INTERSIL ISL28288

ISL28288
®
Data Sheet
September 20, 2006
Dual Micropower Single Supply
Rail-to-Rail Input and Output (RRIO)
Precision Op-Amp
FN6339.0
Features
• Low power 120µA typ supply current for both channels
The ISL28288 is a dual 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 EL8188.
The ISL28288 features an Input Range Enhancement Circuit
(IREC) which enables the ISL28288 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 ISL28288 draws minimal supply current while meeting
excellent DC-accuracy, AC-performance, noise and output
drive specifications.
The ISL28288 can be operated from one lithium cell or two
Ni-Cd batteries. The input range includes both positive and
negative rail.
• 1.5mV 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
Ordering Information
• Photodiode pre-amps
PART
PART NUMBER MARKING
TAPE &
REEL
ISL28288FUZ
(See Note)
50/Tube
28288Z
ISL28288FUZ-T7 28288Z
(See Note)
PACKAGE
PKG.
DWG. #
10 Ld MSOP MDP0043
(Pb-free)
• pH probe amplifiers
Pinout
ISL28288
(10 LD MSOP)
TOP VIEW
7”
10 Ld MSOP MDP0043
(1500 pcs) (Pb-free)
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.
IN+_A 1
EN_A 2
V- 3
EN_B 4
IN+_B 5
1
10 IN-_A
+
9 OUT_A
8 V+
+
-
7 OUT_B
6 IN-_B
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.
ISL28288
Absolute Maximum Ratings (TA = +25°C)
Output Short-Circuit Duration . . . . . . . . . . . . . . . . . . . . . . .Indefinite
Ambient Operating Temperature Range . . . . . . . . .-40°C to +125°C
Storage Temperature Range . . . . . . . . . . . . . . . . . .-65°C to +150°C
Operating Junction Temperature . . . . . . . . . . . . . . . . . . . . . +125°C
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5V
Supply Turn On Voltage Slew Rate . . . . . . . . . . . . . . . . . . . . . 1V/µs
Differential Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5V
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . V- - 0.5V to V+ + 0.5V
ESD tolerance, Human Body Model . . . . . . . . . . . . . . . . . . . . . .3kV
ESD tolerance, Machine Model . . . . . . . . . . . . . . . . . . . . . . . . .300V
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests
are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
Operating Junction
Electrical Specifications
PARAMETER
V+ = 5V, V- = 0V, VCM = 2.5V, VO = 1.4V, TA = +25°C unless otherwise specified.
Boldface limits apply over the operating temperature range, -40°C to +125°C, temperature data
guaranteed by characterization
DESCRIPTION
CONDITIONS
MIN
TYP
MAX
UNIT
-1.5
-2
±0.05
1.5
2
mV
VOS
Input Offset Voltage
∆V OS
-----------------∆Time
Long Term Input Offset Voltage Stability
1.2
µV/Mo
∆V OS
---------------∆T
Input Offset Drift vs Temperature
2.2
µV/°C
IOS
Input Offset Current
±5
30
600
pA
±10
30
80
pA
-600
IB
Input Bias Current
-40°C to +85°C
eN
-30
-80
Input Noise Voltage Peak-to-Peak
f = 0.1Hz to 10Hz
5.4
µVPP
Input Noise Voltage Density
fO = 1kHz
48
nV/√Hz
iN
Input Noise Current Density
fO = 1kHz
0.1
pA/√Hz
CMIR
Input Voltage Range
Guaranteed by CMRR test
0
CMRR
Common-Mode Rejection Ratio
VCM = 0V to 5V
80
75
100
dB
PSRR
Power Supply Rejection Ratio
V+ = 2.4V to 5V
85
80
105
dB
AVOL
Large Signal Voltage Gain
VO = 0.5V to 4.5V, RL = 100kΩ
200
190
300
V/mV
VO = 0.5V to 4.5V, RL = 1kΩ
25
V/mV
Output low, RL = 100kΩ
3
6
30
mV
130
175
225
mV
VOUT
Maximum Output Voltage Swing
Output low, RL = 1kΩ
SR
Slew Rate
GBW
Gain Bandwidth Product
2
5
V
Output high, RL = 100kΩ
4.990
4.97
4.996
V
Output high, RL = 1kΩ
4.800
4.750
4.880
V
0.12
0.09
±0.14
300
0.16
0.21
V/µs
kHz
FN6339.0
September 20, 2006
ISL28288
Electrical Specifications
PARAMETER
V+ = 5V, V- = 0V, VCM = 2.5V, VO = 1.4V, TA = +25°C unless otherwise specified.
