EL8172FSZ_技术文档

EL8171, EL8172

®

Data Sheet

August 3, 2007

FN6293.3

Micropower, Single Supply, Rail-to-Rail

Input-Output Instrumentation Amplifiers

Features

• 95µA maximum supply current

The EL8171 and EL8172 are micropower instrumentation

amplifiers optimized for single supply operation over the

+2.4V to +5.5V range. Inputs and outputs can operate rail-to-

rail. As with all instrumentation amplifiers, a pair of inputs

provide very high common-mode rejection and are

completely independent from a pair of feedback terminals.

The feedback terminals allow zero input to be translated to

any output offset, including ground. A feedback divider

controls the overall gain of the amplifier.

• Maximum input offset voltage

- 300µV (EL8172)

- 1500µV (EL8171)

• 50pA maximum input bias current

• 450kHz -3dB bandwidth (G = 10)

• 170kHz -3dB bandwidth (G = 100)

• Single supply operation

- Input voltage range is rail-to-rail

- Output swings rail-to-rail

- Ground Sensing

The EL8172 is compensated for a gain of 100 or more, and

the EL8171 is compensated for a gain of 10 or more. The

EL8171 and EL8172 have PMOS input devices that provide

sub-nA input bias currents.

• Pb-free plus anneal available (RoHS compliant)

The amplifiers can be operated from one lithium cell or two

Ni-Cd batteries. The EL8171 and EL8172 input range goes

from below ground to slightly above positive rail. The output

stage swings completely to ground (ground sensing) or

positive supply - no pull-up or pull-down resistors are

needed.

Applications

• Battery- or solar-powered systems

• Strain gauges

• Current monitors

• Thermocouple amplifiers

Pinout

EL8171, EL8172

(8 LD SOIC)

TOP VIEW

Ordering Information

PART

NUMBER

(Note)

PART

MARKING

PACKAGE

(Pb-free)

PKG.

DWG. #

+

EN

IN-

IN+

V-

1

2

3

4

8

7

6

5

FB+

V+

-

EL8171FSZ*

EL8172FSZ*

8171FSZ

8172FSZ

8 Ld SOIC

MDP0027

-

Σ

+

VOUT

FB-

*Add “-T7” suffix 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.

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.

1

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

EL8171, EL8172

Absolute Maximum Ratings (T = +25°C)

Thermal Information

A

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

+

Thermal Resistance

θ

(°C/W)

110

JA

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

Differential Input Voltage (EL8172) . . . . . . . . . . . . . . . . . . . . . . 0.5V

Differential Input Voltage (EL8171) . . . . . . . . . . . . . . . . . . . . . . 1.0V

8 Ld SOIC Package . . . . . . . . . . . . . . . . . . . . . . . .

Output Short-Circuit Duration . . . . . . . . . . . . . . . . . . . . . . .Indefinite

Ambient Operating Temperature . . . . . . . . . . . . . . .-40°C to +125°C

Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C

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

http://www.intersil.com/pbfree/Pb-FreeReflow.asp

V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.5V to V + 0.5V

EN

+

ESD Rating

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

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 = T = T

A

J

C

Electrical Specifications

V

= +5V, V- = GND, VCM = 1/2V

V

= V-, R = Open, T = +25°C, unless otherwise specified. Boldface

L A

+

EN

limits apply over the operating temperature range, -40°C to +125°C.

MIN

MAX

PARAMETER

DESCRIPTION

CONDITIONS

(Note 1)

