MAX4032
5V, 6dB Video Buffer with Sync-Tip Clamp,
Output Sag Correction, and 150nA Shutdown Current
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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
