MAX11507 查看數據表（PDF） - Maxim Integrated

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MAX11507

Low-Cost, 6-Channel SD Plus HD/SD Selectable Video Filters and Buffers

Maxim Integrated 

Low-Cost, 6-Channel SD Plus HD/SD

Selectable Video Filters and Buffers

AC-Coupled Inputs

When the input is AC-coupled, the transparent clamps

are active and set the lowest point of the signal at ground.

This is appropriate for unipolar signals such as CVBS, Y,

R, G, or B, with or without sync pulses (Figure 3).

For bipolar signals such as Pb and Pr, bias the AC-cou-

pled inputs to a fixed DC voltage, typically 0.59V, to

ensure that the transparent clamp remains off. Figure 4

shows a typical network. Determine the bias voltage using:

VB

=

R2

R1+ R2

x

(VAVCC

−

(IL

x

R1))

where IL is the input leakage current (typically 0.5µA).

SD Filters

The MAX11506/MAX11507 filters are optimized to deliv-

er a flat (MAX11506) or high-frequency boosted

(MAX11507) passband and high stopband attenuation.

The filter characteristic provides excellent time domain

response with low overshoot. The typical -3dB frequen-

cy of 9.0MHz guarantee minimal attenuation in the

passband, while at the same time offering a 27MHz

attenuation of typically -48dB.

HD Filters

The internal filters deliver a flat passband along with high

stopband attenuation. The filter characteristic provides

an excellent time domain response with low overshoot.

The typical -3dB frequency of 33MHz guarantees low

attenuation in the passband, while at the same time

allowing for a typical attenuation of -46dB at 74.25MHz.

Output Buffers

The MAX11506/MAX11507 feature output buffers with

+6dB gain that drive a standard 150Ω video load. A

typical load consists of a 75Ω backmatch resistor, an

optional 220µF or larger coupling capacitor, and a 75Ω

termination resistor. The offset between input and out-

put signals ensures that the blanking level on the output

is less than 1V after the backmatch resistor, thus meet-

ing digital TV specifications allowing the devices to

drive video loads directly without using costly AC-coupling

capacitors.

ENCODER

DAC

MAX11506

0.1µF

MAX11507

INPUT

Figure 3. Simple AC-Coupling for Unipolar Signals (CVBS, Y, R,

G, B)

ENCODER

DAC

0.1µF

VCC

R1

820kΩ

MAX11506

MAX11507

INPUT

R2

120kΩ

Figure 4. AC-Coupling for Bipolar Signals (C, Pb, Pr)

Applications Information

Output Considerations

The MAX11506/MAX11507 outputs may be DC- or AC-

coupled. These devices, with +6dB gain, are typically

connected to a 75Ω series backmatch resistor followed

by the video cable. Choose an AC-coupling capacitor

value that ensures that the lowest frequency content in

the video signal is passed and the field-time distortion

is kept within desired limits when using an AC connec-

tion. The selection of this value is a function of the input

impedance, and more importantly, the input leakage of

the circuit being driven. Common industry practice is to

use a 220µF or larger capacitor.

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