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ISL28288, ISL28488
Data Sheet June 28, 2007 FN6339.1
Dual and Quad Micropower Single Supply Rail-to-Rail Input and Output (RRIO) Op-Amp
The ISL28288 and ISL28488 are dual and quad channel micropower operational amplifiers optimized for single supply operation over the 2.4V to 5V range. They can be operated from one lithium cell or two Ni-Cd batteries. For equivalent performance in a single channel op-amp reference EL8188. These devices feature an Input Range Enhancement Circuit (IREC) which enables them to maintain CMRR performance for input voltages 10% above the positive supply rail and to 100mV below the negative supply. The output operation is rail to rail. The ISL28288 and ISL28488 draw minimal supply current while meeting excellent DC-accuracy, AC-performance, noise and output drive specifications. The ISL28288 contains a power down enable pin that reduces the power supply current to typically less than 4A in the disabled state.
Features
* Low power 120A typical supply current * 1.5mV max offset voltage * 30pA max input bias current * 300kHz typical gain-bandwidth product * 105dB typical PSRR * 100dB typical 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) * Enable Pin (ISL28288 only) * Pb-free plus anneal available (RoHS compliant)
Applications
* Battery- or solar-powered systems * 4mA to 25mA current loops
Pinouts
ISL28288 (10 LD MSOP) TOP VIEW
IN+_A 1 EN_A 2 V- 3 EN_B 4 IN+_B 5 + + 10 IN-_A 9 OUT_A 8 V+ 7 OUT_B 6 IN-_B
* Handheld consumer products * Medical devices * Thermocouple amplifiers * Photodiode pre-amps * pH probe amplifiers
Ordering Information
PART NUMBER (Note) ISL28288FUZ PART MARKING 8288Z 8288Z 28488 FAZ 28488 FAZ PACKAGE (Pb-Free) 10 Ld MSOP 10 Ld MSOP 16 Ld QSOP 16 Ld QSOP PKG. DWG. # MDP0043 MDP0043 MDP0040 MDP0040
ISL28488 (16 LD QSOP) TOP VIEW
OUT_A 1 IN-_A 2 + IN+_A 3 V+ 4 IN+_B 5 IN-_B 6 OUT_B 7 NC 8 + + + 16 OUT_D 15 IN-_D 14 IN+_D 13 V12 IN+_C 11 IN-_C 10 OUT_C 9 NC
ISL28288FUZ-T7 ISL28488FAZ ISL28488FAZ-T7
*"-T7" suffix is for tape and reel. Please refer to TB347 for details on reel specifications. 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.
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, 2007. All Rights Reserved All other trademarks mentioned are the property of their respective owners.
ISL28288, ISL28488
Absolute Maximum Ratings (TA = +25C)
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5V Supply Turn On Voltage Slew Rate . . . . . . . . . . . . . . . . . . . . . 1V/s Differential Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5V Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . V- - 0.5V to V+ + 0.5V ESD Tolerance Human Body Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3kV Machine Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .300V
Thermal Information
Thermal Resistance JA (C/W) 10 Ld MSOP Package . . . . . . . . . . . . . . . . . . . . . . . 115 16 Ld QSOP Package . . . . . . . . . . . . . . . . . . . . . . . 112 Output Short-Circuit Duration . . . . . . . . . . . . . . . . . . . . . . .Indefinite Ambient Operating Temperature Range . . . . . . . . .-40C to +125C Storage Temperature Range . . . . . . . . . . . . . . . . . .-65C to +150C Operating Junction Temperature . . . . . . . . . . . . . . . . . . . . . +125C Pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . .see link below http://www.intersil.com/pbfree/Pb-FreeReflow.asp
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and result in failures not covered by warranty. 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
V+ = 5V, V- = 0V, VCM = 2.5V, RL = Open, TA = +25C unless otherwise specified. Boldface limits apply over the operating temperature range, -40C to +125C. Temperature data established by characterization CONDITIONS MIN (Note 1) TYP MAX (Note 1) UNIT
PARAMETER DC SPECIFICATIONS VOS V OS -----------------Time V OS --------------T IOS IB CMIR CMRR PSRR AVOL
DESCRIPTION
Input Offset Voltage Long Term Input Offset Voltage Stability Input Offset Voltage vs Temperature Input Offset Current -40C to +85C Input Bias Current -40C to +85C Common-Mode Voltage Range Common-Mode Rejection Ratio Power Supply Rejection Ratio Large Signal Voltage Gain Guaranteed by CMRR VCM = 0V to 5V V+ = 2.4V to 5V VO = 0.5V to 4.5V, RL = 100k VO = 0.5V to 4.5V, RL = 1k ISL28288
-1.5 -2
0.05
1.5 2
mV V/Mo V/C
1.2 0.9 -30 -80 -30 -80 0 80 75 85 80 200 190 100 105 300 60 3 130 4.990 4.97 4.800 4.750 4.996 4.880 120 240 156 175 315 350 6 30 175 225
5
30 80 30 80 5
pA pA V dB dB V/mV V/mV mV mV V V A A
10
VOUT
Maximum Output Voltage Swing
Output low, RL = 100k Output low, RL = 1k Output high, RL = 100k Output high, RL = 1k
IS,ON
Quiescent Supply Current, Enabled
ISL28288, All channels enabled. ISL28488, All channels enabled.
