MAX4444/MAX4445
Ultra-High-Speed, Low-Distortion, Differential-
to-Single-Ended Line Receivers with Enable
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implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
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_______________Detailed Description
The MAX4444/MAX4445 differential-to-single-ended
line receivers offer high-speed and low-distortion per-
formance, and are ideally suited for video and RF sig-
nal-processing applications. These receivers offer a
small-signal bandwidth of 550MHz and have a high
slew rate of up to 5000V/µs. Their 120mA output capa-
bility allows them to be directly coupled to data acquisi-
tion systems.
__________Applications Information
Grounding Bypassing
Use the following high-frequency design techniques
when designing the PC board for the MAX4444/
MAX4445.
• Use a multilayer board with one layer dedicated as
the ground plane.
• Do not use wire wrap or breadboards due to high
inductance.
• Avoid IC sockets due to high parasitic capacitance
and inductance.
• Bypass supplies with a 0.1µF capacitor. Use sur-
face-mount capacitors to minimize lead inductance.
• Keep signal lines as short and straight as possible.
Do not make 90° turns. Use rounded corners. Do not
cross signal paths if possible.
• Ensure that the ground plane is free from voids.
Low-Power Enable Mode
The MAX4444/MAX4445 are disabled when EN goes
low. This reduces supply current to only 3.5mA. As the
output becomes higher impedance, the effective
impedance at the output for the MAX4444 is 1.8kΩ. The
effective output impedance for the MAX4445 is 1.8kΩ
plus R
GAIN
.
Setting Gain (MAX4445)
The MAX4445 is stable with a minimum gain configura-
tion of +2V/V. R
GAIN
, connected between the RG pins,
sets the gain of this device as shown in Figure 1.
Calculate the expected gain as follows:
Gain = (1 + 600 / R
GAIN
)
Driving Capacitive Loads
The MAX4444/MAX4445 are designed to drive capaci-
tive loads. However, excessive capacitive loads may
cause ringing or instability at the output as the phase
margin of the device reduces. Adding a small series
isolation resistor at the output helps reduce the ringing
but slightly increases gain error (Figure 2). For recom-
mended values, see
Typical Operating Characteristics
.
Coaxial Line Driver
The MAX4444/MAX4445 are well suited to drive coaxial
cables. Their high output current capability can easily
drive the 75Ω characteristic impedance of common
coaxial cables. Adjust the gain of the MAX4445 to com-
pensate for cable losses to maintain the required levels
at the input of the next stage.
Figure 1. Setting the Amplifier Gain Figure 2. Using an Isolation Resistor for High Capacitive Loads
Chip Information
TRANSISTOR COUNT: 254
SUBSTRATE CONNECTED TO V
EE
