Datasheet ISL28488 Datasheet (intersil)

Page 1

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ISL28288, ISL28488

Data Sheet June 28, 2007

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 4µA in the disabled state.

Pinouts

ISL28288

(10 LD MSOP)

TOP VIEW

IN+_A

V-

IN+_B IN-_B

5 6

ISL28488

(16 LD QSOP)

TOP VIEW

OUT_A

IN-_A

IN+_A

V+

IN+_B IN+_C

IN-_B

IN-_A

OUT_A

V+

OUT_B

OUT_D

IN-_D

IN+_D

V-

IN-_C

FN6339.1

Features

• Low power 120µA 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

• Handheld consumer products

• Medical devices

• Thermocouple amplifiers

• Photodiode pre-amps

• pH probe amplifiers

Ordering Information

PART NUMBER

(Note)

ISL28288FUZ 8288Z 10 Ld MSOP MDP0043 ISL28288FUZ-T7 8288Z 10 Ld MSOP MDP0043 ISL28488FAZ 28488 FAZ 16 Ld QSOP MDP0040 ISL28488FAZ-T7 28488 FAZ 16 Ld QSOP MDP0040 *“-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.

PART

MARKING

PACKAGE

(Pb-Free)

PKG. DWG.

OUT_B

NC NC

8 9

OUT_C

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.

All other trademarks mentioned are the property of their respective owners.

Page 2

ISL28288, ISL28488

Absolute Maximum Ratings (T

Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5V

Supply Turn On Voltage Slew Rate . . . . . . . . . . . . . . . . . . . . . 1V/μs

Differential Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA

Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5V

Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . V-

ESD Tolerance

Human Body Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3kV

Machine Model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .300V

= +25°C) Thermal Information

Thermal Resistance θ

10 Ld MSOP Package . . . . . . . . . . . . . . . . . . . . . . . 115

16 Ld QSOP Package . . . . . . . . . . . . . . . . . . . . . . . 112

- 0.5V to V+ + 0.5V

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

Pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . . .see link below

(°C/W)

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: T

Operating Junction

Electrical Specifications V

= 5V, V- = 0V, VCM = 2.5V, RL = Open, TA = +25°C unless otherwise specified.

= TC = T

Boldface limits apply over the operating temperature range, -40°C to +125°C. Temperature data established by characterization

PARAMETER DESCRIPTION CONDITIONS

MIN

(Note 1) TYP

MAX

(Note 1) UNIT

DC SPECIFICATIONS

ΔV

------------------

ΔTi me

ΔV

--------------- -

ΔT

Input Offset Voltage -1.5

-2

±0.05 1.5

Long Term Input Offset Voltage Stability ISL28288 1.2 µV/Mo

Input Offset Voltage vs Temperature 0.9 µV/°C

Input Offset Current

-40°C to +85°C

Input Bias Current

-40°C to +85°C

-30

-80

-30

-80

±530

±10 30

CMIR Common-Mode Voltage Range Guaranteed by CMRR 05V CMRR Common-Mode Rejection Ratio V

PSRR Power Supply Rejection Ratio V

= 0V to 5V 80

= 2.4V to 5V 85

100 dB

105 dB

VOL

OUT

Large Signal Voltage Gain VO = 0.5V to 4.5V, RL = 100kΩ 200

190

= 0.5V to 4.5V, RL = 1kΩ 60 V/mV

Maximum Output Voltage Swing Output low, RL = 100kΩ 3630mV

300 V/mV

S,ON

Output low, R

Output high, R

= 1kΩ 130 175

= 100kΩ 4.990

4.996 V

225

4.97

Output high, R

= 1kΩ 4.800

4.750

4.880 V

Quiescent Supply Current, Enabled ISL28288, All channels enabled. 120 156

175

ISL28488, All channels enabled. 240 315

350

µA

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June 28, 2007

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ISL28288, ISL28488

Electrical Specifications V

= 5V, V- = 0V, VCM = 2.5V, RL = Open, TA = +25°C unless otherwise specified.