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FN6339.1 June 28, 2007
ISL28288, ISL28488
Electrical Specifications
V+ = 5V, V- = 0V, VCM = 2.5V, RL = Open, TA = +25C unless otherwise specified. Boldface limits apply over the operating temperature range, -40C to +125C. Temperature data established by characterization (Continued) CONDITIONS All channels disabled. RL = 10 RL = 10 V+ to V29 24 24 20 2.4 2 0.8 VEN = V+ VEN = V0.8 0 1 1.5 +0.1 MIN (Note 1) TYP 4 31 26 5.0 MAX (Note 1) 7 9 UNIT A mA mA V V V A A
PARAMETER IS,OFF IO+ IOVSUPPLY VENH VENL IENH IENL
DESCRIPTION Quiescent Supply Current, Disabled (ISL28288) Short Circuit Sourcing Capability Short Circuit Sinking Capability Supply Operating Range EN Pin High Level (ISL28288) EN Pin Low Level (ISL28288) EN Pin Input High Current (ISL28288) EN Pin Input Low Current (ISL28288)
AC SPECIFICATIONS GBW en Gain Bandwidth Product Input Noise Voltage Peak-to-Peak Input Noise Voltage Density in CMRR @ 60Hz PSRR+ @ 120Hz PSRR- @ 120Hz Input Noise Current Density Input Common Mode Rejection Ratio Power Supply Rejection Ratio (V+) Power Supply Rejection Ratio (V-) AV = 100, RF = 100k, RG = 1k, RL = 10k to VCM f = 0.1Hz to 10Hz fO = 1kHz fO = 1kHz VCM = 1VP-P, RL = 10k to VCM V+, V- = 1.2V and 2.5V, VSOURCE = 1VP-P, RL = 10k to VCM V+, V- = 1.2V and 2.5V VSOURCE = 1VP-P, RL = 10k to VCM 300 5.4 48 0.1 -70 -80 -60 kHz VP-P nV/Hz pA/Hz dB dB dB
TRANSIENT RESPONSE SR tEN Slew Rate Enable to Output Turn-on Delay Time, 10% EN to 10% Vout, (ISL28288) Enable to Output Turn-off Delay Time, 10% EN to 10% Vout, (ISL28288) NOTE: 1. Parts are 100% tested at +25C. Over temperature limits established by characterization and are not production tested. VEN = 5V to 0V, AV = -1, RG = RF = RL = 1k to VCM VEN = 0V to 5V, AV = -1, RG = RF = RL = 1k to VCM
0.12 0.09 0.14 0.16 0.21
V/s s s
2 0.1
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FN6339.1 June 28, 2007
ISL28288, ISL28488 Typical Performance Curves V+ = 5V, V- = 0V, VCM = 2.5V, RL = Open
+1 0 -1 -2 GAIN (dB) -3 -4 -5 VOUT = 50mVP-P AV = 1 -6 C = 3pF L RF = 0, RG = INF -7 8 1k 10k 100k FREQUENCY (Hz) 1M 5M V+, V- = 2.5V RL = 10k V+, V-= 2.5V RL = 1k V+, V- = 1.2V RL = 1k GAIN (dB) V+, V- = 1.2V RL = 10k 45 40 35 30 25 20 AV = 100 15 RL = 10k CL = 3pF 10 R = 100k F RG = 1k 5 0 100 1k V+, V- = 2.5V V+, V- = 1.2V
V+, V- = 1.0V
10k FREQUENCY (Hz)
100k
1M
FIGURE 1. FREQUENCY RESPONSE vs SUPPLY VOLTAGE
FIGURE 2. FREQUENCY RESPONSE vs SUPPLY VOLTAGE
120 80 GAIN (dB) 40 0 -40 -80 1 10 100 1k 10k 100k 1M FREQUENCY (Hz)
80 40 PHASE () GAIN (dB) 0 -40 -80 -120 10M
100 80 PHASE 60 40
200 150 100 50 0 PHASE ()
20 0 -20 10
GAIN
-50 -100 -150 1M
100
1k
10k
100k
FREQUENCY (Hz)
