a bus or
backplane. Using the characterization laboratory boards, the output slew rate (t
rise
and t
fall
) was taken with and without the
standard output load. Figures 27 and 28 show the output rise and fall times of each output taken between 10% and 90% for
TTL, 0.5 V and 1 V for GTL, and 1.3 V and 1.8 V for BTL. Figures 29 and 30 show the rise and fall time as the number of
outputs switching increases. The curves in both plots look almost flat between one output switching and all outputs switching.
Data is based on the input signal characteristics: V
IL
= 0 V, V
IH
= 3 V, t
r
/t
f
= 2 ns.
Fall Time
3.3-V and 5-V Families
Rise Time – ns
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
T
A
= 25°C,
V
CC
= 5 V (5-V families),
V
CC
= 3.3 V (3.3-V families),
V
IH
= 3 V,
V
IL
= 0 V,
All unused inputs are biased low,
No load
Rise Time
3.3-V and 5-V Families
3.3-V Families 5-V Families
3.3-V Families 5-V Families
Fall Time – ns
LV LVC LVT LVT2 ALVC ABT ABT2 ABTE GTL FB CBT
LV LVC LVT LVT2 ALVC ABT ABT2 ABTE GTL FB CBT
0.2
0
2.4
2.2
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
T
A
= 25°C,
V
CC
= 5 V (5-V families),
V
CC
= 3.3 V (3.3-V families),
V
IH
= 3 V,
V
IL
= 0 V,
All unused inputs are biased low,
no load
Figure 27. Typical Output Rise and Fall Time Measured Between Specified Levels or Voltages