Texas Instruments LMP2021MAEVAL - Bridge Sensor Instrumentation Amp Evaluation Board (Rev. A) User's Guide

User's Guide

SNOA537A – December 2008 – Revised April 2013

AN–1932 LMP2021MAEVAL - Bridge Sensor

Instrumentation Amplifier Evaluation Board

1

2

J3

J4

J5

J7

Introduction

The LMP2021MAEVAL instrumentation amplifier evaluation board is configured as a differential-in, differential-out amplifier using the LMP2021. Also included is a precision reference and buffer to drive a bridge sensor. The board is set up to be used with the ADC141S626 evaluation board (part number:

ADC141S626EB).

Power

Connect to the positive supply.

Connect to ground.

If using dual supplies connect to the negative supply. If using a single supply short J5 to ground.

Pin 1 of J2 can be used to power the ADC141S626EB evaluation board, which requires +5 V. If J3 is +5 V, JP3 can be shorted to provide +5 V to the ADC141S626EB evaluation board. If J3 is not +5 V, leave JP3 open and connect +5 V to J7.

3

4

5

Input Signal and Bridge Excitation

J1 is used to power the bridge sensor and input the signal from the bridge to the amplifier. The LM4120

(U4) provides a precision +5 V reference. This is buffered by the LMP7741 (U5) and supplied on pin 1 of

J1 to power the bridge sensor. The bottom of the bridge sensor can be connected to pin 2, which is connected to ground. The outputs of the bridge sensor can be connected to pins 3 and 5 of J1.

Output Signal

The output of the amplifier is available on pins 3 and 5 of J2. This connector is pin-to-pin compatible with the input connector of the ADC141S626EB evaluation board.

Amplifier Gain

The gain of the amplifier is set using R1, R10, R11, and R12. If R11 = R12, the gain of the amplifier is 1 +

(2R11)/(R1||R10).

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SNOA537A – December 2008 – Revised April 2013

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AN–1932 LMP2021MAEVAL - Bridge Sensor Instrumentation Amplifier

Evaluation Board

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1

Amplifier Gain

J6

SMA

V

+CM

V

-CM

J1

1

Vb

GND

2

3

+

4

GND

5

-

6

GND

J8

SMA

V-

C8

0.1 P F

C13

0.1 P F

V+

R6

1k

C9

0.1 P F

1

C1

0.1 P F

C2

0.1 P F

5

-

V+

LMP7741 U1

4

3

V-

+

2

C4

0.1 P F

V-

3

2

4

+

V-

LMP2021 U2

V+

-

7

C5

0.1 P F

6

C6

0.1 P F

R2

0

C7

0.1 P F

V+

R11

R1

NC

R7

Vref

0

R10

150

10k

C18

0.1 P F

C19

0.1 P F

R12

V+

10k

C12

NC

R17

1k

C21

0.1 P F

C10

0.1 P F

2

3

-

V+

7

LMP2021 U3

C23

0.1 P F

6

+

V-

4

C11

0.1 P F

V-

Figure 1. Schematic

R3

0

Vref

C16

0.47 P F

5

OUT

LM4120AIM5-5.0

U4

IN

4

V+

EN

3

C17

0.1 P F

VADC

4

5

J2

1

2

3

VADC

GND

IN+

GND

INwww.ti.com

J7

+5V

J3

V+

J4

GND

J5

V-

+

C20

6.8 P F

C22

0.1 P F

VADC

JP3

C24

C25

0.1 P F

C14

0.1 P F

C15

V+

6.8 P F

C3

0.1 P F

6.8 P F

V-

2 AN–1932 LMP2021MAEVAL - Bridge Sensor Instrumentation Amplifier

Evaluation Board

SNOA537A – December 2008 – Revised April 2013

Copyright © 2008–2013, Texas Instruments Incorporated

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Amplifier Gain

Figure 2. PCB Top

Figure 3. PCB Bottom

SNOA537A – December 2008 – Revised April 2013

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AN–1932 LMP2021MAEVAL - Bridge Sensor Instrumentation Amplifier

Evaluation Board

Copyright © 2008–2013, Texas Instruments Incorporated

3

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