MAX442CPA Maxim Integrated Products, MAX442CPA Datasheet - Page 7

• Manufacturer Part Number: MAX442CPA
• Description: IC MUX/VIDEO AMP 2CH 140MHZ 8DIP
• Manufacturer: Maxim Integrated Products

Specifications of MAX442CPA

• Applications: 2:1 Multiplexer-Amplifier
• Number Of Circuits: 1
• -3db Bandwidth: 140MHz
• Slew Rate: 250 V/µs
• Current - Supply: 30mA
• Voltage - Supply, Single/dual (±): ±4.75 V ~ 5.25 V
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

The Typical Operating Circuit shows the MAX442 dri-
ving a back-terminated 75Ω video cable. The back-ter-
mination resistor (at the MAX442 output) is included to
match the impedance of the cable’s driven end to the
characteristic impedance of the cable itself. This, plus
the load-termination resistor, eliminates signal reflec-
tions from the cable’s ends. The back-termination resis-
tor forms a voltage divider with the load impedance,
which attenuates the signal at the cable output by one-
half. The amplifier is operated with a 2V/V closed-loop
gain to provide unity gain at the cable’s video output.
Driving large capacitive loads increases the likelihood
of oscillation in most amplifier circuits. This is especial-
ly true for circuits with high loop gains, like voltage fol-
140MHz, 2-Channel
Video Multiplexer/Amplifier
Figure 2. Capacitive-Load-Driving Circuit
Figure 3. Output Switching Transient when Switching Between
Two Grounded Inputs with R
6
200mV/div
A0 INPUT
OUTPUT
_______________________________________________________________________________________
5V/div
AMP
IN
MAX442
Capacitive-Load Driving
L
= 100 Ω
22
C
LOAD
OUT
> 50pF
GND
GND
lowers. The amplifier’s output impedance and the
capacitive load form an RC filter that adds a pole to the
loop response. If the pole frequency is low enough, as
when driving a large capacitive load, the circuit phase
margin is degraded and oscillation may occur.
With capacitive loads greater than approximately 50pF
and the MAX442 configured as a unity-gain buffer, use
an isolation resistor in series with the load, as shown in
Figure 2. The resistor removes the pole from the loop
response caused by the load capacitance.
When the MAX442 multiplexer is switched from one
channel to another, a small glitch will appear at the out-
put. Figure 3 shows the results of putting a 0V to 5V
pulse 100ns wide into A0.
Figure 4. Pulse Response with R
cable), A
Figure 5. Pulse Response with R
cable), A
500mV/div
OUTPUT
OUTPUT
CABLE
CABLE
INPUT
INPUT
1V/div
1V/V
1V/V
VCL
VCL
Channel Switching Time/Transient
= +1V/V
= +2V/V
L
L
= 100 Ω (50 Ω back-terminated
= 100 Ω (50 Ω back-terminated
GND
GND
GND
GND