ISL70244SEH Datasheet, PDF (18/21 Pages) Intersil Corporation – Rail-to-rail input and output

ISL70244SEH
Applications Information
Functional Description
The ISL70244SEH contains two high speed, low power op amps
designed to take advantage of its full dynamic input and output
voltage range with rail-to-rail operation. By offering low power, low
offset voltage and low temperature drift coupled with its high
bandwidth and enhanced slew rates upwards of 50V/µs, these op
amps are ideal for applications requiring both high DC accuracy and
AC performance. The ISL70244SEH is manufactured in Intersil’s
PR40 silicon-on-insulator process, which makes this device immune
to single-event latch-up and provides excellent radiation tolerance.
This makes it the ideal choice for high reliability applications in
harsh radiation-prone environments.
Operating Voltage Range
The devices are designed to operate with a split supply rail from
±1.35V to ±20V or a single supply rail from 2.7V to 40V. The
ISL70244SEH is fully characterized in production for supply rails of
5V (±2.5V) and 36V (±18V). The power supply rejection ratio is
typically 120dB with a nominal ±18V supply. The worst case
common-mode rejection ratio over-temperature is within 1.5V to 2V
of each rail. When V_CM is inside that range, the CMRR performance
is typically >110dB with ±18V supplies. The minimum CMRR
performance over the -55°C to +125°C temperature range and
radiation is >70dB over the full common-mode input range for
power supply voltages from ±2.5V (5V) to ±18V (36V).
Input Performance
The slew enhanced front end is a block that is placed in parallel
with the main input stage and functions based on the input
differential voltage.
Input ESD Diode Protection
The input terminals (IN+ and IN-) have internal ESD protection
diodes to the positive and negative supply rails, series connected
600Ω current limiting resistors and an anti-parallel diode pair
across the inputs.
V+
- ^600Ω
V_IN
+ ^600Ω
V_OUT
R_L
V-
FIGURE 63. INPUT ESD DIODE CURRENT LIMITING, UNITY GAIN
Output Short-Circuit Current Limiting
The output current limit has a worst case minimum limit of
±8mA but may reach as high as ±100mA. The op amp can
withstand a short-circuit to either rail for a short duration (<1s) as
long as the maximum operating junction temperature is not
violated. This applies to only one amplifier at a given time.
Continued use of the device in these conditions may degrade the
long term reliability of the part and is not recommended.
Figure 21 on page 10 shows the typical short-circuit currents that
can be expected. The ISL70244SEH’s current limiting circuitry
will automatically lower the current limit of the device if
short-circuit conditions carry on for extended periods of time in
an effort to protect itself from malfunction. However, extended
operation in this mode will degrade the output rail-to-rail
performance by pulling V_OH/V_OL away from the rails.
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 ISL70244SEH is immune to output phase reversal,
even when the input voltage is 1V beyond the supplies. This is
illustrated in Figure 50 on page 15.
Power Dissipation
It is possible to exceed the +150°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 + _JA x PD_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 = V_S  I_qMAX + V_S - V_OUTMAX   -^V----^O----^U--_R--^T---_L-^M-----^A----^X--
(EQ. 2)
Where:
• T_MAX = Maximum ambient temperature
• _JA = Thermal resistance of the package
• PD_MAX = Maximum power dissipation of 1 amplifier
• V_S = Total supply voltage
• I_qMAX = Maximum quiescent supply current of 1 amplifier
• V_OUTMAX = Maximum output voltage swing of the application
Unused Channel Configuration
The ISL70244SEH is a dual op amp. If the application does not
require the use of both op amps, 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 results in higher-than-expected supply currents and possible
noise injection into the active channel. The proper way to prevent
oscillation is to short the output to the inverting input, and
ground the positive input (Figure 64).
-
+
FIGURE 64. PREVENTING OSCILLATIONS IN UNUSED CHANNELS
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FN8592.2
September 1, 2016