EL5173, EL5373
Simplified Schematic
200Ω
V
S
+
R
3
R
7
R
4
R
8
R
1
R
2
IN+
IN-
FBP
FBN
V
B1
OUT+
R
CD
R
CD
REF
R
9
R
10
C
C
V
B2
C
C
R
5
V
S
-
R
6
OUT-
400Ω
200Ω
Description of Operation and Application
Information
Product Description
The EL5173 and EL5373 are wide bandwidth, low power
and single/differential ended to differential output amplifiers.
They have a fixed gain of 2. The EL5173 is a single channel
differential amplifier. The EL5373 is a triple channel
differential amplifier. The EL5173 and EL5373 have a –3dB
bandwidth of 450MHz while driving a 200Ω differential load.
The EL5173 and EL5373 are available with a power down
feature to reduce the power while the amplifiers are
disabled.
Driving Capacitive Loads and Cables
The EL5173 and EL5373 can drive 16pF differential
capacitor in parallel with 200Ω differential load with less than
3.5dB of peaking. If less peaking is desired in applications, a
small series resistor (usually between 5Ω to 50Ω) can be
placed in series with each output to eliminate most peaking.
However, this will reduce the gain slightly.
When used as a cable driver, double termination is always
recommended for reflection-free performance. For those
applications, a back-termination series resistor at the
amplifier’s output will isolate the amplifier from the cable and
allow extensive capacitive drive. However, other applications
may have high capacitive loads without a back-termination
resistor. Again, a small series resistor at the output can help
to reduce peaking.
Input, Output and Supply Voltage Range
The EL5173 and EL5373 have been designed to operate
with a single supply voltage of 5V to 10V or a split supplies
with its total voltage from 5V to 10V. The amplifiers have an
input common mode voltage range from -4.5V to 3.4V for
±5V supply. The differential mode input range (DMIR)
between the two inputs is from –2.3V to +2.3V. The input
voltage range at the REF pin is from –3.3V to 3.7V. If the
input common mode or differential mode signal is outside the
above-specified ranges, it will cause the output signal
distorted.
The output of the EL5173 and EL5373 can swing from –3.3V
to 3.6V at 200Ω differential load at ±5V supply. As the load
resistance becomes lower, the output swing is reduced.
Disable/Power-Down
The EL5173 and EL5373 can be disabled and placed their
outputs in a high impedance state. The turn off time is about
1.2µs and the turn on time is about 100ns. When disabled,
the amplifier’s supply current is reduced to 40µA for I
S
+ and
2.5µA for I
S
- typically, thereby effectively eliminating the
power consumption. The amplifier’s power down can be
controlled by standard CMOS signal levels at the ENABLE
pin. The applied logic signal is relative to V
S
+ pin. Letting the
EN pin float or applying a signal that is less than 1.5V below
V
S
+ will enable the amplifier. The amplifier will be disabled
when the signal at EN pin is above V
S
+ -0.5V.
Differential and Common Mode Gain Settings
As shown at the simplified schematic, since the feedback
resistors RF and the gain resistor are integrated with 200Ω
and 400Ω, the EL5173 and EL5373 have a fixed gain of 2.
The common mode gain is always one.
Output Drive Capability
The EL5173 and EL5373 have internal short circuit
protection. Its typical short circuit current is ±55mA. If the
output is shorted indefinitely, the power dissipation could
easily increase such that the part will be destroyed.
9
FN7312.4
February 16, 2005
INTERSIL [ INTERSIL CORPORATION ]