FIGURE 3. AVOL vs FREQUENCY @ 100k LOAD
FIGURE 4. AVOL vs FREQUENCY @ 1k LOAD
10 V+ = 5VDC VSOURCE = 1VP-P -10 R = 10k L -20 A = +1 V -30 PSRR -40 0 -50 -60 -70 -80 -90 -100 10 100 1k 10k 100k 1M PSRR +
10 0 -10 -20 CMRR (dB) -30 -40 -50 -60 -70 -80 -90 -100 10 100 1k 10k 100k 1M V+, V- = 2.5VDC VSOURCE = 1VP-P RL = 10k
PSRR (dB)
FREQUENCY (Hz)
FREQUENCY (Hz)
FIGURE 5. PSRR vs FREQUENCY
FIGURE 6. CMRR vs FREQUENCY
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FN6339.1 June 28, 2007
ISL28288, ISL28488 Typical Performance Curves V+ = 5V, V- = 0V, VCM = 2.5V, RL = Open
10.00 CURRENT NOISE (pA/Hz) VOLTAGE NOISE (nV/Hz)
(Continued)
1k
1.00
100
0.10
10
0.01 1 10 100 1k 10k 100k FREQUENCY (Hz)
1 1 10 100 1k 10k 100k FREQUENCY (Hz)
FIGURE 7. CURRENT NOISE vs FREQUENCY
FIGURE 8. VOLTAGE NOISE vs FREQUENCY
2.56 VIN 2.54 VOLTAGE NOISE (1V/DIV) 2.52 VOUT VOLTS (V) 2.50 2.48 2.46 V+ = 5VDC VOUT = 0.1VP-P RL = 1k AV = +1 0 TIME (1s/DIV) 2 4 6 8 10 12 14 16 18 20
5.4VP-P
2.44 2.42
TIME (s)
FIGURE 9. 0.1Hz TO 10Hz INPUT VOLTAGE NOISE
FIGURE 10. SMALL SIGNAL TRANSIENT RESPONSE
5.0 4.0 3.0 VOLTS (V) 2.0 1.0 0 0 50 100 150 200 250 VIN 0.1V/DIV 0 VOUT V+ = 5VDC VOUT = 2VP-P RL = 1k AV = -2 VOUT 1V/DIV EN INPUT AV = -1 VIN = 200mVP-P V+ = 5V V- = 0V
0 10s/DIV
TIME (s)
FIGURE 11. LARGE SIGNAL TRANSIENT RESPONSE
FIGURE 12. ENABLE TO OUTPUT DELAY TIME
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FN6339.1 June 28, 2007
ISL28288, ISL28488 Typical Performance Curves V+ = 5V, V- = 0V, VCM = 2.5V, RL = Open
1000 800 600 400 I-BIAS (pA) VOS (V) 200 0 -200 -400 -600 -800 -1000 -1 0 1 V+ = 5V RL = OPEN RF = 100k, RG = 100 AV = +1000 2 3 VCM (V) 4 5 6 100 80 60 40 20 0 -20 -40 -60 -80 -100 -1 0 1 2 3 VCM (V) 4 5 6 V+ = 5V RL = OPEN RF= 100k, RG = 100 AV = +1000
(Continued)
FIGURE 13. INPUT OFFSET VOLTAGE vs COMMON MODE INPUT VOLTAGE
FIGURE 14. INPUT BIAS CURRENT vs COMMON-MODE INPUT VOLTAGE
350 330 310 CURRENT (A) 290 270 250 230 210 190 170 -40 -20 0 20 40 60 80 100 120 MIN MEDIAN CURRENT (A) N = 1000 MAX
4.8 n = 12 4.6 4.4 4.2 4 3.8 3.6 3.4 3.2 -40 -20 0 20 40 60 80 TEMPERATURE (C) 100 120 MIN MEDIAN MAX
TEMPERATURE (C)
FIGURE 15. ISL28488 SUPPLY CURRENT vs TEMPERATURE V+, V- = 2.5V ENABLED, RL = INF
FIGURE 16. ISL28288 SUPPLY CURRENT vs TEMPERATURE V+, V- = 2.5V DISABLED, RL = INF
2 1.5 1
N = 1000
MAX
2 1.5 1
N = 1000
MAX
VOS (mV)
VOS (mV)
0.5 0 -0.5 -1 MIN -1.5 -2 -2.5 -40 -20 0 20 40 60 80 100 120 MEDIAN
0.5 0 -0.5 -1 -1.5 -2 -2.5 -40 -20 0 20 40 60 80 100 120 MIN MEDIAN
TEMPERATURE (C)
TEMPERATURE (C)
FIGURE 17. VOS vs TEMPERATURE, VIN = 0V, V+, V- = 2.5V
FIGURE 18. VOS vs TEMPERATURE VIN = 0V, V+, V- = 1.2V
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FN6339.1 June 28, 2007