Boldface limits apply over the operating temperature range, -40°C to +125°C. Temperature data established by characterization (Continued)

MIN

PARAMETER DESCRIPTION CONDITIONS

S,OFF

+ Short Circuit Sourcing Capability RL = 10Ω 29

- Short Circuit Sinking Capability RL = 10Ω 24

Quiescent Supply Current, Disabled (ISL28288)

All channels disabled. 4 7

(Note 1) TYP

SUPPLY

ENH

ENL

ENH

ENL

Supply Operating Range V+ to V- 2.4 5.0 V EN Pin High Level (ISL28288) 2 V EN Pin Low Level (ISL28288) 0.8 V EN Pin Input High Current (ISL28288) VEN = V

EN Pin Input Low Current (ISL28288) VEN = V

AC SPECIFICATIONS

GBW Gain Bandwidth Product A

Input Noise Voltage Peak-to-Peak f = 0.1Hz to 10Hz 5.4 µV

= 100, RF = 100kΩ, RG = 1kΩ,

= 10kΩ to V

Input Noise Voltage Density fO = 1kHz 48 nV/√Hz

CMRR @ 60Hz Input Common Mode Rejection Ratio V PSRR+ @

120Hz PSRR- @

120Hz

Input Noise Current Density fO = 1kHz 0.1 pA/√Hz

= 1V

, RL = 10kΩ to V

P-P

= 1V

, RL = 10kΩ to V

P-P

= 1V

, RL = 10kΩ to V

P-P

Power Supply Rejection Ratio (V

, V- = ±1.2V and ±2.5V,

SOURCE

, V- = ±1.2V and ±2.5V

SOURCE

TRANSIENT RESPONSE

SR Slew Rate

Enable to Output Turn-on Delay Time, 10% EN

Enable to Output Turn-off Delay Time, 10% EN

to 10% Vout, (ISL28288)

VEN

= 5V to 0V, AV = -1,

RG = RF = RL = 1k

= 0V to 5V, AV = -1,

VEN

RG = RF = RL = 1k

to V

±0.12 ±0.09

±0.14 ±0.16

NOTE:

1. Parts are 100% tested at +25°C. Over temperature limits established by characterization and are not production tested.

MAX

(Note 1) UNIT

µA

31 mA

26 mA

0.8 1

µA

1.5

0 +0.1 µA

300 kHz

P-P

-70 dB

-80 dB

-60 dB

V/µs

±0.21

2µs

0.1 µs

FN6339.1

June 28, 2007

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ISL28288, ISL28488

Typical Performance Curves V

-1

-2

-3

-4

GAIN (dB)

-5

V AV = 1

-6

C R

-7 8

V+, V-= ±2.5V

RL = 1k

V+, V- = ±2.5V

RL = 10k

= 50mV

OUT

= 3pF

= 0, RG = INF

P-P

10k 100k 1M

FREQUENCY (Hz)

= 5V, V- = 0V, VCM = 2.5V, RL = Open

V+, V- = ±1.2V

RL = 1k

V+, V- = ±1.2V

RL = 10k

FIGURE 1. FREQUENCY RESPONSE vs SUPPLY VOLTAGE

120

GAIN (dB)

-40

-80 11k100k10M

FREQUENCY (Hz)

FIGURE 3. A

vs FREQUENCY @ 100kΩ LOAD

VOL

10k 1M100

-40

-80

-120

45 40 35 30 25 20

AV = 100

GAIN (dB)

= 10kΩ

= 3pF

= 100kΩ

= 1kΩ

5 0

100 10k 100k 1M

V+, V- = ±1.0V

FREQUENCY (Hz)

V+, V- = ±2.5V

V+, V- = ±1.2V

FIGURE 2. FREQUENCY RESPONSE vs SUPPLY VOLTAGE

100

PHASE (°)

GAIN (dB)

-20 10 10k 1M

FIGURE 4. A

100

FREQUENCY (Hz)

VOL

PHASE

GAIN

100k1k

vs FREQUENCY @ 1kΩ LOAD

200 150 100 50 0

-50

-100

-150

PHASE (°)