TYP

(Note 1) UNIT

DC SPECIFICATIONS

V

Input Offset Voltage

EL8171

EL8172

-1.5

-2

±0.47

±0.07

1.5

2

mV

OS

-0.3

0.3

-0.7

0.7

TCV

Input Offset Voltage Temperature

Coefficient

EL8171

EL8172

1.5

0.14

±4

µV/°C

OS

I

Input Offset Current, ± IN, ± FB

Input Bias Current

-25

-500

25

500

pA

OS

B

-50

-4

±10

50

4

pA

nA

V

Input Voltage Range

Guaranteed by CMRR test

= 0V to +5V

0

75

5

V

IN

CMRR

PSRR

Common Mode Rejection Ratio

Power Supply Rejection Ratio

V

100

90

dB

%

CM

EL8171, V = 2.4V to 5V

75

+

EL8172, V = 2.4V to 5V

75

100

+

E

V

Gain Error

EL8171, R = 100kΩ to 2.5V

-0.7

±0.15

±0.2

0.7

G

L

EL8172, R = 100kΩ to 2.5V

-1

-1.5

+1

1.5

%

L

Maximum Voltage Swing

Output low, 100kΩ to 2.5V

Output low, 1kΩ to 2.5V

Output high, 100kΩ to 2.5V

Output high, 1kΩ to GND

4

10

mV

OUT

0.13

4.996

4.87

65

0.2

0.25

V

4.985

4.980

V

4.860

4.750

V

I

Supply Current, Enabled

Supply Current, Disabled

45

38

95

110

µA

S,EN

S,DIS

EL8171: EN = V

EL8172: EN = V

1.8

1.3

2.6

4

5

+

1.8

4.5

7.0

1.5

25

FN6293.3

August 3, 2007

2

EL8171, EL8172

Electrical Specifications

V

= +5V, V- = GND, VCM = 1/2V

V

= V-, R = Open, T = +25°C, unless otherwise specified. Boldface

EN L A

+

limits apply over the operating temperature range, -40°C to +125°C. (Continued)

MIN

MAX

PARAMETER

DESCRIPTION

CONDITIONS

(Note 1)

TYP

0.5

(Note 1) UNIT

V

EN Pin for Shut-down

EN Pin for Power-on

Supply Operating Range

2

V

ENH

I

µA

ENH

V

0.8

5.5

V

µA

V

ENL

I

0.5

ENL

V

V+ to V- (Note 2)

2.4

SUPPLY

I

Output Source Current into 10Ω to V /2

V

= 5V

23

19

32

8

mA

O+

+

= 2.4V

= 5V

6

4.5

mA

Output Sink Current into 10Ω to V /2

19

15

26

7

O-

+

= 2.4V

5

4

AC SPECIFICATIONS

-3dB BW -3dB Bandwidth

EL8171

EL8172

Gain = 10V/V

Gain = 20

450

210

66

kHz

Gain = 50

Gain = 100

Gain = 200

Gain = 500

Gain = 1000

f = 0.1Hz to 10Hz

33

170

70

25

12

e

Input Noise Voltage

EL8171

EL8172

EL8171

EL8172

14

µV

N

P-P

10

µV

Input Noise Voltage Density

Input Noise Current Density

f = 1kHz

220

80

nV/√Hz

pA/√Hz

dB

o

i

EL8171, f = 1kHz

0.9

0.2

85

N

o

EL8172, f = 1kHz

o

CMRR @ 60Hz Input Common Mode Rejection Ratio

EL8171

EL8172

EL8171

EL8172

V

R

= 1V

,

PP

CM

= 10kΩ to V

L

CM

100

90

dB

PSRR+ @

120Hz

Power Supply Rejection Ratio (V )

V , V = ±2.5V,

dB

+

-

V

= 1V ,

SOURCE

= 10kΩ to V

PP

92

dB

R

L

CM

PSRR- @

120Hz

Power Supply Rejection Ratio (V )

EL8171

EL8172

V , V = ±2.5V,

97

92

dB

-

+

-

V

= 1V ,

SOURCE

= 10kΩ to V

PP

R

L

CM

TRANSIENT RESPONSE

SR

Slew Rate

R

= 1kΩ to GND

0.4

0.55

0.7

V/µs

L

0.35

0.7

NOTES:

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

2. V

= +5.25V max when V

= +V (device in disable state).

ENL

SUPPLY

FN6293.3

August 3, 2007

3

EL8171, EL8172

Typical Performance Curves V = 5V, V = 0V,V = 2.5V, V = V-, R = Open, unless otherwise specified.

