9

FN7309.8

September 14, 2010

Description of Operation and Application

Information

Product Description

The EL5170 and EL5370 are wide bandwidth, low power

and single/differential ended to differential output amplifiers.

They have a fixed gain of 2. The EL5170 is a single channel

differential amplifier. The EL5370 is a triple channel

differential amplifier. The EL5170 and EL5370 have a -3dB

bandwidth of 100MHz while driving a 200

Ω differential load.

The EL5170 and EL5370 are available with a power-down

feature to reduce the power while the amplifiers are

disabled.

Input, Output and Supply Voltage Range

The EL5170 and EL5370 have been designed to operate

with a single supply voltage of 5V to 10V or 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 3.8V. If the

input common mode or differential mode signal is outside the

above-specified ranges, it will cause the output signal to

become distorted.

The output of the EL5170 and EL5370 can swing from -3.3V

to 3.6V at 200

Ω differential load at ±5V supply. As the load

resistance becomes lower, the output swing is reduced.

Differential and Common Mode Gain Settings

As shown in the “Simplified Schematic” on page 8, since the

200

Ω and 400Ω, the EL5170 and EL5370 have a fixed gain of

2. The common mode gain is always one.

Driving Capacitive Loads and Cables

The EL5170 and EL5370 can drive 75pF differential

capacitor in parallel with 200

Ω differential load with less than

3.5dB of peaking. If less peaking is desired in applications, a

small series resistor (usually between 5

Ω 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.

Disable/Power-Down

The EL5170 and EL5370 can be disabled and their outputs

placed in a high impedance state. The turn-off time is about

1µs and the turn-on time is about 200ns. When disabled, the

power consumption. The amplifier’s power-down can be

controlled by standard CMOS signal levels at the ENABLE

EN pin float or applying a signal that is less than 1.5V below

Output Drive Capability

The EL5170 and EL5370 have internal short circuit

protection. Its typical short circuit current is ±80mA. If the

output is shorted indefinitely, the power dissipation could

easily increase such that the part will be destroyed.

Maximum reliability is maintained if the output current never

exceeds ±60mA. This limit is set by the design of the internal

metal interconnect.

Power Dissipation

With the high output drive capability of the EL5170 and

EL5370 it is possible to exceed the +125°C absolute

maximum junction temperature under certain load current

conditions. Therefore, it is important to calculate the maximum

junction temperature for the application to determine if the

load conditions or package types need to be modified for the

amplifier to remain in the safe operating area.

The maximum power dissipation allowed in a package is

determined according to Equation 1:

Where:

The maximum power dissipation actually produced by an IC

is the total quiescent supply current times the total power

supply voltage, plus the power in the IC due to the load, or

as expressed in Equation 2:

Where:

application

i = Number of channels

–

Θ

JA

---------------------------------------------

=

(EQ. 1)

PD

i

ΔV

O

------------

×

+

×

⎝⎠

⎜⎟

⎛⎞

×

=

(EQ. 2)

EL5170, EL5370