el2160 Intersil Corporation, el2160 Datasheet - Page 12

• Manufacturer Part Number: el2160
• Description: 180mhz Current Feedback Amplifier
• Manufacturer: Intersil Corporation

Power Dissipation
The EL2160 amplifier combines both high speed and large
output current drive capability at a moderate supply current
in very small packages. It is possible to exceed the maximum
junction temperature allowed under certain supply voltage,
temperature, and loading conditions. To ensure that the
EL2160 remains within its absolute maximum ratings, the
following discussion will help to avoid exceeding the
maximum junction temperature.
The maximum power dissipation allowed in a package is
determined by its thermal resistance and the amount of
temperature rise according to:
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:
where I
quiescent supply current flowing in the output driver
transistor should be subtracted from the first term because,
under loading and due to the class AB nature of the output
stage, the output driver current is now included in the second
term.)
In general, an amplifier's AC performance degrades at
higher operating temperature and lower supply current.
Unlike some amplifiers, the EL2160 maintains almost
constant supply current over temperature so that AC
performance is not degraded as much over the entire
operating temperature range. Of course, this increase in
performance doesn't come for free. Since the current has
increased, supply voltages must be limited so that maximum
power ratings are not exceeded.
The EL2160 consumes typically 8.5mA and maximum
11.0mA. The worst case power in an IC occurs when the
output voltage is at half supply, if it can go that far, or its
maximum values if it cannot reach half supply. If we set the
two P
we can get a family of curves for various loads and output
voltages according to:
The following curves show supply voltage (±V
for various output voltage swings for the 2 different
V
S
=
DMAX
S
R
-------------------------------------------------------- -
L
is the supply current. (To be more accurate, the
u
P
equations equal to each other, and solve for V
DMAX
T
MAX
T
JA
P
-T
DMAX
=
AMAX
2
u
V
=
S
+
T
-------------------------------------------- -
+
12
JMAX
V
V
OUT
S
–
T
–
JA
V
T
OUT
y
AMAX
>
2
u
u
I
V
--------------- -
S
OUT
R
u
S
L
R
) vs R
L
+
V
LOAD
OUT
S
@
,
EL2160
packages. The curves assume worst case conditions of
T
The curves do not include heat removal or forcing air, or the
simple fact that the package will probably be attached to a
circuit board, which can also provide some form of heat
removal. Larger temperature and voltage ranges are
possible with heat removal and forcing air past the part.
Current Limit
The EL2160 has an internal current limit that protects the
circuit in the event of the output being shorted to ground.
This limit is set at 100mA nominally and reduces with
junction temperature. At a junction temperature of 150°C , the
current limits at about 65mA. If the output is shorted to
ground, the power dissipation could be well over 1W. Heat
removal is required in order for the EL2160 to survive an
indefinite short.
Driving Cables and Capacitive Loads
When used as a cable driver, double termination is always
recommended for reflection-free performance. For those
applications, the back termination series resistor will
decouple the EL2160 from the capacitive cable and allow
extensive capacitive drive. However, other applications may
have high capacitive loads without termination resistors. In
these applications, an additional small value (5:–50:)
resistor in series with the output will eliminate most peaking.
A
= +85°C and I
S
= 11mA.
Supply Voltage vs R
Various V
Supply Voltage vs R
Various V
OUT
OUT
(8-Pin SO Package)
(PDIP Package)
LOAD
LOAD
for
for