ISL28288, ISL28488 Typical Performance Curves V+ = 5V, V- = 0V, VCM = 2.5V, RL = Open
500 n = 1000 0 -500 IBIAS- (pA) MAX -1000 -1500 MEDIAN -2000 MIN -2500 -40 -20 0 20 40 60 80 100 120 0 -200 IBIAS+ (pA) -400 -600 -800 -1000 -1200 -1400 -40 -20 0 20 40 60 MEDIAN MAX 200 n = 1000
(Continued)
MIN 80 100 120
TEMPERATURE (C)
TEMPERATURE (C)
FIGURE 19. IBIAS+ vs TEMPERATURE V+, V- = 2.5V
FIGURE 20. IBIAS- vs TEMPERATURE V+, V- = 2.5V
500 n = 1000 0 -500 MAX -1000 -1500 -2000 MIN -2500 -40 -20 0 20 40 60 80 100 120
200 n = 1000 0 -200 IBIAS- (pA) -400 -600 -800 -1000 MIN -1200 -40 -20 0 20 40 60 80 100 120 MEDIAN MAX
IBIAS+ (pA)
MEDIAN
TEMPERATURE (C)
TEMPERATURE (C)
FIGURE 21. IBIAS+ vs TEMPERATURE V+, V- = 1.2V
FIGURE 22. IBIAS- vs TEMPERATURE V+, V- = -1.2V
200 n = 1000 0 -200 IOS (pA) -400 -600 -800 -1000 -1200 -1400 -40 -20 0 20 40 60 MEDIAN AVOL (V/mV) MAX
650 600 550 500 450 400 350 300 250 MIN 80 100 120 200 150 -40 -20 0 MIN 20 40 60 80 100 120 MEDIAN n = 1000 MAX
TEMPERATURE (C)
TEMPERATURE (C)
FIGURE 23. IOS vs TEMPERATURE V+, V- = 2.5V
FIGURE 24. AVOL vs TEMPERATURE V+, V- = 2.5V, RL=100k
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FN6339.1 June 28, 2007
ISL28288, ISL28488 Typical Performance Curves V+ = 5V, V- = 0V, VCM = 2.5V, RL = Open
90 n = 1000 80 MAX AVOL (V/mV) MEDIAN 60 50 40 30 MIN CMRR (dB) 70 115 105 95 MIN 85 75 125 135
(Continued)
n = 1000 MAX
MEDIAN
-40
-20
0
20
40
60
80
100
120
-40
-20
0
20
40
60
80
100
120
TEMPERATURE (C)
TEMPERATURE (C)
FIGURE 25. AVOL vs TEMPERATURE, V+, V- = 2.5V, RL=1k
FIGURE 26. CMRR vs TEMPERATURE VCM = +2.5V TO -2.5V, V+, V- = 2.5V
140 n = 1000 130 120 VOUT (V) MAX
4.91 n = 1000 4.90 4.89 MAX
PSRR (dB)
4.88 MEDIAN 4.87 4.86
110 100 90 80
MEDIAN
MIN 4.85 4.84 -40
MIN
-40
-20
0
20
40
60
80
100
120
-20
0
20
40
60
80
100
120
TEMPERATURE (C)
TEMPERATURE (C)
FIGURE 27. PSRR vs TEMPERATURE, V+, V- = 1.2V TO 2.75V
FIGURE 28. VOUT HIGH vs TEMPERATURE, V+, V- = 2.5V, RL= 1k
4.9984 4.9982 4.9980 4.9978 VOUT (V) VOUT (mV) 4.9976 4.9974 4.9972 4.9970 4.9968 4.9966 4.9964 -40 -20 0 20 40 60 80 100 120 MEDIAN MIN n = 12 MAX
170 n = 1000 160 MAX 150 140 130 120 MIN 110 100 -40 -20 0 20 40 60 80 100 120 MEDIAN
TEMPERATURE (C)
TEMPERATURE (C)
FIGURE 29. VOUT HIGH vs TEMPERATURE, V+, V- = 2.5V, RL= 100k
FIGURE 30. VOUT LOW vs TEMPERATURE, V+, V- = 2.5V, RL= 1k
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FN6339.1 June 28, 2007
ISL28288, ISL28488 Typical Performance Curves V+ = 5V, V- = 0V, VCM = 2.5V, RL = Open
n = 12 +OUTPUT SHORT CIRCUIT CURRENT (mA) 4.3 4.2 4.1 VOUT (mV) 4.0 3.9 3.8 3.7 MIN 3.6 3.5 3.4 -40 -20 0 20 40 60 80 100 120 MEDIAN MAX 39 n = 1000 37 35 33 31 29 MIN 27 25 -40 -20 0 20 40 60 80 100 120
