ISL28278_07 Datasheet, PDF (10/13 Pages) Intersil Corporation – Dual and Quad Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Op-Amp

ISL28278, ISL28478
Pin Descriptions
ISL28278
ISL28478
(16 LD QSOP) (16 LD QSOP)
3
1
4
2
5
3
15
4
12
5
13
6
14
7
1, 2, 8, 9, 10, 16
8, 9
10
11
12
7
13
14
15
16
6
11
PIN NAME
OUT_A
IN-_A
IN+_A
V+
IN+_B
IN-_B
OUT_B
NC
OUT_C
IN-_C
IN+_C
V-
IN+_D
IN-_D
OUT_D
EN_A
EN_B
EQUIVALENT
CIRCUIT
DESCRIPTION
Circuit 3 Amplifier A output
Circuit 1 Amplifier A inverting input
Circuit 1 Amplifier A non-inverting input
Circuit 4 Positive power supply
Circuit 1 Amplifier B non-inverting input
Circuit 1 Amplifier B inverting input
Circuit 3 Amplifier B output
No internal connection
Circuit 3 Amplifier C output
Circuit 1 Amplifier C inverting input
Circuit 1 Amplifier B non-inverting input
Circuit 4 Negative power supply
Circuit 1 Amplifier D non-inverting input
Circuit 1 Amplifier D inverting input
Circuit 3 Amplifier D output
Circuit 2
Amplifier A enable pin internal pull-down; Logic “1” selects the disabled state;
Logic “0” selects the enabled state.
Circuit 2
Amplifier B enable pin with internal pull-down; Logic “1” selects the disabled
state; Logic “0” selects the enabled state.
IN-
CIRCUIT 1
V₊
IN+
V_-
V₊
LOGIC
PIN
V_-
CIRCUIT 2
V₊
OUT
V_-
CIRCUIT 3
V₊
CAPACITIVELY
COUPLED
ESD CLAMP
V_-
CIRCUIT 4
Applications Information
Introduction
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.
Rail-to-Rail Input
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
undesired change in magnitude and polarity of input offset
current.
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
100mV below the negative rail and 10% higher than the V₊
rail (0.5V higher than V₊ when V₊ equals 5V).
Input Protection
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.
10
FN6145.2
July 11, 2007