el2257 Intersil Corporation, el2257 Datasheet - Page 15

• Manufacturer Part Number: el2257
• Description: 125mhz Single Supply, Clamping Op Amp
• Manufacturer: Intersil Corporation

Short Circuit Current Limit
The EL2257 has internal short circuit protection circuitry that
protect it in the event of its output being shorted to either
supply rail. This limit is set to around 100mA nominally and
reduces with increasing junction temperature. It is intended
to handle temporary shorts. If an 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 ±90mA. A
heat sink may be required to keep the junction temperature
below absolute maximum when an output is shorted
indefinitely.
Power Dissipation
With the high output drive capability of the EL2257, it is
possible to exceed the 150°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 power-supply
voltages, load conditions, or package type need to be
modified for the EL2257 to remain in the safe operating area.
The maximum power dissipation allowed in a package is
determined by:
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:
T
T
T
PD
AMAX
JA
JMAX
MAX
PD
= Thermal resistance of the package
MAX
= Maximum junction temperature
= Maximum ambient temperature
= Maximum power dissipation in the package
=
N
PD
u
MAX
V
S
u
I
=
FIGURE 10.
SMAX
T
-------------------------------------------- -
JMAX
15
+
T
V
JA
- T
S
AMAX
- V
OUT
u
V
--------------- -
OUT
R
L
EL2257
where:
If we set the two PD
other, and solve for V
various loads and output voltages according to:
Figure 11 below shows total single supply voltage V
for various output voltage swings for the PDIP and SO
(0.150") packages. The curves assume worst-case
conditions of T
N = Number of amplifiers
V
I
V
R
SMAX
S
OUT
L
= Load resistance tied to ground
= Total supply voltage
V
= Maximum output voltage of the application
= Maximum supply current per amplifier
S
=
--------------------------------------------------------------------------------------------- -
R
---------------------------------------------------------------
A
L
= +85°C a nd I
u
T
MAX
EL2257 Single Supply Voltage
vs. R
V
JMAX
OUT
N
S
, we can get a family of curves for
I
u
S
Load
and Packages
equations, [1] and [2], equal to each
T
FIGURE 11.
u
JA
- T
R
for Various
L
AMAX
+
S
V
= 6.5mA per amplifier.
OUT
+
V
OUT
2
S
vs. R
L