ISL28118 Datasheet, PDF (18/23 Pages) Intersil Corporation – 40V Precision Single Supply Rail-to-Rail Output Low Power Operational Amplifiers

ISL28118, ISL28218
Applications Information
Functional Description
The ISL28118 and ISL28218 are single and dual, single
supply rail-to-rail output amplifiers with a common mode
input voltage range extending to 0.5V below the V- rail.
These op amps feature very low quiescent current of
850µV, and low temperature drift. Both devices are
fabricated in a new precision 40V complementary bipolar
DI process and immune from latch-up.
Operating Voltage Range
The devices are designed to operate over the 3V
(±1.5V) to 40V (±20V) range and are characterized at
10V (±5V) and 30V (±15V). Both DC and AC
performance remain virtually unchanged over the
complete operating voltage range. Parameter variation
with operating voltage is shown in the “Typical
Performance Curves” beginning on page 7.
Input Stage Performance
The ISL28118 and ISL28218 PNP input stage provides a
maximum input differential voltage of 42V. The input
stage is capable of below ground sensing. The device is
fully characterized down to half a volt below the V- rail
at +25°C. The input common mode voltage range
sensitivity to temperature is shown in Figure 10 (±15V).
These features provide excellent CMRR, AC performance
and extremely low input distortion over a wide
temperature range.
Input ESD Diode Protection
The PNP input stage has a max input differential voltage
equal to a diode drop greater than the supply voltage
(max 42V). This feature enables the device to function
reliably in large signal pulse applications without the
need for anti-parallel clamp diodes required on MOSFET
and most bipolar input stage op amps. Thus, input signal
distortion caused by nonlinear clamps under high slew
rate conditions are avoided.
In applications where one or both amplifier input
terminals are at risk of exposure to voltages beyond the
supply rails, current limiting resistors may be needed at
each input terminal (see Figure 62 R_IN+, R_IN-) to limit
current through the power supply ESD diodes to 20mA.
V+
V_IN-
R_IN- _-
V_IN+
R_IN+ ₊
R_L
V-
FIGURE 62. INPUT ESD DIODE CURRENT LIMITING
Output Drive Capability
The bipolar rail-to-rail output stage features rail-to-rail
output swing at moderate levels of output current
(Figures 31 through 34).
The output current is internally limited. Output current
limit over-temperature is shown in Figures 31 through 34.
The amplifiers can withstand a short circuit to either rail
as long as the power dissipation limits are not exceeded.
This applies to only 1 amplifier at a time for the dual op
amp. Continuous operation under these conditions may
degrade long term reliability.
Output Phase Reversal
Output phase reversal is a change of polarity in the
amplifier transfer function when the input voltage
exceeds the supply voltage. The ISL28118 and ISL28218
are immune to output phase reversal, out to 0.5V
beyond the rail (V_{ABS MAX}) limit (Figure 49).
Using Only One Channel
The ISL28218 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 inverting input and ground the
positive input (as shown in Figure 63).
-
+
FIGURE 63. PREVENTING OSCILLATIONS IN UNUSED
CHANNELS
18
FN7532.1
November 22, 2010