Boldface limits apply over the operating temperature range, -40°C to +125°C, temperature data
guaranteed by characterization (Continued)
DESCRIPTION
CONDITIONS
MIN
TYP
MAX
UNIT
IS,ON
Supply Current, Enabled
All channels enabled.
120
156
175
µA
IS,OFF
Supply Current, Disabled
All channels disabled.
4
7
9
µA
ISC+
Short Circuit Sourcing Capability
RL = 10Ω
29
24
31
mA
ISC-
Short Circuit Sinking Capability
RL = 10Ω
24
20
26
mA
VS
Minimum Supply Voltage
VINH
Enable Pin High Level
VINL
Enable Pin Low Level
IENH
Enable Pin Input Current
VEN = 5V
IENL
Enable Pin Input Current
VEN = 0V
2.4
V
2
V
-0.1
0.8
V
0.8
1
1.5
µA
0
+0.1
µA
Typical Performance Curves
+1
45
0
-2
GAIN (dB)
35
VS = ±1.2V
RL = 10k
VS = ±2.5V
RL = 10k
-3
-4
30
GAIN (dB)
-1
40
VS = ±1.2V
RL = 1k
VS = ±2.5V
RL = 1k
-5 Vout = 50mVp-p
AV = 1
-6 C = 3pF
L
RF=0/RG = INF
-7
8
1k
10k
100k
FREQUENCY (Hz)
1M
VS = ±1.2V
20
AV = 100
15 RL = 10kΩ
CL = 3pF
10 R = 100kΩ
F
RG = 1kΩ
5
0
100
5M
VS = ±1.0V
1k
10k
100k
1M
FREQUENCY (Hz)
FIGURE 1. FREQUENCY RESPONSE vs SUPPLY VOLTAGE
FIGURE 2. FREQUENCY RESPONSE vs SUPPLY VOLTAGE
0
80
INPUT OFFSET VOLTAGE (µV)
100
INPUT OFFSET VOLTAGE (µV)
VS = ±2.5V
25
VCM = VDD/2
60
40
20
VDD = 5V
0
-20
-40
VDD = 2.5V
-60
-80
-100
0
1
2
3
4
5
OUTPUT VOLTAGE (V)
FIGURE 3. INPUT OFFSET VOLTAGE vs OUTPUT VOLTAGE
3
-20
VOS, µV
-40
-60
-80
-100
0
1
2
3
4
5
COMMON-MODE INPUT VOLTAGE (V)
FIGURE 4. INPUT OFFSET VOLTAGE vs COMMON-MODE
INPUT VOLTAGE
FN6339.0
September 20, 2006
ISL28288
(Continued)
100
80
40
80
40
0
-80
1
10
100
10k
1k
100k
50
40
0
20
-20
10
GAIN
-50
-100
100
1k
10k
-150
1M
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
FIGURE 5. AVOL vs FREQUENCY @ 100kΩ LOAD
FIGURE 6. AVOL vs FREQUENCY @ 1kΩ LOAD
10
10
VS = 5VDC
VSOURCE = 1Vp-p
RL = 10kΩ
AV = +1
-10
-20
0
-20
-30
PSRR -
-40
-50
-60
PSRR +
-30
-40
-50
-60
-70
-70
-80
-80
-90
-90
-100
-100
10
100
VS = ±2.5VDC
VSOURCE = 1Vp-p
RL = 10kΩ
-10
CMRR (dB)
TEMPERATURE (°C)
0
1k
10k
100k
1M
10
100
PSRR (dB)
1k
10k
100k
1M
TEMPERATURE (°C)
FIGURE 7. PSRR vs FREQUENCY
FIGURE 8. CMRR vs FREQUENCY
5.0
2.56
VS = 5VDC
VOUT = 2Vp-p
RL = 1kΩ
AV = -2
VIN
2.54
4.0
2.52
VOLTS (V)
2.50
2.48
VS = 5VDC
VOUT = 0.1Vp-p
