ISL28258 Intersil Corporation, ISL28258 Datasheet - Page 13

• Manufacturer Part Number: ISL28258
• Description: (ISL28158 / ISL28258) Micro-power Single and Dual Precision Rail-to-Rail Input-Output (RRIO) Low Input Bias Current Op Amps
• Manufacturer: Intersil Corporation

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Using Only One Channel
The ISL28258 is a dual op amp. If the application only
requires one channel, the user must configure the unused
channel to prevent it from oscillating. The unused channel
will oscillate if the input and output pins are floating. This will
result in higher than expected supply currents and possible
noise injection into the channel being used. The proper way
to prevent this oscillation is to short the output to the
negative input and ground the positive input (as shown in
Figure 45).
Current Limiting
These devices have no internal current-limiting circuitry. If
the output is shorted, it is possible to exceed the Absolute
Maximum Rating for output current or power dissipation,
potentially resulting in the destruction of the device.
FIGURE 45. PREVENTING OSCILLATIONS IN UNUSED
CHANNELS
+
-
13
ISL28158, ISL28258
Power Dissipation
It is possible to exceed the +125°C maximum junction
temperatures under certain load and power-supply
conditions. It is therefore important to calculate the
maximum junction temperature (T
to determine if power supply voltages, load conditions, or
package type need to be modified to remain in the safe
operating area. These parameters are related in Equation 1:
where:
• P
• PD
where:
• T
• θ
• PD
• V
• I
• V
• R
T
PD
JMAX
dissipation of each amplifier in the package (PD
Equation 2:
application
MAX
MAX
JA
DMAXTOTAL
MAX
S
OUTMAX
L
MAX
MAX
= Load resistance
= Supply voltage (Magnitude of V
= Thermal resistance of the package
=
= Maximum supply current of 1 amplifier
=
= Maximum ambient temperature
T
for each amplifier can be calculated using
= Maximum power dissipation of 1 amplifier
2*V
MAX
= Maximum output voltage swing of the
S
+
×
is the sum of the maximum power
(
I
θ
SMAX
JA
xPD
+
MAXTOTAL
(
V
S
- V
OUTMAX
JMAX
)
+
) for all applications
and V
)
×
V
--------------------------- -
OUTMAX
-
)
R
February 11, 2008
L
MAX
(EQ. 2)
(EQ. 1)
FN6377.2
)