ISL28146 Datasheet, PDF (12/15 Pages) Intersil Corporation – 5MHz, Single and Dual Rail-to-Rail Input-Output (RRIO) Op Amps

ISL28146, ISL28246
up with the IN+ signal, a differential voltage results, and
visible distortion occurs on the input and output signals.
To avoid this issue, keep the input slew rate below
1.9V/µs, or use appropriate current limiting resistors.
Large (>2V) differential input voltages can also cause an
increase in disabled I_CC.
Using Only One Channel
The ISL28246 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 (Figure 37).
-
+
FIGURE 37. PREVENTING OSCILLATIONS IN UNUSED
CHANNELS
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.
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_JMAX) for all applications
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 using
Equation 1:
T_JMAX = T_MAX + (θ_JAxPD_MAXTOTAL)
(EQ. 1)
where:
• P_DMAXTOTAL is the sum of the maximum power
dissipation of each amplifier in the package (PD_MAX)
• PD_MAX for each amplifier can be calculated using
Equation 2:
PD_MAX
=
2*V_S × I_SMAX + (V_S
-
V_OUTMAX
)
×
V_{-----O----U----T----M-----A----X--}
R_L
(EQ. 2)
where:
• T_MAX = Maximum ambient temperature
• θ_JA = Thermal resistance of the package
• PD_MAX = Maximum power dissipation of 1 amplifier
• V_S = Supply voltage (Magnitude of V₊ and V_-)
• I_MAX = Maximum supply current of 1 amplifier
• V_OUTMAX = Maximum output voltage swing of the
application
• R_L = Load resistance
12
FN6321.2
February 11, 2008