RL = 1kΩ
AV = +1
2.46
2.44
2
4
6
8
10
12
14
16
18
20
TIME (µs)
FIGURE 9. SMALL SIGNAL TRANSIENT RESPONSE
4
2.0
VIN
1.0
0
2.42
0
VOUT
3.0
VOUT
VOLTS (V)
100
0
-120
10M
1M
150
60
-80
-40
200
PHASE
GAIN (dB)
-40
0
PHASE (°)
80
GAIN (dB)
120
PHASE (°)
Typical Performance Curves
0
50
100
150
200
250
TIME (µs)
FIGURE 10. LARGE SIGNAL TRANSIENT RESPONSE
FN6339.0
September 20, 2006
ISL28288
Typical Performance Curves
(Continued)
1k
VOLTAGE NOISE (nV/√Hz)
CURRENT NOISE (pA/√Hz)
10.00
1.00
0.10
100
10
0.01
1
10
100
1k
1
100k
10k
1
10
1k
100
FREQUENCY (Hz)
FIGURE 11. CURRENT NOISE vs FREQUENCY
100k
FIGURE 12. VOLTAGE NOISE vs FREQUENCY
6
V+ = 5V
VIN
5
VOLTS (V)
VOLTAGE NOISE (1µV/DIV)
10k
FREQUENCY (Hz)
4
100K
VS +
100K
3
DUT
+
1K
VOUT
VS -
Function
Generator
33140A
2
1
5.4µVP-P
0
0
50
TIME (1s/DIV)
100
150
200
TIME (ms)
FIGURE 13. 0.1Hz TO 10Hz INPUT VOLTAGE NOISE
FIGURE 14. INPUT VOLTAGE SWING ABOVE THE V+ SUPPLY
AV = -1
VIN = 200mVp-p
V+ = 5V
V- = 0V
EN
Input
1V/DIV
135
115
95
75
0
55
35
2
2.5
3
3.5
4
4.5
5
5.5
SUPPLY VOLTAGE (V)
FIGURE 15. SUPPLY CURRENT vs SUPPLY VOLTAGE
5
VOUT
0.1V/DIV
SUPPLY CURRENT (µA)
155
0
10µs/DIV
FIGURE 16. ENABLE TO OUTPUT DELAY TIME
FN6339.0
September 20, 2006
ISL28288
Typical Performance Curves
(Continued)
4.8
160
n = 12
n = 12
4.6
150
CURRENT (uA)
CURRENT (uA)
MAX
140
MEDIAN
130
120
110
MAX
4.2
MEDIAN
4
3.8
3.6
MIN
100
90
-40
4.4
MIN
3.4
3.2
-20
0
20
40
60
80
100
120
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
FIGURE 17. SUPPLY CURRENT vs TEMPERATURE
VS = ±2.5V ENABLED, RL = INF
50
0
0
-100
CURRENT (pA)
CURRENT (pA)
n = 12
-200
MAX
-300
-400
-100
MAX
-150
-200
MEDIAN
-250
MIN
-300
-20
0
20
40
60
80
TEMPERATURE (°C)
100
-350
-40
120
FIGURE 19. I BIAS(+) vs TEMPERATURE VS = ±2.5V
450.05
MAX
0
0
n = 12
20
40
60
80
TEMPERATURE (°C)
100
120
MAX
400.05
350.05
Min
MIN
AVOL(V/mV)
n = 12
MEDIAN
-20
FIGURE 20. I BIAS(-) vs TEMPERATURE VS = ±2.5V
50
CURRENT (pA)
n = 12
MIN
-600
-100
-150
-200
-250
300.05
250.05
200.05
MEDIAN
MIN
150.05
100.05
-300
-350
-40
-50
MEDIAN
-500
-50
120
FIGURE 18. SUPPLY CURRENT vs TEMPERATURE
VS = ±2.5V DISABLED, RL = INF
100
-700
-40
100
50.05
-20
0
20
40
60
80
TEMPERATURE (°C)
100
120
