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PDF ISL28278 Data sheet ( Hoja de datos )
| Número de pieza | ISL28278 | |
| Descripción | (ISL28278 / ISL28478) Dual Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Precision Op-Amp | |
| Fabricantes | Intersil Corporation | |
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Data Sheet
ISL28278, ISL28478
September 28, 2006
FN6145.1
Dual Micropower Single Supply
Rail-to-Rail Input and Output (RRIO)
Precision Op-Amp
The ISL28278 and ISL28478 are Dual and Quad channel
micropower precision operational amplifier optimized for
single supply operation at 5V and can operate down to 2.4V.
For equivalent performance in a single channel op-amp
reference EL8178.
The ISL28278 and ISL28478 feature an Input Range
Enhancement Circuit (IREC) which enables both parts to
maintain CMRR performance for input voltages equal to the
positive and negative supply rails. The input signal is
capable of swinging 10% above the positive supply rail and
to 100mV below the negative supply with only a slight
degradation of the CMRR performance. The output
operation is rail to rail.
The both parts draw minimal supply current while meeting
excellent DC-accuracy, AC-performance, noise and output
drive specifications.
The ISL28278 and ISL28478 can be operated from one
lithium cell or two Ni-Cd batteries. The input range includes
bothwww.DataSheet4U.com positive and negative rail.
Ordering Information
PART TAPE &
PKG.
PART NUMBER MARKING REEL PACKAGE DWG. #
ISL28278FAZ
(See Note)
28278FAZ 97/Tube 16 Ld QSOP MDP0040
(Pb-free)
ISL28278FAZ-T7 28278FAZ
7” 16 Ld QSOP MDP0040
(See Note)
(1000 pcs) (Pb-free)
Coming Soon
ISL28478FAZ
(Note)
28478FAZ 97/Tube 16 Ld QSOP MDP0040
(Pb-free)
Coming Soon 28478FAZ
7” 16 Ld QSOP MDP0040
ISL28478FAZ-T7
(1000 pcs) (Pb-free)
(Note)
NOTE: Intersil Pb-free plus anneal products employ special Pb-free
material sets; molding compounds/die attach materials and 100%
matte tin plate termination finish, which are RoHS compliant and
compatible with both SnPb and Pb-free soldering operations. Intersil
Pb-free products are MSL classified at Pb-free peak reflow
temperatures that meet or exceed the Pb-free requirements of
IPC/JEDEC J STD-020.
Features
• Low Power 120µA typ supply current for both channels
• 225µV max offset voltage
• 30pA typ input bias current
• 300kHz gain-bandwidth product
• 100dB typ PSRR and CMRR
• Single supply operation down to 2.4V
• Input is capable of swinging above V+ and below V-
(ground sensing)
• Rail-to-rail input and output (RRIO)
• Pb-free plus anneal available (RoHS compliant)
Applications
• Battery- or solar-powered systems
• 4mA to 25mA current loops
• Handheld consumer products
• Medical devices
• Thermocouple amplifiers
• Photodiode pre-amps
• pH probe amplifiers
1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
1 page  
ISL28278, ISL28478
Typical Performance Curves (Continued)
120 80
80 40
40 0
0 -40
-40 -80
-80
1
-120
10 100 1k 10k 100k 1M 10M
FREQUENCY (Hz)
FIGURE 5. AVOL vs FREQUENCY @ 100kΩ LOAD
100
80
60
40
20
0
-20
10
PHASE
GAIN
100 1k 10k 100k
FREQUENCY (Hz)
200
150
100
50
0
-50
-100
-150
1M
FIGURE 6. AVOL vs FREQUENCY @ 1kΩ LOAD
10
0 VS = 5VDC
VSOURCE = 1Vp-p
-10 RL = 10kΩ
-20 AV = +1
-30
-40 PSRR -
-50
-60
-70
-80
-90
-100
10
100 1k
10k
PSRR (dB)
PSRR +
100k
FIGURE 7. PSRR vs FREQUENCY
1M
10
0 VS = ±2.5VDC
-10 VSOURCE = 1Vp-p
-20 RL = 10kΩ
-30
-40
-50
-60
-70
-80
-90
-100
10
100 1k
10k 100k
TEMPERATURE (°C)
FIGURE 8. CMRR vs FREQUENCY
1M
2.56
2.54
VIN
2.52
2.50
VOUT
2.48
2.46
2.44
VS = 5VDC
VOUT = 0.1Vp-p
RL = 1kΩ
AV = +1
2.42
0 2 4 6 8 10 12 14 16 18 20
TIME (µs)
FIGURE 9. SMALL SIGNAL TRANSIENT RESPONSE
5.0
VS = 5VDC
4.0
VOUT = 2Vp-p
RL = 1kΩ
VOUT
AV = -2
3.0
2.0
1.0 VIN
0
0 50 100 150 200 250
TIME (µs)
FIGURE 10. LARGE SIGNAL TRANSIENT RESPONSE
5 FN6145.1
September 28, 2006
5 Page 
ISL28278, ISL28478
Applications Information
Introduction
