LMH6574 Datasheet, PDF (17/27 Pages) National Semiconductor (TI) – 4:1 High Speed Video Multiplexer

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LMH6574
SNCS103D – NOVEMBER 2004 – REVISED DECEMBER 2014
Typical Application (continued)
Figure 31 shows typical transition waveforms and shows that SD pin switching settles in less than 145 ns.
4.5
1.5
145 ns
4
1
3.5
3
0.5
SD_MUX1
2.5
SD_MUX2
OUT
2
0
1.5
-0.5
1
Settled final value
0.5
-1
0
-0.5
-1.5
-1E-07
-5E-08
0
5E-08 0.0000001 1.5E-07 0.0000002 2.5E-07
Time (50 ns/div)
Figure 31. SD Pin Switching Waveform and Output Settling
If it is important in the end application to make sure that no two inputs are presented to the output at the same
time, an optional delay block can be added, to drive the SHUTDOWN pin of each device. Figure 32 shows one
possible approach to this delay circuit. The delay circuit shown will delay SHUTDOWN's H to L transitions (R1
and C1 decay) but will not delay its L to H transition. R2 should be kept small compared to R1 in order to not
reduce the SHUTDOWN voltage and to produce little or no delay to SHUTDOWN.
R₂ D₁
TO SD
C₁
R₁
Figure 32. Delay Circuit Implementation
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