MAX11505 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX11505

Four-Channel, Standard-Definition Video Filters

Maxim Integrated 

Four-Channel, Standard-Definition

Video Filters

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

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

ensure that the transparent clamp remains off. A suit-

able network is shown in Figure 4. Determine the bias

voltage using:

VB

=

R2

R1+ R2

(VCC

−

IL × R1)

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

resistor, an optional 220µF or larger coupling

capacitor, and a 75Ω termination resistor. The

MAX11504/MAX11505 clamp the signal, forcing the

blanking level to less than 1V at the termination resis-

tor. This allows driving video loads to meet digital TV

specifications without the need for costly AC-coupling

capacitors. When driving two parallel loads per output

(Figure 5b), thermal considerations must be taken into

account, especially for DC-coupled outputs (see the

Junction Temperature Calculations section.)

ENCODER

DAC

VCC

R1

820kΩ

0.1µF

MAX11504

MAX11505

IN_

R2

120kΩ

MAX11504

MAX11505

OUT_

75Ω

220µF

(OPTIONAL)

75Ω

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

Standard-Definition Filters

The MAX11504/MAX11505 filters are optimized to deliv-

er a flat passband along with high stopband attenua-

tion. The filter characteristic has been chosen to provide

an excellent time domain response with low overshoot.

The typical -3dB frequency of 8.6MHz guarantees mini-

mal attenuation in the passband while at the same time

offering a 27MHz attenuation of typically -50dB.

Channel 1 of the MAX11505 has 0.8dB of high-frequency

boost and a -3dB frequency of 8.9MHz.

Output Buffer

The MAX11504/MAX11505 feature output buffers with

+6dB gain that drive two standard 150Ω video loads.

A typical load (Figure 5a) is a 75Ω back-match

(a)

MAX11504

MAX11505

OUT_

75Ω 220µF

(OPTIONAL)

75Ω

75Ω 220µF

(OPTIONAL)

75Ω

(b)

Figure 5. Typical Output Loads

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