MAX4032 데이터 시트보기 (PDF) - Maxim Integrated

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MAX4032

5V, 6dB Video Buffer with Sync-Tip Clamp, Output Sag Correction, and 150nA Shutdown Current

Maxim Integrated 

5V, 6dB Video Buffer with Sync-Tip Clamp,

Output Sag Correction, and 150nA Shutdown Current

voltage is close to the rated voltage of the capacitor, a

film dielectric is recommended. Increasing the capaci-

tor value slows the clamp capture time. Values above

0.5µF should be avoided since they do not improve the

clamp’s performance.

The active sync-tip clamp also requires that the input

impedance seen by the input capacitor be less than

100Ω typically to function properly. This is easily met by

the 75Ω input resistor prior to the input-coupling capac-

itor and the back termination from a prior stage.

Insufficient input resistance to ground causes the

MAX4032 to appear to oscillate. Never operate the

MAX4032 in this mode.

Output Coupling the MAX4032

The output of the MAX4032 can be AC- or DC-coupled

to the load. In the DC-coupled mode, the MAX4032

provides accurate sync-tip clamping for single-supply

operation and still can drive a 150Ω, back-terminated

load. In the AC-coupled mode, the MAX4032 allows the

use of minimal size capacitors to drive a back-terminat-

ed video load of 150Ω.

DC-Coupling the Output

By shorting SAG to OUT, the device becomes an ampli-

fier with DC restore, optimally placing the video within

the dynamic range of the output. In this mode, the

MAX4032 can be used as the input conditioner for a

video signal, providing gain and biasing in single-sup-

ply applications. DC-coupling also improves the

MAX4032’s performance in terms of differential gain

and phase. This reflects the improvement in the low-fre-

quency response due to DC-coupling.

AC-Coupling the Output

The MAX4032’s output is configured to support AC-

coupling with minimal capacitance. This is called “sag

correction.” It refers to the improved bandwidth

achieved by using two smaller capacitors to replace a

single large capacitor shown in Figure 3.

Layout and Power-Supply Bypassing

The MAX4032 operates from a single 5V supply.

Bypass the supply with a 0.1µF capacitor as close to

the pin as possible. Maxim recommends using

microstrip and stripline techniques to obtain full band-

width. To ensure that the PC board does not degrade

the device’s performance, design it for a frequency

greater than 1GHz. Pay careful attention to inputs and

outputs to avoid large parasitic capacitance. Whether

or not you use a constant-impedance board, observe

the following design guidelines:

• Do not use wire-wrap boards; they are too inductive.

• Do not use IC sockets; they increase parasitic capac-

itance and inductance.

• Use surface-mount instead of through-hole compo-

nents for better, high-frequency performance.

• Use a PC board with at least two layers; it should be

as free from voids as possible.

• Keep signal lines as short and as straight as possible.

Do not make 90° turns; round all corners.

Chip Information

TRANSISTOR COUNT: 755

PROCESS: BiCMOS

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