= 5VDC

-10

RL = 10kΩ

-20

-30

-40

-50

PSRR (dB)

-60

-70

-80

-90

-100 10 100 1k 10k 100k

SOURCE

= +1

= 1V

P-P

PSRR -

FREQUENCY (Hz)

PSRR +

, V- = ±2.5VDC

-10 RL = 10kΩ

-20

-30

-40

-50

-60

CMRR (dB)

-70

-80

-90

-100 10 100 1k 10k 100k

SOURCE

= 1V

P-P

FREQUENCY (Hz)

FIGURE 5. PSRR vs FREQUENCY FIGURE 6. CMRR vs FREQUENCY

FN6339.1

June 28, 2007

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ISL28288, ISL28488

Typical Performance Curves V

10.00

1.00

0.10

CURRENT NOISE (pA/√Hz)

0.01 1 10 100 1k 10k

FREQUENCY (Hz)

FIGURE 7. CURRENT NOISE vs FREQUENCY FIGURE 8. VOLTAGE NOISE vs FREQUENCY

= 5V, V- = 0V, VCM = 2.5V, RL = Open (Continued)

100

VOLTAGE NOISE (nV/√Hz)

100k

1 10 100 10k 100k

2.56 V

2.54

2.52

2.50

FREQUENCY (Hz)

OUT

2.48

= 5VDC

= 0.1V

OUT

RL = 1kΩ A

= +1

TIME (µs)

P-P

VOLTAGE NOISE (1µV/DIV)

5.4µV

P-P

TIME (1s/DIV)

VOLTS (V)

2.46

2.44

2.42

0 2 4 6 8 101214161820

FIGURE 9. 0.1Hz TO 10Hz INPUT VOLTAGE NOISE FIGURE 10. SMALL SIGNAL TRANSIENT RESPONSE

VOLTS (V)

5.0

4.0

3.0

2.0

1.0

= 5VDC

= 2V

OUT

RL = 1kΩ A

= -2

P-P

OUT

EN INPUT

1V/DIV0.1V/DIV

OUT

AV = -1

= 200mV

V+ = 5V

= 0V

P-P

0 50 100 150 200 250

TIME (µs)

FIGURE 11. LARGE SIGNAL TRANSIENT RESPONSE

10µs/DIV

FIGURE 12. ENABLE TO OUTPUT DELAY TIME

FN6339.1

June 28, 2007

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ISL28288, ISL28488

Typical Performance Curves V

1000

800 600 400 200

(µV)

-200

-400

-600

-800

-1000

-10123456

V+ = 5V

= OPEN

= 100k, RG = 100

= +1000

(V)

= 5V, V- = 0V, VCM = 2.5V, RL = Open (Continued)

FIGURE 13. INPUT OFFSET VOLTAGE vs COMMON MODE

INPUT VOLTAGE

350

N = 1000

330 310 290 270 250

CURRENT (µA)

230 210 190 170

-40 -20 0 20 40 60 80 100 120

MAX

MEDIAN

MIN

TEMPERATURE (°C)

FIGURE 15. ISL28488 SUPPL Y CURRENT vs TEMPERA TURE

, V- = ±2.5V ENABLED, RL = INF

100

80 60 40 20

(pA)

-20

-BIAS

-40

-60

-80

-100

-10123456

V+ = 5V

= OPEN

= 100k, RG = 100

= +1000

(V)

FIGURE 14. INPUT BIAS CURRENT vs COMMON-MODE

INPUT VOLTAGE

4.8

n = 12

4.6

4.4

4.2

3.8

CURRENT (µA)

3.6

3.4

3.2

-40-200 20406080100120

MEDIAN

MAX

MIN

TEMPERATURE (°C)

FIGURE 16. ISL28288 SUPPL Y CURRENT vs TEMPERA TURE

, V- = ±2.5V DISABLED, RL = INF

N = 1000

1.5 1

0.5

(mV)