FIGURE 21. INPUT OFFSET CURRENT vs TEMPERATURE
VS = ±2.5V
6
0.05
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
100
120
FIGURE 22. AVOL vs TEMPERATURE RL =100k, VO @ +2V/-2V
@ VS ±2.5V
FN6339.0
September 20, 2006
ISL28288
Typical Performance Curves
800
(Continued)
800
n = 12
MAX
600
400
MAX
400
VOLTAGE (µV)
VOLTAGE (µV)
n = 12
600
200
0
-200
MEDIAN
-400
-600
200
0
-200
MEDIAN
-400
-600
MIN
-800
-1000
-40
MIN
-800
-1000
-20
0
20
40
60
80
100
120
-40
-20
0
TEMPERATURE (°C)
60
80
100
120
FIGURE 24. INPUT OFFSET VOLTAGE vs TEMPERATURE
VS = ±1.2V
140
140
n = 12
n = 12
130
130
120
MAX
PSRR (dB)
CMRR (dB)
40
TEMPERATURE (°C)
FIGURE 23. INPUT OFFSET VOLTAGE vs TEMPERATURE
VS = ±2.5V
110
80
-40
0
20
40
60
80
TEMPERATURE (°C)
100
4.89
110
MEDIAN
80
-40
120
MIN
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 25. CMRR vs TEMPERATURE, FREQ = 0Hz,
VCM = +2.5V TO -2.5V
4.895
MAX
90
MIN
-20
120
100
100 MEDIAN
90
FIGURE 26. PSRR vs TEMPERATURE, FREQ = 0Hz,
VS = ±1.2V TO ±2.5V
180
n = 12
n = 12
170
4.885
MAX
160
4.88
MAX
4.875
VOUT (mV)
VOUT (V)
20
4.87
4.865 MEDIAN
4.86
150
140
MEDIAN
130
MIN
MIN
120
4.855
4.85
110
4.845
4.84
-40
100
-20
0
20
40
60
80
TEMPERATURE (°C)
100
120
FIGURE 27. POSITIVE VOUT vs TEMPERATURE RL = 1k,
VS = ±2.5V
7
-40
-20
0
20
40
60
80
100
120
TEMPERATURE (°C)
FIGURE 28. NEGATIVE VOUT vs TEMPERATURE RL = 1k,
VS = ±2.5V
FN6339.0
September 20, 2006
ISL28288
Typical Performance Curves
(Continued)
4.3
4.9984
4.2
MAX
4.998
4.1
VOUT (mV)
VOUT (V)
4.9978
4.9976
4.9974
4.9972
n = 12
n = 12
4.9982
MEDIAN
MIN
4.997
4
MAX
MEDIAN
3.9
3.8
3.7
4.9968
3.6
4.9966
3.5
MIN
3.4
4.9964
-40
-20
0
20
40
60
80 100
TEMPERATURE (°C)
-40
120
FIGURE 29. POSITIVE VOUT vs TEMPERATURE RL = 100k,
VS = ±2.5V
-20
20
40
60
80 100
TEMPERATURE (°C)
120
FIGURE 30. NEGATIVE VOUT vs TEMPERATURE RL = 100k,
VS = ±2.5V
0.9
14.5
0
n = 12
n = 12
MAX
0.85
14
CURRENT (µA)
CURRENT (nA)
MAX
13.5
13
12.5
MEDIAN
MIN
12
-20
0
20
40
60
80
TEMPERATURE (°C)
100
0
20
40
60
80
TEMPERATURE (°C)
100
120
0.2
0.19
SLEW RATE (V/µs))
SLEW RATE (V/µs)
-20
FIGURE 32. IIH (EN) vs TEMPERATURE VS = ±2.5V
n = 12
0.18
MAX
0.17
0.16
MEDIAN
0.14
0.13
0.12
MIN
0.16
0.15
0.13
0.11
20
40
60