+

-

CM

EN

L

70

60

50

40

30

20

10

90

80

70

60

50

40

30

COMMON-MODE INPUT = 1/2V+

GAIN = 10,000

GAIN = 5,000

GAIN = 1000

GAIN = 500

GAIN = 200

GAIN = 100

GAIN = 50

GAIN = 2,000

GAIN = 1,000

GAIN = 500

GAIN = 20

GAIN = 10

GAIN = 200

GAIN = 100

1

10

100

1k

10k

100k

1M

1

10

100

1k

10k

100k

1M

FREQUENCY (Hz)

FIGURE 1. EL8171 FREQUENCY RESPONSE vs CLOSED

LOOP GAIN

FIGURE 2. EL8172 FREQUENCY RESPONSE vs CLOSED

LOOP GAIN

25

20

45

40

V

= 5V

+

35

30

25

20

15

10

5

V

= 5V

+

V

= 2.4V

15

10

+

V

= 2.4V

+

A

R

C

= 100

= 10kΩ

= 10pF

A

R

C

= 10

= 10kΩ

= 10pF

V

L

F

G

V

L

F

G

5

0

R /R = 100

R

R /R = 10

R

G

= 10kΩ

= 1kΩ

= 100Ω

0

10

100

1k

10k

100k

1M

10

100

1k

10k

100k

1M

FREQUENCY (Hz)

FIGURE 3. EL8171 FREQUENCY RESPONSE vs SUPPLY

VOLTAGE

FIGURE 4. EL8172 FREQUENCY RESPONSE vs SUPPLY

VOLTAGE

50

25

820pF

470pF

2200pF

1200pF

45

40

35

30

25

20

220pF

15

100pF

820pF

56pF

A

= 10

A

= 10

V

R = 10kΩ

C

R /R = 10

R

10

5

= 10pF

C

L

= 10pF

L

R /R = 10

F

G

F

G

R

= 10kΩ

= 100Ω

10

100

1k

10k

100k

1M

100

1k

10k

100k

1M

FREQUENCY (Hz)

FIGURE 5. EL8171 FREQUENCY RESPONSE vs C

FIGURE 6. EL8172 FREQUENCY RESPONSE vs C

LOAD

FN6293.3

August 3, 2007

4

EL8171, EL8172

Typical Performance Curves V = 5V, V = 0V,V = 2.5V, V = V-, R = Open, unless otherwise specified. (Continued)

+

-

CM

EN

L

120

90

80

70

100

80

60

40

20

0

60

50

40

30

A

= 10

A = 100

V

20

10

0

-10

10

100

1k

10k

100k

1M

10

100

1k

10k

100k

1M

FREQUENCY (Hz)

FIGURE 8. EL8172 CMRR vs FREQUENCY

FIGURE 7. EL8171 CMRR vs FREQUENCY

120

100

80

60

40

20

0

100

80

60

40

20

0

PSRR+

PSRR-

A

= 10

100

V

A

= 10

100

V

10

1k

10k

100k

1M

10

1k

10k

100k

1M

FREQUENCY (Hz)

FIGURE 9. EL8171 PSRR vs FREQUENCY

FIGURE 10. EL8172 PSRR vs FREQUENCY

1400

1200

1000

800

600

400

200

0

700

600

500

400

300

200

100

0

A

= 10

100

V

A

= 100

V

1

10

1k

10k

100k

1

10

100

1k

10k

100k

FREQUENCY (Hz)

FIGURE 11. EL8171 VOLTAGE NOISE SPECTRAL DENSITY

FIGURE 12. EL8172 VOLTAGE NOISE SPECTRAL DENSITY

FN6293.3

August 3, 2007

5

EL8171, EL8172

Typical Performance Curves V = 5V, V = 0V,V = 2.5V, V = V-, R = Open, unless otherwise specified. (Continued)

+

-

CM

EN

L

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

6

5

4

3

2

1

0

A

= 100

V

A

= 10

V

1

10

100

1k

10k

100k

10k

1

10

100

1k

100k

FREQUENCY (Hz)

FIGURE 13. EL8171 CURRENT NOISE SPECTRAL DENSITY

FIGURE 14. EL8172 CURRENT NOISE SPECTRAL DENSITY

TIME (1s/DIV)

FIGURE 15. EL8171 0.1Hz TO 10Hz INPUT VOLTAGE NOISE

(GAIN = 10)

FIGURE 16. EL8172 0.1Hz TO 10Hz INPUT VOLTAGE NOISE

(GAIN = 100)

80

90

N = 1500

85

N = 1000

75

MAX

80

MAX

70

75

65

60

55

50

45

40

MEDIAN

70

MEDIAN

65

60

MIN

55

50

45

40

-40

-20

0

20

40

60

80

100

120

-40

-20

0

20

40

60

80

100

120

TEMPERATURE (°C)