-0.5

-1

-1.5

-2

-2.5

-40-200 20406080100120

FIGURE 17. V

vs TEMPERATURE, V

MAX

MEDIAN

MIN

TEMPERATURE (°C)

= 0V, V+, V- = ±2.5V

N = 1000

1.5 1

0.5

(mV)

-0.5

-1

-1.5

-2

-2.5

-40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C)

FIGURE 18. V

vs TEMPERATURE V

MAX

MEDIAN

MIN

= 0V, V+, V- = ±1.2V

FN6339.1

June 28, 2007

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ISL28288, ISL28488

Typical Performance Curves V

500

n = 1000

-500

(pA)

-1000

BIAS+

-1500

-2000

-2500

-40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C)

FIGURE 19. I

500

n = 1000

-500

(pA)

-1000

BIAS+

-1500

-2000

-2500

-40 -20 0 20 40 60 80 100 120

FIGURE 21. I

vs TEMPERATURE V+, V- = ±2.5V FIGURE 20. I

BIAS+

TEMPERATURE (°C)

+ vs TEMPERATURE V+, V- = ±1.2V

BIAS

= 5V, V- = 0V, VCM = 2.5V, RL = Open (Continued)

200

n = 1000

-200

MAX

MEDIAN

MIN

MAX

MEDIAN

MIN

-400

(pA)

-600

BIAS-

-800

-1000

-1200

-1400

-40 -20 0 20 40 60 80 100 120

200

n = 1000

-200

-400

(pA)

-600

BIAS-

-800

-1000

-1200

-40 -20 0 20 40 60 80 100 120

FIGURE 22. I

MEDIAN

TEMPERATURE (°C)

- vs TEMPERATURE V+, V- = ±2.5V

BIAS

MAX

MEDIAN

TEMPERATURE (°C)

- vs TEMPERATURE V+, V- = ±-1.2V

BIAS

MAX

MIN

200

n = 1000

-200

-400

(pA)

-600

-800

-1000

-1200

-1400

-40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C)

FIGURE 23. I

vs TEMPERATURE V+, V- = ±2.5V

MEDIAN

MAX

MIN

650 600

n = 1000

550 500 450

(V/mV)

400

VOL

350

300 250 200 150

-40 -20 0 20 40 60 80 100 120

FIGURE 24. A

vs TEMPERATURE V+, V- = ±2.5V , RL=100k

VOL

MAX

MEDIAN

MIN

TEMPERATURE (°C)

FN6339.1

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Page 8

ISL28288, ISL28488

Typical Performance Curves V

n = 1000

(V/mV)

VOL

-40 -20 0 20 40 60 80 100 120

FIGURE 25. A

140

130

120

110

PSRR (dB)

100

MEDIAN

vs TEMPERATURE, V+, V- = ±2.5V, RL=1k

VOL

n = 1000

MAX

MIN

TEMPERATURE (°C)

MAX

MEDIAN

MIN

= 5V, V- = 0V, VCM = 2.5V, RL = Open (Continued)

135

n = 1000

125

115

105

CMRR (dB)

-40 -20 0 20 40 60 80 100 120

FIGURE 26. CMRR vs TEMPERATURE V

, V- = ±2.5V

4.91 n = 1000

VOUT (V)

4.90

4.89

4.88

4.87

4.86

4.85

MAX

MEDIAN

MIN

TEMPERATURE (°C)

MAX

MEDIAN

MIN

= +2.5V TO -2.5V ,

-40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C)

FIGURE 27. PSRR vs TEMPERATURE, V

4.9984

4.9982

4.9980

4.9978

4.9976

4.9974

4.9972

VOUT (V)

4.9970

4.9968

4.9966

4.9964

FIGURE 29. V

n = 12

MAX

MEDIAN

MIN

-40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C)

HIGH vs TEMPERATURE,

OUT

= ±2.5V, RL= 100k

+, V-

= ±1.2V TO ±2.75V

+, V-

4.84

-40 -20 0 20 40 60 80 100 120 TEMPERATURE (°C)

FIGURE 28. V

170

160

150

140

130

VOUT (mV)

