©1990 Fairchild Semiconductor Corporation

www.fairchildsemi.com

74ACQ573, 74ACTQ573 Rev. 1.5

8

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:

Hewlett Packard Model 8180A Word Generator

PC-163A Test Fixture

Tektronics Model 7854 Oscilloscope

Procedure:

1. Verify Test Fixture Loading: Standard Load 50pF,

500

Ω.

2. Deskew the HFS generator so that no two channels

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.

3. Terminate all inputs and outputs to ensure proper

loading of the outputs and that the input levels are the

correct voltage.

4. Set the HFS generator to toggle all but one output at

a frequency of 1MHz. Greater frequencies will

increase DUT heating and affect the results of the

measurement.

5. Set the HFS generator input levels at 0V LOW and

3V HIGH for ACT devices and 0V LOW and 5V HIGH

for AC devices. Verify levels with an oscilloscope.

Notes:

reference.

17. Input pulses have the following characteristics:

f

Figure 1. Quiet Output Noise Voltage Waveforms

greatest noise levels. The worst case pin will usually

be the furthest from the ground pin. Monitor the output

voltages using a 50

Ω coaxial cable plugged into a

standard SMB type connector on the test fixture. Do

not use an active FET probe.

the worst case transition for active and enable.

the worst case active and enable transition.

oscilloscope has not drifted to ensure the accuracy

and repeatability of the measurements.

Ω

coaxial cable plugged into a standard SMB type

connector on the test fixture. Do not use an active

FET probe.

the output begins to oscillate or steps out a min of 2ns.

Oscillation is defined as noise on the output LOW

the output begins to oscillate or steps out a min of 2ns.

Oscillation is defined as noise on the output LOW

oscilloscope has not drifted to ensure the accuracy

and repeatability of the measurements.

Figure 2. Simultaneous Switching Test Circuit