FIGURE 17. EL8171 SUPPLY CURRENT ENABLED vs

TEMPERATURE, V , V = ±2.5V, V = 0V

FIGURE 18. EL8172 SUPPLY CURRENT ENABLED vs

TEMPERATURE, V , V = ±2.5V, V = 0V

+

-

IN

+

-

IN

FN6293.3

August 3, 2007

6

EL8171, EL8172

Typical Performance Curves V = 5V, V = 0V,V = 2.5V, V = V-, R = Open, unless otherwise specified. (Continued)

+

-

CM

EN

L

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

20

18

16

14

12

10

8

N = 1500

N = 1000

MAX

MEDIAN

MIN

6

4

2

0

-40

-20

0

20

40

60

80

100 120

-40

-20

0

20

40

60

80

100

120

TEMPERATURE (°C)

FIGURE 20. EL8172 SUPPLY CURRENT DISABLED vs

TEMPERATURE, V , V = ±2.5V, V = V , V = 0V

FIGURE 19. EL8171 SUPPLY CURRENT DISABLED vs

TEMPERATURE, V , V = ±2.5V, V = V , V = 0V

EN

+

-

+

IN

EN

+

-

+

IN

2.5

2.0

1.5

1.0

0.5

0

0.7

0.5

N = 1500

N = 1000

MAX

0.3

0.1

MEDIAN

-0.1

-0.3

-0.5

-0.7

-0.5

-1.0

-1.5

-2.0

MIN

40

MIN

80

-40

-20

0

20

40

60

100 120

-40

-20

0

20

60

80

100 120

TEMPERATURE (°C)

FIGURE 21. EL8171 V

vs TEMPERATURE, V , V = ±2.5V,

FIGURE 22. EL8172 V

vs TEMPERATURE, V , V = ±2.5V,

OS

+

-

OS

+

-

V

= 0V

V

= 0V

IN

0.9

0.7

2.5

2.0

1.5

1.0

0.5

0

N = 1000

N = 1500

MAX

0.5

MAX

0.3

MEDIAN

0.1

MEDIAN

-0.5

-1.0

-1.5

-2.0

-2.5

-0.1

-0.3

-0.5

-0.7

MIN

60

MIN

40

-40

-20

0

20

40

80

100 120

-40

-20

0

20

60

80

100

120

TEMPERATURE (°C)

FIGURE 23. EL8171 V

vs TEMPERATURE, V , V = ±1.2V,

FIGURE 24. EL8172 V

vs TEMPERATURE, V , V = ±1.2V,

OS + -

OS

+

-

V

= 0V

V

= 0V

IN

FN6293.3

August 3, 2007

7

EL8171, EL8172

Typical Performance Curves V = 5V, V = 0V,V = 2.5V, V = V-, R = Open, unless otherwise specified. (Continued)

+

-

CM

EN

L

140

130

120

110

100

90

140

130

120

110

100

90

N = 1500

N = 1000

MAX

MEDIAN

MIN

40

TEMPERATURE (°C)

MIN

40

TEMPERATURE (°C)

80

-40

-20

0

20

60

80

100

120

-40

-20

0

20

60

80

100

120

FIGURE 25. EL8171 CMRR vs TEMPERATURE,

= +2.5V TO -2.5V, V , V = ±2.5V

FIGURE 26. EL8172 CMRR vs TEMPERATURE,

= +2.5V TO -2.5V, V , V = ±2.5V

V

CM

+

-

+

-

140

130

120

110

100

90

140

130

120

110

100

90

N = 1500

N = 1000

MAX

MEDIAN

MIN

MEDIAN

MIN

80

70

60

-40

-20

0

20

40

60

80

100

120

-40

-20

0

20

40

60

80

100

120

TEMPERATURE (°C)

FIGURE 27. EL8171 PSRR vs TEMPERATURE,

V , V = ±1.2V TO ±2.5V

FIGURE 28. EL8172 PSRR vs TEMPERATURE,

V , V = ±1.2V TO ±2.5V

+

-

+

-

1.5

1.3

1.1

0.9

0.7

0.5

0.3

0.1

-0.1

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0

N = 1000

N = 1500

MAX

MEDIAN

MIN

-0.1

-40

-20

0

20

40

60

80

100

120

-40

-20

0

20

40

60

80

100

120

TEMPERATURE (°C)

