74actq541scx-nl Fairchild Semiconductor, 74actq541scx-nl Datasheet - Page 6

• Manufacturer Part Number: 74actq541scx-nl
• Description: 74actq541 Quiet Series Octal Buffer/line Driver With 3-state Outputs
• Manufacturer: Fairchild Semiconductor

©1993 Fairchild Semiconductor Corporation
74ACTQ541 Rev. 1.5
FACT Noise Characteristics
The setup of a noise characteristics measurement is
critical to the accuracy and repeatability of the tests. The
following is a brief description of the setup used to
measure the noise characteristics of FACT.
Equipment:
Procedure:
1. Verify Test Fixture Loading: Standard Load 50pF,
2. Deskew the HFS generator so that no two channels
3. Terminate all inputs and outputs to ensure proper
4. Set the HFS generator to toggle all but one output at
5. Set the HFS generator input levels at 0V LOW and 3V
Notes:
8. V
9. Input pulses have the following characteristics:
Hewlett Packard Model 8180A Word Generator
PC-163A Test Fixture
Tektronics Model 7854 Oscilloscope
Figure 1. Quiet Output Noise Voltage Waveforms
reference.
f = 1MHz, t
500Ω.
have greater than 150ps skew between them. This
requires that the oscilloscope be deskewed first. It is
important to deskew the HFS generator channels
before testing. This will ensure that the outputs switch
simultaneously.
loading of the outputs and that the input levels are at
the correct voltage.
a frequency of 1MHz. Greater frequencies will
increase DUT heating and effect the results of the
measurement.
HIGH for ACT devices and 0V LOW and 5V HIGH for
AC devices. Verify levels with an oscilloscope.
OHV
and V
r
OLP
= 3ns, t
are measured with respect to ground
f
= 3 s, skew < 150ps.
6
V
■
■
■
V
■
■
■
■
OLP
ILD
Determine the quiet output pin that demonstrates the
greatest noise levels. The worst case pin will usually
be the furthest from the ground pin. Monitor the output
voltages using a 50Ω coaxial cable plugged into a
standard SMB type connector on the test fixture. Do
not use an active FET probe.
Measure V
the worst case transition for active and enable.
Measure V
the worst case active and enable transition.
Verify that the GND reference recorded on the
oscilloscope has not drifted to ensure the accuracy
and repeatability of the measurements.
Monitor one of the switching outputs using a 50Ω
coaxial cable plugged into a standard SMB type
connector on the test fixture. Do not use an active
FET probe.
First increase the input LOW voltage level, V
the output begins to oscillate or steps out a min of 2ns.
Oscillation is defined as noise on the output LOW
level that exceeds V
that exceed V
which oscillation occurs is defined as V
Next decrease the input HIGH voltage level, V
the output begins to oscillate or steps out a min of 2ns.
Oscillation is defined as noise on the output LOW
level that exceeds V
that exceed V
which oscillation occurs is defined as V
Verify that the GND reference recorded on the
oscilloscope has not drifted to ensure the accuracy
and repeatability on the measurements.
Figure 2. Simultaneous Switching Test Circuit
and V
/V
OLV
IHD
and V
OLP
OHP
:
IH
IH
and V
and V
limits. The input HIGH voltage level at
limits. The input LOW voltage level at
OHP
IL
IL
/V
OLV
OHV
limits, or on output HIGH levels
limits, or on output HIGH levels
OHV
on the quiet output during
on the quiet output during
:
ILD
IHD
www.fairchildsemi.com
.
IL
, until
IH
, until