© 2006 Fairchild Semiconductor Corporation

www.fairchildsemi.com

FMS6502 Rev. 1.0.0

10

Crosstalk

Crosstalk is an important consideration when using the

FMS6502. Input and output crosstalk represent the two

major coupling modes that may be present in a typical

application. Input crosstalk is crosstalk in the input pins

and switches when the interfering signal drives an open

switch. It is dominated by inductive coupling in the pack-

age lead frame between adjacent leads. It decreases

rapidly as the interfering signal moves further away from

the pin adjacent to the input signal selected. Output

crosstalk is coupling from one driven output to another

active output. It decreases with increasing load imped-

ance as it is caused mainly by ground and power cou-

pling between output amplifiers. If a signal is driving an

open switch, its crosstalk is mainly input crosstalk. If it is

driving a load through an active output, its crosstalk is

mainly output crosstalk.

Input and output crosstalk measurements are performed

with the test configuration shown in Figure 13.

Figure 13. Test Configuration for Crosstalk

For input crosstalk, the switch is open and all inputs are

nal, while all other inputs are AC terminated with 75

Ω. All

outputs are enabled and crosstalk is measured from IN1

to any output.

For output crosstalk, the switch is closed. Crosstalk from

OUT1 to any output is measured.

Crosstalk from multiple sources into a given channel is

measured with the setup shown in Figure 14. Input In1 is

puts Out1 to Out8. Input In9 is driven with a secondary,

asynchronous gray field video signal and is connected to

Out9. All other inputs are AC terminated with 75

Ω.

Crosstalk effects on the gray field are measured and cal-

at the load.

If not all inputs and outputs are needed, avoid using

adjacent channels to reduce crosstalk.

Figure 14. Test Configuration for Multi-Channel

Crosstalk

Bias

IN1

OUT1

Bias

IN8

OUT6

Gain = 6dB

Out1 = 2.0VPP

Input Crosstalk from IN1

to OUTx

Output Crosstalk from

OUT1 to OUTx

TERMINATION

IN2 - IN8 are

AC-Term to

Ground

w/75

IN1 = 1VPP

Open switch

for input

crosstalk.

Close switch

for output

crosstalk.

Bias

IN1

OUT1

Bias

IN8

OUT6

TERMINATION

Bias

IN6

IN1 driven with

SD video 1V

IN6 driven with

asynchronous

SD video 1V

IN2,3,4,5,7,8 are

AC-term to GND

with 75 .

Measure crosstalk from

channels 1-5 into

channel6