EL5444CSZ datasheet(18/19 Pages) INTERSIL

18 / 19 page

graph of propagation delay vs. overdrive as a square wave is

presented at the input of the comparator.

Multiplexing with the EL5144 Series Amplifier

Besides normal power down usage, the CE pin on the

EL5146 and EL5246 series amplifiers also allow for

multiplexing applications. Figure 5 shows an EL5246 with its

outputs tied together, driving a back terminated 75

Ω video

load. A 3VP-P 10MHz sine wave is applied at Amp A input,

and a 2.4VP-P 5MHz square wave to Amp B. Figure 6

shows the SELECT signal that is applied, and the resulting

output waveform at VOUT. Observe the break-before-make

operation of the multiplexing. Amp A is on and VIN1 is being

passed through to the output of the amplifier. Then Amp A

turns off in about 10ns. The output decays to ground with an

RLCL time constants. 500ns later, Amp B turns on and VIN2

is passed through to the output. This break-before-make

operation ensures that more than one amplifier isn’t trying to

drive the bus at the same time. Notice the outputs are tied

directly together. Isolation resistors at each output are not

necessary.

Free Running Oscillator Application

Figure 7 is an EL5144 configured as a free running oscillator.

To first order, ROSC and COSC determine the frequency of

oscillation according to:

For rail to rail output swings, maximum frequency of

oscillation is around 15MHz. If reduced output swings are

acceptable, 25MHz can be achieved. Figure 8 shows the

–

EL5146

+5V

VIN

+2.5V

VOUT

0.1µF

Propagation Delay vs. Overdrive for Amplifier

Used as a Comparator

0.01

0.1

1.0

100

1000

Overdrive (V)

Negative Going Signal

Positive Going Signal

FIGURE 3.

FIGURE 4.

Select

+5V

VOUT

150

Ω

VIN 1

3VPP

10MHz

0.1µF

4.7µF

VIN 2

2.4VPP

5MHz

EL5246

FIGURE 6.

VOUT

Select

FIGURE 5.

OSC

0.72

OSC

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EL5144, EL5146, EL5244, EL5246, EL5444

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