120

110

100

-40 -20 0 20 40 60 80 100 120

FIGURE 30. V

HIGH vs TEMPERATURE,

OUT

= ±2.5V, RL= 1k

+, V-

n = 1000

MIN

TEMPERATURE (°C)

LOW vs TEMPERATURE,

OUT

= ±2.5V, RL= 1k

+, V-

MAX

MEDIAN

FN6339.1

June 28, 2007

Page 9

ISL28288, ISL28488

Typical Performance Curves V

4.3 n = 12

4.2

4.1

4.0

3.9

(mV)

3.8

OUT

3.7

3.6

3.5

3.4

-40 -20 0 20 40 60 80 100 120

FIGURE 31. V

MEDIAN

LOW vs TEMPERATURE,

OUT

= ±2.5V, RL= 100k

+, V-

MAX

MIN

TEMPERATURE (°C)

= 5V, V- = 0V, VCM = 2.5V, RL = Open (Continued)

n = 1000

(mA)

+OUTPUT SHORT CIRCUIT CURRENT

-40 -20 0 20 40 60 80 100 120

FIGURE 32. +OUTPUT SHORT CIRCUIT CURRENT vs

TEMPERATURE V V

+, V-

-21 n = 1000

-23

-25

MAX

TEMPERATURE (°C)

= ±2.5V

MAX

MEDIAN

MIN

= +2.5V, RL = 10,

-27

(mA)

-29

-31

-33

-OUTPUT SHORT CIRCUIT CURRENT

-40-200 20406080100120

MIN

TEMPERATURE (°C)

FIGURE 33. -OUTPUT SHORT CIRCUIT CURRENT vs TEMPERATURE V

Pin Descriptions

ISL28288

(10 LD MSOP)

1 3 IN+_A Circuit 1 Amplifier A non-inverting input 2EN

3 13 V- Circuit 4 Negative power supply 4EN

5 5 IN+_B Circuit 1 Amplifier B non-inverting input 6 6 IN-_B Circuit 1 Amplifier B inverting input 7 7 OUT_B Circuit 3 Amplifier B output 8 4 V+ Circuit 4 Positive power supply 9 1 OUT_A Circuit 3 Amplifier A output

10 2 IN-_A Circuit 1 Amplifier A inverting input

ISL28488

(16 LD Q SOP) PIN NAME

_A Circuit 2 Amplifier A enable pin internal pull-down; Logic “1” selects the disabled state;

_B Circuit 2 Amplifier B enable pin with internal pull-down; Logic “1” selects the disabled state;

EQUIVALENT

CIRCUIT DESCRIPTION

Logic “0” selects the enabled state.

MEDIAN

= -2.5V, RL = 10, V

+, V-

= ±2.5V

FN6339.1

June 28, 2007

Page 10

Pin Descriptions (Continued)

ISL28288, ISL28488

ISL28288

(10 LD MSOP)

IN-

ISL28488

(16 LD Q SOP) PIN NAME

10 OUT_C Circuit 3 Amplifier C output 11 IN-_C Circuit 1 Amplifier C inverting input 12 IN+_C Circuit 1 Amplifier C non-inverting input 14 IN+_D Circuit 1 Amplifier D non-inverting input 15 IN-_D Circuit 1 Amplifier D inverting input 16 OUT_D Circuit 3 Amplifier D output

8, 9 NC - No internal connection

V+

IN+

V-

CIRCUIT 1

EQUIVALENT

CIRCUIT DESCRIPTION

LOGIC

CIRCUIT 2

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 120μA 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 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 volt age to

V+

V-

V+

OUT

V-

CIRCUIT 3

V+

V-

CIRCUIT 4

CAPACITIVELY

COUPLED ESD CLAMP

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 100kΩ load will swing to within 4mV of the positive supply rail and within 3mV of the negative supply rail.

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 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

FN6339.1

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ISL28288, ISL28488

noise injection into the channel being used. The proper wa y to prevent this oscillation is to short the output to the negative input and ground the positive input (as shown in Figure 34).