The ISL28278 and ISL28478 are Dual and Quad channel
CMOS rail-to-rail input, output (RRIO) micropower precision
operational amplifier with an enable feature. The parts are
designed to operate from single supply (2.4V to 5.0V) or dual
supply (±1.2V to ±2.5V) while drawing only 120μA of supply
current. The device has an input common mode range that
extends 10% above the positive rail and up to 100mV below
the negative supply rail. The output operation can swing
within about 4mV of the supply rails with a 100kΩ load
(reference Figures 27 through 30). This combination of low
power and precision performance makes them suitable for
solar and battery power applications.
Rail-to-Rail Input
The input common-mode voltage range of the ISL28278 and
ISL28478 is from the negative supply to 10% greater than
the positive supply without introducing additional offset
errors or degrading performance associated with a
conventional rail-to-rail input operational amplifier. 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 and ISL28487 achieve input rail-to-rail
operation 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
both positive and negative supply rails, limiting the input
voltage to within one diode beyond the supply rails. They
have additional 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.
Rail-to-Rail Output
A pair of complementary MOSFET devices are used to
achieve the rail-to-rail output swing. The NMOS sinks
current to swing the output in the negative direction. The
PMOS sources current to swing the output in the positive
direction. The ISL28278 and ISL28478 with a 100kΩ load
will swing to within 4mV of the positive supply rail and within
3mV of the negative supply rail.
Enable/Disable Feature
The ISL28278 has an EN pin that disables the device when
pulled up to at least 2.0V. In the disabled state (output in a
high impedance state), the part consumes typically 4µA. By
disabling the part, multiple ISL28278 parts can be connected
together as a MUX. In this configuration, the outputs are tied
together in parallel and a channel can be selected by the EN
pin. The EN pin also has an internal pull down. If left open,
the EN pin will pull to the negative rail and the device will be
enabled by default.
The loading effects of the feedback resistors of the disabled
amplifier must be considered when multiple amplifier outputs
are connected together.
Using Only One Channel
The ISL28278 and ISL28478 are Dual and Quad channel
opamps. If the application only requires one channel when
using the ISL28278 or less than 4 channels when using the
ISL28478, the user must configure the unused channel (s) to
prevent them from oscillating. The unused channel (s) 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
negative input and ground the positive input (as shown in
Figure 37).
-
+ 1/2 ISL28278
1/4 ISL28478
FIGURE 37. PREVENTING OSCILLATIONS IN UNUSED
CHANNELS
Proper Layout Maximizes Performance
To achieve the maximum performance of the high input
impedance and low offset voltage, care should be taken in
the circuit board layout. The PC board surface must remain
clean and free of moisture to avoid leakage currents
between adjacent traces. Surface coating of the circuit board
will reduce surface moisture and provide a humidity barrier,
reducing parasitic resistance on the board. When input
leakage current is a concern, the use of guard rings around
the amplifier inputs will further reduce leakage currents.
Figure 38 shows a guard ring example for a unity gain
amplifier that uses the low impedance amplifier output at the
same voltage as the high impedance input to eliminate
surface leakage. The guard ring does not need to be a
specific width, but it should form a continuous loop around
both inputs. For further reduction of leakage currents,
11 FN6145.1
September 28, 2006
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet ISL28278.PDF ] | |
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