(Continued)
MAX
MEDIAN
TEMPERATURE (C)
TEMPERATURE (C)
FIGURE 31. VOUT LOW vs TEMPERATURE, V+, V- = 2.5V, RL= 100k
FIGURE 32. +OUTPUT SHORT CIRCUIT CURRENT vs TEMPERATURE VIN = +2.5V, RL = 10, V+, V- = 2.5V
-OUTPUT SHORT CIRCUIT CURRENT (mA)
-21 n = 1000 -23 MAX -25 -27 MEDIAN -29 MIN -31 -33
-40
-20
0
20
40
60
80
100
120
TEMPERATURE (C)
FIGURE 33. -OUTPUT SHORT CIRCUIT CURRENT vs TEMPERATURE VIN = -2.5V, RL = 10, V+, V- = 2.5V
Pin Descriptions
ISL28288 ISL28488 (10 LD MSOP) (16 LD QSOP) 1 2 3 4 5 6 7 8 9 10 5 6 7 4 1 2 13 3 PIN NAME IN+_A EN_A VEN_B IN+_B IN-_B OUT_B V+ OUT_A IN-_A EQUIVALENT CIRCUIT Circuit 1 Circuit 2 Circuit 4 Circuit 2 Circuit 1 Circuit 1 Circuit 3 Circuit 4 Circuit 3 Circuit 1 Amplifier A non-inverting input Amplifier A enable pin internal pull-down; Logic "1" selects the disabled state; Logic "0" selects the enabled state. Negative power supply Amplifier B enable pin with internal pull-down; Logic "1" selects the disabled state; Logic "0" selects the enabled state. Amplifier B non-inverting input Amplifier B inverting input Amplifier B output Positive power supply Amplifier A output Amplifier A inverting input DESCRIPTION
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FN6339.1 June 28, 2007
ISL28288, ISL28488 Pin Descriptions (Continued)
ISL28288 ISL28488 (10 LD MSOP) (16 LD QSOP) 10 11 12 14 15 16 8, 9
V+ INLOGIC PIN VCIRCUIT 2 CIRCUIT 3
PIN NAME OUT_C IN-_C IN+_C IN+_D IN-_D OUT_D NC
EQUIVALENT CIRCUIT Circuit 3 Circuit 1 Circuit 1 Circuit 1 Circuit 1 Circuit 3 Amplifier C output Amplifier C inverting input Amplifier C non-inverting input Amplifier D non-inverting input Amplifier D inverting input Amplifier D output No internal connection
V+
DESCRIPTION
V+ OUT V-
V+
CAPACITIVELY COUPLED ESD CLAMP
IN+ V-
VCIRCUIT 4
CIRCUIT 1
Applications Information
Introduction
The ISL28288 and ISL28488 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 120A of supply current. This combination of low power and precision performance makes these devices suitable for solar and battery power applications.
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.
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 ISL28288 with a 100k load will swing to within 4mV of the positive supply rail and within 3mV of the negative supply rail.
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 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).
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 4A. 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 loading effects of the feedback resistors of the disabled amplifier must be considered when multiple amplifier outputs are connected together. 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.