ISL28288 +

FIGURE 34. 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 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

FIGURE 35. GUARD RING EXAMPLE FOR UNITY GAIN

AMPLIFIER

V+

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 th e thermocouple to be biased at ground and the amplifier to run from a single 5V supply.

K TYPE

THERMOCOUPLE

FIGURE 36. THERMOCOUPLE AMPLIFIER

10kΩR

100kΩ

ISL28X88

V+

V-

100kΩ

410µV/°C

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 +150°C maximum junction temperatures under certain load and power-supply conditions. It is therefore important to calculate the maximum junction temperature (T 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:

JMAXTMAXθJA

xPD

()+=

MAXTOTAL

where:

•P

DMAXTOTAL

is the sum of the maximum power

dissipation of each amplifier in the package (PD

•PD

for each amplifier is calculated in Equation 2:

MAX

2*VSI

( - V

SMAXVS

where:

•T

• θ

•PD

•V

•I

•V

= Maximum ambient temperature

MAX

= Thermal resistance of the package

= Maximum power dissipation of 1 amplifier

MAX

= Supply voltage (Magnitude of V+ and V-)

= Maximum supply current of 1 amplifier

MAX

OUTMAX

= Maximum output voltage swing of the

application

•R

= Load resistance

) for all applications

JMAX

----------------------------

)

OUTMAX

×+×=

MAX

OUTMAX

(EQ. 1)

)

(EQ. 2)

FN6339.1

June 28, 2007

Page 12

ISL28288, ISL28488

Quarter Size Outline Plastic Packages Family (QSOP)

E E1

0.010 C A B

SEATING PLANE

0.004 C

PIN #1 I.D. MARK

SEE DETAI L "X"

0.007 C A B

(N/2)+1

(N/2)

MDP0040

QUARTER SIZE OUTLINE PLASTIC PACKAGES FAMILY

INCHES

SYMBOL

A 0.068 0.068 0.068 Max. A1 0.006 0.006 0.006 ±0.002 A2 0.056 0.056 0.056 ±0.004 -

b 0.010 0.010 0.010 ±0.002 -

c 0.008 0.008 0.008 ±0.001 -

D 0.193 0.341 0.39 0 ±0.004 1, 3

E 0.236 0.236 0.236 ±0.008 -

E1 0.154 0.154 0.154 ±0.004 2, 3

e 0.025 0.025 0.025 Basic -

L 0.025 0.025 0.025 ±0.009 -

L1 0.041 0.041 0.041 Basic -

N 16 24 28 Reference -

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.

TOLERANCE NOTESQSOP16 QSOP24 QSOP28

Rev. F 2/07

DETAIL X

GAUGE PLANE

0.010

4°±4°

FN6339.1

June 28, 2007

Page 13

Mini SO Package Family (MSOP)

SEATING PLANE

0.10 C

N LEADS

0.25 C A B

E1E

SEE DETAIL "X"

(N/2)+1

PIN #1 I.D.

(N/2)

0.08 C A B

ISL28288, ISL28488

MDP0043

MINI SO PACKAGE FAMILY

SYMBOL

A1.101.10 Max. A1 0.10 0.10 ±0.05 A2 0.86 0.86 ±0.09 -

b 0.33 0.23 +0.07/-0.08 -

c0.180.18 ±0.05 D 3.00 3.00 ±0.10 1, 3 E4.904.90 ±0.15 -

E1 3.00 3.00 ±0.10 2, 3

e0.650.50 Basic -

L0.550.55 ±0.15 -

L1 0.95 0.95 Basic -

N 8 10 Reference -

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.

3. Dimensions “D” and “E1” are measured at Datum Plane “H”.

4. Dimensioning and tolerancing per ASME Y14.5M-1994.

MILLIMETERS

TOLERANCE NOTESMSOP8 MSOP10

Rev. D 2/07

GAUGE

DETAIL X

PLANE

3° ±3°

0.25

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 implicat ion or oth erwise u nde r any p a tent or p at ent r ights of Intersil or its subsidiari es.

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FN6339.1

June 28, 2007