80
TEMPERATURE (°C)
100
120
FIGURE 33. +SLEW RATE vs TEMPERATURE VS = ±2.5V,
INPUT = ±0.75V AV = 2
8
MEDIAN
0.14
0.12
0
MAX
0.17
0.1
-20
n = 12
0.18
0.11
0.09
-40
MIN
0.7
0.55
-40
120
0.2
0.15
MEDIAN
0.6
FIGURE 31. IIL (EN) vs TEMPERATURE VS = ±2.5V
0.19
0.75
0.65
11.5
11
-40
0.8
0.1
-40
MIN
-20
0
20
40
60
80
TEMPERATURE (°C)
100
120
FIGURE 34. -SLEW RATE vs TEMPERATURE VS = ±2.5V,
INPUT = ±0.75V AV = 2
FN6339.0
September 20, 2006
ISL28288
Typical Performance Curves
(Continued)
JEDEC JESD51-3 LOW EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD
1.4
1.2
1.2
1
POWER DISSIPATION (W)
POWER DISSIPATION (W)
JEDEC JESD51-7 HIGH EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD
893mW
1
QS
θ
OP
JA
16
=1
12
°C
/W
0.8
0.6
0.4
0.2
0.8
633mW
0.6
θJ
0.4
QS
O
A =1
58
P1
°C
6
/W
0.2
0
0
0
25
50
75 85
100
125
0
150
25
50
75 85 100
125
150
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
FIGURE 35. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
FIGURE 36. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
Pin Descriptions
ISL28288
(10 LD MSOP)
PIN NAME
EQUIVALENT
CIRCUIT
1
IN+_A
Circuit 1
Amplifier A non-inverting input
2
EN_A
Circuit 2
Amplifier A enable pin internal pull-down; Logic “1” selects the disabled state; Logic “0” selects the
enabled state.
3
V-
Circuit 4
Negative power supply
4
EN_B
Circuit 2
Amplifier B enable pin with internal pull-down; Logic “1” selects the disabled state; Logic “0”
selects the enabled state.
5
IN+_B
Circuit 1
Amplifier B non-inverting input
6
IN-_B
Circuit 1
Amplifier B inverting input
7
OUT_B
Circuit 3
Amplifier B output
8
V+
Circuit 4
Positive power supply
9
OUT_A
Circuit 3
Amplifier A output
10
IN-_A
Circuit 1
Amplifier A inverting input
DESCRIPTION
V+
V+
IN-
V+
IN+
LOGIC
PIN
V-
VCIRCUIT 2
9
CAPACITIVELY
COUPLED
ESD CLAMP
OUT
V-
CIRCUIT 1
V+
VCIRCUIT 3
CIRCUIT 4
FN6339.0
September 20, 2006
ISL28288
Applications Information
Introduction
The ISL28288 is a dual CMOS rail-to-rail input, output
(RRIO) micropower precision operational amplifier with an
enable feature. The part is 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 this device suitable for solar and battery
power applications.