Using Only One Channel
The ISL28288 is a dual op amp. 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
Input Protection
All input terminals have internal ESD protection diodes to both positive and negative supply rails, limiting the input voltage to
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FN6339.1 June 28, 2007
ISL28288, ISL28488
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 34).
ISL28288 +
.
R4 100k R3 R2 K TYPE THERMOCOUPLE 10k 10k V+ + ISL28X88 V-
410V/C + 5V
R1
FIGURE 34. PREVENTING OSCILLATIONS IN UNUSED CHANNELS
100k
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 35 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, components can be mounted to the PC board using Teflon standoff insulators.
HIGH IMPEDANCE INPUT IN V+
FIGURE 36. THERMOCOUPLE AMPLIFIER
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
It is possible to exceed the +150C 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 in Equation 1:
T JMAX = T MAX + ( 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 is calculated in Equation 2:
V OUTMAX PD MAX = 2*V S x I SMAX + ( V S - V OUTMAX ) x --------------------------R
L
(EQ. 2) FIGURE 35. GUARD RING EXAMPLE FOR UNITY GAIN AMPLIFIER
where: * TMAX = Maximum ambient temperature * JA = Thermal resistance of the package * PDMAX = Maximum power dissipation of 1 amplifier * VS = Supply voltage (Magnitude of V+ and V-) * IMAX = Maximum supply current of 1 amplifier * VOUTMAX = Maximum output voltage swing of the application * RL = Load resistance
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 36) 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.
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FN6339.1 June 28, 2007
ISL28288, ISL28488 Quarter Size Outline Plastic Packages Family (QSOP)
A D N (N/2)+1
MDP0040
QUARTER SIZE OUTLINE PLASTIC PACKAGES FAMILY INCHES SYMBOL QSOP16 QSOP24 QSOP28 TOLERANCE NOTES
PIN #1 I.D. MARK
A A1 A2 b
0.068 0.006 0.056 0.010 0.008 0.193 0.236 0.154 0.025 0.025 0.041 16
0.068 0.006 0.056 0.010 0.008 0.341 0.236 0.154 0.025 0.025 0.041 24
0.068 0.006 0.056 0.010 0.008 0.390 0.236 0.154 0.025 0.025 0.041 28
Max. 0.002 0.004 0.002 0.001 0.004 0.008 0.004 Basic 0.009 Basic Reference
1, 3 2, 3 Rev. F 2/07
E
E1
1 B 0.010 CAB
(N/2)
c D E
e C SEATING PLANE 0.004 C 0.007 CAB b
H
E1 e L L1 N
L1 A c SEE DETAIL "X"
NOTES: 1. Plastic or metal protrusions of 0.006" maximum per side are not included. 2. Plastic interlead protrusions of 0.010" maximum per side are not included. 3. Dimensions "D" and "E1" are measured at Datum Plane "H". 4. Dimensioning and tolerancing per ASME Y14.5M-1994.
0.010 A2 GAUGE PLANE L 44 DETAIL X
A1
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FN6339.1 June 28, 2007
ISL28288, ISL28488 Mini SO Package Family (MSOP)
0.25 M C A B D N A (N/2)+1
MDP0043
MINI SO PACKAGE FAMILY MILLIMETERS SYMBOL A A1 MSOP8 1.10 0.10 0.86 0.33 0.18 3.00 4.90 3.00 0.65 0.55 0.95 8 MSOP10 1.10 0.10 0.86 0.23 0.18 3.00 4.90 3.00 0.50 0.55 0.95 10 TOLERANCE Max. 0.05 0.09 +0.07/-0.08 0.05 0.10 0.15 0.10 Basic 0.15 Basic Reference NOTES 1, 3 2, 3 Rev. D 2/07 NOTES: 1. Plastic or metal protrusions of 0.15mm maximum per side are not included.
E
E1
PIN #1 I.D.
A2 b c
B
1 (N/2)
D E E1
e C SEATING PLANE 0.10 C N LEADS b
H
e L L1 N
0.08 M C A B
L1 A c SEE DETAIL "X"
2. Plastic interlead protrusions of 0.25mm maximum per side are not included. 3. Dimensions "D" and "E1" are measured at Datum Plane "H". 4. Dimensioning and tolerancing per ASME Y14.5M-1994.
A2 GAUGE PLANE L DETAIL X
0.25
A1
3 3
All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. Intersil Corporation's quality certifications can be viewed at www.intersil.com/design/quality
Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries.
For information regarding Intersil Corporation and its products, see www.intersil.com 13
FN6339.1 June 28, 2007

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