FIGURE 29. EL8171% GAIN ERROR vs TEMPERATURE,

= 100k

FIGURE 30. EL8172% GAIN ERROR vs TEMPERATURE,

= 100k

R

L

FN6293.3

August 3, 2007

8

EL8171, EL8172

Typical Performance Curves V = 5V, V = 0V,V = 2.5V, V = V-, R = Open, unless otherwise specified. (Continued)

+

-

CM

EN

L

4.91

4.90

4.89

4.88

4.87

4.86

4.85

4.84

4.83

4.91

4.90

4.89

4.88

4.87

4.86

4.85

4.84

4.83

N = 1000

N = 1500

MAX

MEDIAN

MIN

80

MIN

80

-40

-20

0

20

40

60

100

120

-40

-20

0

20

40

60

100

120

TEMPERATURE (°C)

FIGURE 31. EL8171 V

HIGH vs TEMPERATURE,

FIGURE 32. EL8172 V

HIGH vs TEMPERATURE,

OUT

= 1k, V , V = ±2.5V

R

= 1k, V , V = ±2.5V

L

+

-

L

+

-

200

180

160

140

120

100

80

180

170

160

150

140

130

120

110

100

90

N = 1000

MAX

MEDIAN

MIN

-40

-20

0

20

40

60

80

100 120

-40

-20

0

20

40

60

80

100

120

TEMPERATURE (°C)

FIGURE 33. EL8171 V

LOW vs TEMPERATURE,

FIGURE 34. EL8172 V

LOW vs TEMPERATURE,

OUT

= 1k, V , V = ±2.5V

R

R = 1k, V , V = ±2.5V

L

+

-

L + -

0.65

0.60

0.55

0.50

0.45

0.40

0.35

0.30

0.60

0.58

0.56

0.54

0.52

0.50

0.48

0.46

0.44

0.42

0.40

MAX

N = 1500

MAX

N = 1000

MEDIAN

MIN

-40

-20

0

20

40

60

80

100

120

-40

-20

0

20

40

60

80

100

120

TEMPERATURE (°C)

FIGURE 35. EL8171 +SLEW RATE vs TEMPERATURE,

INPUT = ±0.015V @ GAIN + 100

FIGURE 36. EL8172 +SLEW RATE vs TEMPERATURE,

INPUT = ±0.015V @ GAIN + 100

FN6293.3

August 3, 2007

9

EL8171, EL8172

Typical Performance Curves V = 5V, V = 0V,V = 2.5V, V = V-, R = Open, unless otherwise specified. (Continued)

+

-

CM

EN

L

0.65

0.70

0.65

0.60

0.55

0.50

0.45

0.40

0.35

0.30

N = 1000

MAX

N = 1500

MAX

0.60

0.55

0.50

0.45

0.40

MEDIAN

MIN

-40

-20

0

20

40

60

80

100

120

-40

-20

0

20

40

60

80

100

120

TEMPERATURE (°C)

FIGURE 38. EL8172 -SLEW RATE vs TEMPERATURE,

INPUT = ±0.015V @ GAIN + 100

FIGURE 37. EL8171 -SLEW RATE vs TEMPERATURE,

INPUT = ±0.015V @ GAIN + 100

Pin Descriptions

EL8171/EL8172

PIN NAME

EQUIVALENT CIRCUIT

PIN FUNCTION

1

EN

Circuit 2

Active LOW logic pins. When pulled above 2V, the corresponding channel turns off

and OUT is high impedance. A channel is enabled when pulled below 0.8V. Built

in pull downs define each EN pin LOW when left floating.

2

3

IN-

Circuit 1A, Circuit 1B

High impedance input terminals. EL8172 input circuit is shown in Circuit 1A, and

the EL8171 input circuit is shown in Circuit 1B. EL8171: to avoid offset drift, it is

recommended that the terminals are not overdriven beyond 1V and the input

current must never exceed 5mA.

IN+

4

5

8

V-

Circuit 4

Negative supply terminal.