Rail-to-Rail Input
The input common-mode voltage range of the ISL28288
goes from negative supply to 10% greater than the positive
supply without introducing additional offset errors or
degrading performance associated with a conventional railto-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 ISL28288 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
both positive and negative supply rails, limiting the input
voltage to within one diode beyond the supply rails. The
ISL28288 has 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
Enable/Disable Feature
The ISL28288 offers 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 ISL28288 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 ISL28288 is a dual opamp. If the application only
requires one channel, 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 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).
ISL28288
+
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 of the ISL28288, 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
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 ISL28288 with a 100kΩ load will swing to
within 4mV of the positive supply rail and within 3mV of the
negative supply rail.
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ISL28288
currents, components can be mounted to the PC board
using Teflon standoff insulators.
V+
HIGH IMPEDANCE INPUT
1/2 ISL28288
IN
Current Limiting
The ISL28288 has no internal current-limiting circuitry. If the
output is shorted, it is possible to exceed the Absolute
Maximum Rating for output current or power dissipation,
potentially resulting in the destruction of the device.
Power Dissipation
FIGURE 38. GUARD RING EXAMPLE FOR UNITY GAIN
AMPLIFIER
Example Application
Thermocouples are the most popular temperature-sensing
device because of their low cost, interchangeability, and
ability to measure a wide range of temperatures. The
ISL28288 (Figure 39) is used to convert the differential
thermocouple voltage into single-ended signal with 10X gain.
The ISL28288's rail-to-rail input characteristic allows the
thermocouple to be biased at ground and the amplifier to run
from a single 5V supply.
R4
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 (TJMAX) 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 as follows:
T JMAX = T MAX + ( θ JA xPD MAXTOTAL )
(EQ. 1)
where:
• PDMAXTOTAL is the sum of the maximum power
dissipation of each amplifier in the package (PDMAX)
• PDMAX for each amplifier can be calculated as follows:
V OUTMAX
PD MAX = 2*V S × I SMAX + ( V S - V OUTMAX ) × ---------------------------R
L
(EQ. 2)
100kΩ
R3
10kΩ
R2
K TYPE
THERMOCOUPLE
10kΩ
V+
+
ISL28288
V-
where:
410µV/°C
+
5V
R1
100kΩ
FIGURE 39. THERMOCOUPLE AMPLIFIER
• TMAX = Maximum ambient temperature
• θJA = Thermal resistance of the package
• PDMAX = Maximum power dissipation of 1 amplifier
• VS = Supply voltage
• IMAX = Maximum supply current of 1 amplifier
• VOUTMAX = Maximum output voltage swing of the
application
• RL = Load resistance
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ISL28288
Mini SO Package Family (MSOP)
0.25 M C A B
D
MINI SO PACKAGE FAMILY
(N/2)+1
N
E
MDP0043
A
E1
PIN #1
I.D.
1
B
(N/2)
e
H
C
SEATING
PLANE
SYMBOL
MSOP8
MSOP10
TOLERANCE
NOTES
A
1.10
1.10
Max.
-
A1
0.10
0.10
±0.05
-
A2
0.86
0.86
±0.09
-
b
0.33
0.23
+0.07/-0.08
-
c
0.18
0.18
±0.05
-
D
3.00
3.00
±0.10
1, 3
E
4.90
4.90
±0.15
-
E1
3.00
3.00
±0.10
2, 3
e
0.65
0.50
Basic
-
L
0.55
0.55
±0.15
-
L1
0.95
0.95
Basic
-
N
8
10
Reference
Rev. C 6/99
0.10 C
N LEADS
0.08 M C A B
b
NOTES:
1. Plastic or metal protrusions of 0.15mm maximum per side are not
included.
2. Plastic interlead protrusions of 0.25mm maximum per side are
not included.
L1
3. Dimensions “D” and “E1” are measured at Datum Plane “H”.
A
4. Dimensioning and tolerancing per ASME Y14.5M-1994.
c
SEE DETAIL "X"
A2
GAUGE
PLANE
A1
L
0.25
3° ±3°
DETAIL X
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