ISL28278, ISL28478
Pin Descriptions
ISL28278
ISL28478
EQUIVALENT
(16 LD QSOP) (16 LD QSOP) PIN NAME
CIRCUIT
Circuit 3
Circuit 1
Circuit 1
Circuit 4
Circuit 1
Circuit 1
Circuit 3
DESCRIPTION
3
1
2
OUT_A
IN-_A
IN+_A
V+
Amplifier A output
4
Amplifier A inverting input
Amplifier A non-inverting input
Positive power supply
5
3
15
4
12
5
IN+_B
IN-_B
OUT_B
NC
Amplifier B non-inverting input
Amplifier B inverting input
Amplifier B output
13
14
6
7
1, 2, 8, 9, 10, 16
8, 9
10
11
12
13
14
15
16
No internal connection
Amplifier C output
OUT_C
IN-_C
IN+_C
V-
Circuit 3
Circuit 1
Circuit 1
Circuit 4
Circuit 1
Circuit 1
Circuit 3
Circuit 2
Amplifier C inverting input
Amplifier B non-inverting input
Negative power supply
Amplifier D non-inverting input
Amplifier D inverting input
Amplifier D output
7
IN+_D
IN-_D
OUT_D
EN_A
6
Amplifier A enable pin internal pull-down; Logic “1” selects the disabled state;
Logic “0” selects the enabled state.
11
EN_B
Circuit 2
Amplifier B enable pin with internal pull-down; Logic “1” selects the disabled
state; Logic “0” selects the enabled state.
V
+
V
V
+
+
V
+
CAPACITIVELY
COUPLED
ESD CLAMP
LOGIC
PIN
OUT
IN-
IN+
V
-
V
-
V
-
V
-
CIRCUIT 1
CIRCUIT 2
CIRCUIT 3
CIRCUIT 4
undesired change in magnitude and polarity of input offset
current.
Applications Information
Introduction
The ISL28278 achieves input rail-to-rail without sacrificing
important precision specifications and degrading distortion
performance. The devices’ input offset voltage exhibits a
smooth behavior throughout the entire common-mode input
range. The input bias current versus the common-mode
voltage range gives us an undistorted behavior from typically
The ISL28278 and ISL28478 are dual and quad CMOS
rail-to-rail input, output (RRIO) micropower operational
amplifiers. These devices are designed to operate from a
single supply (2.4V to 5.0V) or dual supplies (±1.2V to
±2.5V) while drawing only 120μA (ISL28278) of supply
current. This combination of low power and precision
performance makes these devices suitable for solar and
battery power applications.
100mV below the negative rail and 10% higher than the V
+
rail (0.5V higher than V when V equals 5V).
+
+
Input Protection
Rail-to-Rail Input
All input terminals have internal ESD protection diodes to the
positive and negative supply rails, limiting the input voltage to
within one diode beyond the supply rails. There is an
additional pair of back-to-back diodes across the input
terminals. For applications where the input differential voltage
is expected to exceed 0.5V, external series resistors must be
used to ensure the input currents never exceed 5mA.
Many rail-to-rail input stages use two differential input pairs,
a long-tail PNP (or PFET) and an NPN (or NFET). Severe
penalties have to be paid for this circuit topology. As the
input signal moves from one supply rail to another, the
operational amplifier switches from one input pair to the
other causing drastic changes in input offset voltage and an
FN6145.2
July 11, 2007
10
INTERSIL [ Intersil ]