FB-

FB+

Circuit 1A, Circuit 1B

High impedance feedback terminals. EL8172 input circuit is shown in Circuit 1A,

and the EL8171 input circuit is shown in Circuit 1B. EL8171: to avoid offset drift, it

is recommended that the terminals are not overdriven beyond 1V and the input

current must never exceed 5mA.

7

6

V+

Circuit 4

Circuit 3

Positive supply terminal.

Output Voltage.

VOUT

V+

CAPACITIVELY

COUPLED

ESD CLAMP

IN+

FB+

IN-

FB-

LOGIC

OUT

V-

CIRCUIT 1A

CIRCUIT 2

CIRCUIT 3

CIRCUIT 4

V+

IN+

IN-

FB+

FB-

V-

CIRCUIT 1B

FN6293.3

August 3, 2007

10

EL8171, EL8172

Output Stage and Output Voltage Range

A pair of complementary MOSFET devices drive the output

to within a few mV of the supply rails. At a 100kΩ load,

the PMOS sources current and pulls the output up to 4mV

below the positive supply, while the NMOS sinks current and

pulls the output down to 4mV above the negative supply, or

ground in the case of a single supply operation. The current

sinking and sourcing capability of the EL8171 and EL8172

are internally limited to less than 35mA.

Description of Operation and Application

Information

V

OUT

Product Description

The EL8171 and EL8172 are micropower instrumentation

amplifiers (in-amps) which deliver rail-to-rail input amplification

and rail-to-rail output swing on a single 2.4V to 5.5V supply. The

EL8171 and EL8172 also deliver excellent DC and AC

specifications while consuming only 65µA typical supply

current. Because EL8171 and EL8172 provide an independent

pair of feedback terminals to set the gain and to adjust the

output level, these in-amps achieve high common-mode

rejection ratio regardless of the tolerance of the gain setting

resistors. The EL8171 is internally compensated for a minimum

closed loop gain of 10 or greater, well suited for moderate to

high gains. For higher gains, the EL8172 is internally

compensated for a minimum gain of 100. An EN pin is used to

reduce power consumption, typically 4.5µA, while the

instrumentation amplifier is disabled.

Gain Setting

V

, the potential difference across IN+ and IN-, is replicated

IN

(less the input offset voltage) across FB+ and FB-. The

obsession of the EL8171 and EL8172 in-amp is to maintain

the differential voltage across FB+ and FB- equal to IN+ and

IN-; (FB+ - FB-) = (IN+ - IN-). Consequently, the transfer

function can be derived. The gain of the EL8171 and EL8172

is set by two external resistors, the feedback resistor R , and

F

the gain resistor R .

G

2.4V TO 5.5V

EN

Input Protection

7

1

All input and feedback terminals of the EL8171 and EL8172

have internal ESD protection diodes to both positive and

negative supply rails, limiting the input voltage to within one

diode drop beyond the supply rails. The inverting inputs and

FB- inputs have ESD diodes to the V-rail, and the non-inverting

inputs and FB+ terminals have ESD diodes to the V+ rail. The

EL8172 has additional back-to-back diodes across the input

terminals and also across the feedback terminals. If overdriving

the inputs is necessary, the external input current must never

exceed 5mA. On the other hand, the EL8171 has no clamps to

limit the differential voltage on the input terminals allowing

higher differential input voltages at lower gain applications. It is

recommended however, that the input terminals of the EL8171

are not overdriven beyond 1V to avoid offset drift. An external

series resistor may be used as an external protection to limit

excessive external voltage and current from damaging the

inputs.

VIN/2

V+

EN

2

3

8

5

IN+

IN-

+

-

6

VOUT

EL8171/2

FB+

FB-

+

-

VCM

V-

4

RG

RF

FIGURE 39. CIRCUIT 1 - GAIN IS BY EXTERNAL RESISTORS

R

AND R

G

F

R

⎛

⎜

⎝

⎞

F

(EQ. 1)

--------

V

=

1 +

V

⎟

⎠

OUT

IN

R

G

In Figure 39, the FB+ pin and one end of resistor RG are

connected to GND. With this configuration, Equation 1 is

Input Stage and Input Voltage Range

only true for a positive swing in V ; negative input swings

will be ignored and the output will be at ground.

