ADA4830-1WBCPZ-R7 datasheet(16/22 Pages) AD

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ADA4830-1/ADA4830-2

Data Sheet

Rev. C | Page 16 of 22

USING THE ADA4830-2 AS A LOW COST VIDEO

SWITCH

Figure 34 shows a video multiplexer/switch using the ADA4830-2,

dual, high speed difference amplifier. This circuit allows the user

to input two remote video sources into a single channel of a video

decoder, such as the ADV7180.

Traditional CMOS multiplexers and switches suffer several

disadvantages at video frequencies where their on-resistance

introduces distortion, degrades differential gain and phase

performance, and interacts with the termination resistor to

attenuate the incoming video signal and affect the luminance.

System designers generally address these issues by adding

external buffers to add gain and increase drive capability.

Video multiplexing can be simplified by using high speed video

amplifiers with a disable/enable function (sometimes called power-

down). When the amplifier is disabled, its output stage goes into

a high impedance state, allowing several amplifier outputs to be

wired together. High speed video op amps have all the key features

required to make them ideal for this function. Their high input

impedance does not affect the characteristic impedance of the

transmission line, thus allowing back termination. They also have

inherently good video specifications, including differential gain and

phase, slew rate, bandwidth, and 0.1 dB flatness.

Each channel of the ADA4830-2 is a high speed difference

amplifier circuit that eliminates common-mode noise and phase

noise caused by ground potential differences between the incoming

video signal and the receiver. The ADA4830-2 also offers integrated

short-to-battery protection and heightened ESD tolerance in a

small foot print. The fault detection output (the STB pins) of the

ADA4830-2 allows for proactive wire diagnostics when connected

to a microcontroller or video decoder and are used to generate

an interrupt during a fault condition.

ADA4830-2

INP1

0.1µF

ENABLE2

(INPUT)

+VS

4.7µF

VOUT1

VOUT2

STB1

STB2

Ω

+VS

75Ω

DIFFERENTIAL

INPUT 1

75Ω

DIFFERENTIAL

INPUT 2

CONNECT

TO VIDEO

DECODER

75Ω

INN1

INN2

INP2

STB FLAGS

(OUTPUTS)

2.2µF

0.1µF

ENABLE1

(INPUT)

Figure 34. Low Cost Video Switch Using the ADA4830-2

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