Three-Channel,

Standard-Definition Video Filters

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7

Standard-Definition Filters

The MAX11501/MAX11502 filters are optimized to deliver

a flat (MAX11501) or high-frequency boosted (MAX11502)

passband and high stopband attenuation. The filter char-

acteristics have been chosen to provide excellent time

domain response with low overshoot. The typical -3dB fre-

quency of 8.6MHz (MAX11501) and 8.9MHz (MAX11502)

guarantee minimal attenuation in the passband while

at the same time offering a 27MHz attenuation of

typically -50dB (MAX11501) and -48dB (MAX11502).

Output Buffer

The MAX11501/MAX11502 feature output buffers with

+6dB of gain. A typical load (Figure 5(a)) is a 75Ω back-

match resistor, an optional 220µF or larger AC-coupling

capacitor, a transmission line, and a 75Ω termination

resistor. The MAX11501/MAX11502 clamp the signal,

forcing the blanking level to less than 1V at the termina-

tion resistor. This allows direct drive of video loads at

digital TV specifications without the need for costly AC-

coupling capacitors. The MAX11501/MAX11502 drive

two parallel loads per output (Figure 5(b)), but thermal

considerations must be taken into account when doing

so (see the

Junction-Temperature Calculations section).

Applications Information

Output Configuration

The MAX11501/MAX11502 outputs may be either DC- or

AC-coupled. When the outputs are AC-coupled, choose

a capacitor that passes the lowest frequency content of

the video signal, and keeps the line-time distortion within

desired limits. The capacitor value is a function of the

input leakage and impedance of the circuit being driven.

The MAX11501/MAX11502 easily drive the industry com-

mon 220µF, or larger, coupling capacitor. If any or all

outputs are driving two parallel loads, see the

Junction-

Temperature Calculations section.

The MAX11501/MAX11502 outputs are fully protected

against short circuits to ground. The short-circuit pro-

tection circuitry limits the output current to 80mA (typi-

cal) per output. Shorting more than one output to

ground simultaneously may exceed the maximum

package power dissipation.

Junction-Temperature Calculations

Die temperature is a function of quiescent power dissi-

pation and the power dissipation in the output drivers.

and given by:

ver stage and given by:

load resistance.

The following is an example of a junction-temperature

calculation, assuming the following conditions:

1) Video standard = 525/60/2:1.

2) Video format = RGB with syncs on all.

3) Picture content = 100% white.

4) The input signal is AC-coupled.

5) The output signal is DC-coupled.

P

VV

V

R

DOn

CC

ORMSn

ORMSn

Ln

=

−

MAX11501

MAX11502

220

μF

(OPTIONAL)

75

Ω

75

Ω

OUT_

220

μF

(OPTIONAL)

75

Ω

75

Ω

MAX11501

MAX11502

OUT_

(a)

(b)

220

μF

(OPTIONAL)

75

Ω

75

Ω

Figure 5. Typical Output Loads