The input terminals (IN+ and IN-) of the EL8171 and EL8172

are single differential pair P-MOSFET devices aided by an

Input Range Enhancement Circuit (IREC) to increase the

headroom of operation of the common-mode input voltage.

The feedback terminals (FB+ and FB-) also have a similar

topology. As a result, the input common-mode voltage range

of both the EL8171 and EL8172 is rail-to-rail. These in-amps

are able to handle input voltages that are at or slightly

beyond the supply and ground making these in-amps well

suited for single 5V or 3.3V low voltage supply systems.

There is no need to move the common-mode input of the in-

amps to achieve symmetrical input voltage.

IN

Reference Connection

Unlike a three-op amp instrumentation amplifier, a finite

series resistance seen at the REF terminal does not degrade

the EL8171 and EL8172's high CMRR performance,

eliminating the need for an additional external buffer

amplifier. Circuit 2 (Figure 40) uses the FB+ pin to provide a

high impedance REF terminal.

FN6293.3

August 3, 2007

11

EL8171, EL8172

External Resistor Mismatches

2.4V TO 5.5V

EN

Because of the independent pair of feedback terminals

provided by the EL8171 and EL8172, the CMRR is not

degraded by any resistor mismatches. Hence, unlike a three op

amp and especially a two op amp in-amp, the EL8171 and

EL8172 reduce the cost of external components by allowing the

use of 1% or more tolerance resistors without sacrificing CMRR

performance. The EL8171 and EL8172 CMRR will be

maintained regardless of the tolerance of the resistors used.

7

1

VIN/2

V+

EN

2

3

8

5

IN+

IN-

+

-

6

VOUT

EL8171/2

FB+

FB-

+

-

VCM

V-

4

2.4V TO 5.5V

R1

REF

Gain Error and Accuracy

R2

RG

RF

The EL8172 has a Gain Error (EG) of 0.2% typical. The

EL8171 has an EG of 0.15% typical. The gain error indicated

in the “Electrical Specifications” table on page 2 is the inherent

gain error of the EL8171 and EL8172 and does not include

the gain error contributed by the resistors. There is an

additional gain error due to the tolerance of the resistors used.

The resulting non-ideal transfer function effectively becomes:

FIGURE 40. CIRCUIT 2 - GAIN SETTING AND REFERENCE

CONNECTION

R

F

R

G

⎛

⎜

⎝

⎞

⎟

⎠

⎛

⎞

⎟

⎠

F

(EQ. 2)

--------

V

=

1 +

(V ) + 1 +

(V

)

REF

⎜

OUT

IN

R

G

⎝

R

⎛

⎜

⎝

⎞

⎟

⎠

The FB+ pin is used as a REF terminal to center or to adjust

the output. Because the FB+ pin is a high impedance input,

an economical resistor divider can be used to set the voltage

at the REF terminal without degrading or affecting the CMRR

performance. Any voltage applied to the REF terminal will

F

--------

V

=

1 +

× [1 – (E

+ E

+ E )] × V

RF G IN

(EQ. 4)

OUT

RG

R

G

Where:

E

= Tolerance of R

RG

RF

G

shift V

by V

times the closed loop gain, which is set

OUT

REF

F

by resistors R and R . See Circuit 2 (Figure 40). Note that

F

G

= Gain Error of the EL8171 or EL8172

any noise or unwanted signals on the reference supply will

be amplified at the output according to Equation 2.

The term [1-(E

RG

+E +E )] is the deviation from the

G

RF

theoretical gain. Thus, (E

+E +E ) is the total gain

The FB+ pin can also be connected to the other end of resistor,

RG

RF

G

error. For example, if 1% resistors are used for the EL8171,

the total gain error would be:

R . See Circuit 3 (Figure 41). Keeping the basic concept that

G

the EL8171 and EL8172 in-amps maintain constant differential

voltage across the input terminals and feedback terminals (IN+

- IN- = FB+ - FB-), the transfer function of Circuit 3 can be

derived. Note that the VREF gain term is eliminated and

susceptibility to external noise is reduced, however the VREF

source must be capable of sourcing or sinking the feedback

= ±(E

+ E

+ E (typical))

RF G

RG

(EQ. 5)

= ±(0.01 + 0.01 + 0.003)

= ±2.3%

Disable/Power-Down

current from V

OUT

through R and R .

