ISL24021_15 Datasheet, PDF (9/13 Pages) Intersil Corporation – 1A Rail-to-Rail Input-Output Operational Amplifier

ISL24021
Applications Information
Product Description
The ISL24021 is a high output current, high voltage, rail-to-rail
voltage feedback amplifier. The ISL24021 is capable of ±1A
peak output short circuit current. The amplifier exhibits beyond
the rail input capability, rail-to-rail output capability and is unity
gain stable. Other features include fast slew rate and settling
time which is important in many applications, such as TFT-LCD
panels.
The ISL24021 is available in a 8 Ld 3mmx3mm TDFN package
featuring a standard operational amplifier pinout and a lead pitch
of 0.65mm. The device utilizes a thermally enhanced package and
has a built-in thermal protection circuit. It is specified for operation
over an ambient temperature range of -40°C to +85°C.
Operating Voltage, Input and Output
Capability
The ISL24021 can operate on a single supply or dual supply
configuration. The ISL24021 operating voltage ranges from a
minimum of 4.5V to a maximum of 19V. This range allows for a
standard 5V (or ±2.5V) supply voltage to dip to -10%, or a
standard 18V (or ±9V) to rise by +5.5% without affecting
performance or reliability.
The input common mode voltage range extends 0.5V beyond the
supply rails. For this range, the ISL24021 amplifier is immune to
phase reversal. If the common mode input voltage exceeds the
supply voltage by more than 0.5V, electrostatic protection diodes
in the input stage of the device begin to conduct. It is suggested
to not overdrive the inputs. Figure 23 shows the input voltage
driven beyond the supply rails and the device output swinging
between the supply rails.
The output swings of the ISL24021 typically extend to within
25mV of positive and negative supply rails with load currents of
±5mA. Decreasing load currents will extend the output voltage
range even closer to the supply rails. Figure 24 shows the input
and output waveforms for the device in a unity-gain
configuration. Operation is from ±5V supply with a 1kΩ load
connected to GND. The input is a 10V_P-P sinusoid and the output
voltage is approximately 9.95V_P-P.
Refer to the “Electrical Specifications” tables beginning on
page 2 for specific device parameters. Parameter variations with
operating voltage, loading and/or temperature are shown in the
“Typical Performance Curves” on page 5.
V_S = ±2.5V, T_A = +25°C, A_V = 1, V_IN = 6V_P-P
1V
10µs
1V
FIGURE 23. OPERATION WITH BEYOND-THE-RAILS INPUT
.
V_S = ±5V, T_A = +25°C, A_V = 1, V_IN = 10V_P-P
5V
10µs
5V
FIGURE 24. OPERATION WITH RAIL-TO-RAIL INPUT AND OUTPUT
Output Current Limit
The ISL24021 is capable of ±1A peak output short circuit
current. The device will limit the current to ±1A. Maximum
reliability is maintained if the output continuous current never
exceeds ±300mA. This limit is set by the characteristics of the
internal metal interconnects. See “Power Dissipation” on
page 10 for detailed information about ensuring device
operation with temperature and load conditions.
Driving Capacitive Loads
As load capacitance increases, the -3dB bandwidth will decrease
and peaking can occur. Depending on the application, it may be
necessary to reduce peaking and to improve device stability. To
improve device stability a snubber circuit or a series resistor may
be added to the output of the ISL24021.
A snubber is a shunt load consisting of a resistor in series with a
capacitor, see Figure 25. An optimized snubber can improve the
phase margin and the stability of the ISL24021. The advantage
of a snubber circuit is that it does not draw any DC load current or
reduce the gain.
Another method to reduce peaking is to add a series output
resistor (typically between 1Ω to 10Ω; see Figure 26). Depending
on the capacitive loading, a small value resistor may be the most
appropriate choice to minimize any reduction in gain.
9
FN6637.1
October 18, 2011