R2

D1

C1

R1

TO SD

-1.5

-1

-0.5

0

0.5

1

1.5

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

-1E-07

-5E-08

0

5E-08

0.0000001

1.5E-07

0.0000002

2.5E-07

Time (50 ns/div)

SD_MUX1

SD_MUX2

OUT

145 ns

Settled final value

19

LMH6574

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SNCS103E – NOVEMBER 2004 – REVISED AUGUST 2018

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Application Information (continued)

Figure 33 shows typical transition waveforms and shows that SD pin switching settles in less than 145 ns.

Figure 33. 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 34 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.

Figure 34. Delay Circuit Implementation