F

G

The EL8171 and EL8172 can be powered down reducing

the supply current to typically 4.5µA. When disabled, the

output is in a high impedance state. The active low EN bar

pin has an internal pull-down and hence can be left floating

and the in-amp enabled by default. When the EN bar is

connected to an external logic, the in-amp will power down

when EN bar is pulled above 2V, and will power on when EN

bar is pulled below 0.8V.

2.4V TO 5.5V

EN

7

1

VIN/2

V+

EN

2

3

8

5

IN+

+

IN-

-

VIN/2

6

VOUT

EL8171/2

FB+

FB-

+

-

VCM

V-

4

RG

RF

VREF

FIGURE 41. CIRCUIT 3 - REFERENCE CONNECTION WITH AN

AVAILABLE VREF

R

⎛

⎜

⎝

⎞

⎟

⎠

F

(EQ. 3)

--------

V

=

1 +

(V ) + (V

)

REF

OUT

IN

R

G

FN6293.3

August 3, 2007

12

EL8171, EL8172

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

) for all applications

JMAX

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 6:

T

= T

+ (θ xPD

)

MAXTOTAL

(EQ. 6)

JMAX

MAX

JA

where:

• P

is the sum of the maximum power

MAX

for each amplifier can be calculated as shown in

DMAXTOTAL

dissipation of each amplifier in the package (PD

)

• PD

MAX

Equation 7:

V

OUTMAX

R

L

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

PD

= 2*V × I

+ (V - V ) ×

OUTMAX

MAX

S

SMAX

S

(EQ. 7)

where:

• T

MAX

= Maximum ambient temperature

• θ = Thermal resistance of the package

JA

• PD

MAX

= Maximum power dissipation of 1 amplifier

• V = Supply voltage (Magnitude of V and V )

S

+

-

• I

= Maximum supply current of 1 amplifier

MAX

• V

OUTMAX

= Maximum output voltage swing of the

application

• R = Load resistance

L

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

FN6293.3

August 3, 2007

13

EL8171, EL8172

Small Outline Package Family (SO)

A

D

h X 45°

(N/2)+1

N

A

PIN #1

I.D. MARK

E1

E

c

SEE DETAIL “X”

1

(N/2)

B

L1

0.010 M

C A B

e

H

C

A2

A1

GAUGE

PLANE

SEATING

PLANE

0.010

L

4° ±4°

0.004 C

b

0.010 M

C

A

B

DETAIL X

MDP0027

SMALL OUTLINE PACKAGE FAMILY (SO)

INCHES

SO16

(0.150”)

SO16 (0.300”)

(SOL-16)

SO20

SO24

(SOL-24)

SO28

(SOL-28)

SYMBOL

SO-8

0.068

0.006

0.057

0.017

0.009

0.193

0.236

0.154

0.050

0.025

0.041

0.013

8

SO-14

0.068

0.006

0.057

0.017

0.009

0.341

0.236

0.154

0.050

0.025

0.041

0.013

14

(SOL-20)

0.104

0.007

0.092

0.017

0.011

0.504

0.406

0.295

0.050

0.030

0.056

0.020

20

TOLERANCE

MAX

NOTES

A

A1

A2

b

0.068

0.006

0.057

0.017

0.009

0.390

0.236

0.154

0.050

0.025

0.041

0.013

16

0.104

0.007

0.092

0.017

0.011

0.406

0.295

0.050

0.030

0.056

0.020

16

0.104

0.007

0.092

0.017

0.011

0.606

0.406

0.295

0.050

0.030

0.056

0.020

24

0.104

0.007

0.092

0.017

0.011

0.704

0.406

0.295

0.050

0.030

0.056

0.020

28

-

±0.003

±0.002

±0.003

±0.001

±0.004

±0.008

±0.004

Basic

-

c

-

D

1, 3

E

-

E1

e

2, 3

-

L

±0.009

Basic

-

L1

h

-

Reference

-

N

-

Rev. M 2/07

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

FN6293.3

August 3, 2007

14


型号：	EL8172FSZ
厂家：	Intersil
描述：	Micropower, Single Supply, Rail-to-Rail Input-Output Instrumentation Amplifiers 微功耗，单电源，轨到轨输入输出仪表放大器仪表放大器
文件：	总14页 (文件大小：643K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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