Texas Instruments INA149 User manual

User's Guide

SBOU119–November 2011

INA149EVM

This user's guide describes the characteristics, operation, and use of the evaluation module (EVM) for the

INA149. The EVM is designed to evaluate the performance of the device in both single and dual-supply

configurations. This document also includes the schematic, printed circuit board (PCB) layout, and a bill of

materials (BOM). Throughout this document the terms evaluation board,evaluation module, and EVM are

synonymous with the INA149EVM.

WARNING

Danger: HIGH VOLTAGE! This evaluation board is intended for

professional use only. It has exposed high voltages. Do not

operate this board without proper high-voltage/high-current safety

practices. Read Section 1.3 before using the EVM.

Contents

1 Introduction and Warnings ................................................................................................. 2

2 INA149EVM Hardware ..................................................................................................... 4

3 Bill of Materials ............................................................................................................. 10

4 Related Documentation from Texas Instruments ..................................................................... 10

List of Figures

1 INA149EVM.................................................................................................................. 2

2 INA149EVM Input/Output Schematic..................................................................................... 4

3 INA149EVM Reference Voltage Schematic............................................................................. 5

4 INA149EVM Power Schematic............................................................................................ 6

5 INA149EVM Complete Schematic........................................................................................ 7

6 INA149EVM PCB Layout .................................................................................................. 9

SBOU119–November 2011 INA149EVM

Introduction and Warnings

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1 Introduction and Warnings

1.1 INA149

The INA149 is a precision unity-gain difference amplifier with a very high input common-mode voltage

range (±275 V). It is composed of a precision operational amplifier and an integrated thin-film resistor

network. The topology allows the device to buffer small differential signals in the presence of a large

common-mode voltage. The device is pin-compatible with the INA117 and other industry standard

devices. It is available in an SO-8 package.

1.2 INA149EVM

The INA149EVM is intended to provide basic functional evaluation of the INA149. It provides the following

features:

•Easy access to pertinent nodes with test points and terminal blocks

•Convenient input and output filtering

•Versatile pad for evaluation in current/sensing applications

•Reverse supply and overvoltage protection

•Advanced evaluation with prototype areas and SMA/SMB connector footprints

•Footprints for providing a flexible reference voltage

A picture of the INA149EVM is shown in Figure 1

Figure 1. INA149EVM

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Introduction and Warnings

1.3 Evaluation Module Limitations &Warnings

As a result of the high common-mode input voltage rating of the INA149, evaluation of the device often

involves high-voltage operation. As a difference amplifier, it may also be used in current-sensing

applications. In addition to voltage and current limitations, proper electrostatic discharge precautions are

recommended.

1.3.1 High Voltage

The common-mode input voltage rating of the INA149 is ±275 V. When using the device and EVM under

such circumstances, all proper safety practices must be followed. Do not apply more than ±275 V

common-mode.

1.3.2 High Current

For current-sensing applications, an unpopulated pad is provided for a sense resistor (RSENSE). The

sense resistor trace has a maximum current rating of 5 A. Ensure that the power rating of the sense

resistor is sufficient for the application.

1.3.3 Electrostatic Discharge

Many of the components on the INA149EVM are susceptible to damage by electrostatic discharge (ESD).

Customers are advised to observe proper ESD handling precautions when unpacking and handling the

EVM, including the use of a grounded wrist strap at an approved ESD workstation.

SBOU119–November 2011 INA149EVM

INA149

19kΩ

380kΩ

20kΩ

380kΩ

REF

-IN

V-

+IN

REF

OUT

V+

VOUT

0 Ω

-IN

+IN

RSENSE

0 Ω

CON_OUT

CON1

CON2

GND

C1R12

cm-c

⋅⋅π

( )











+⋅+⋅π

−

C2R2R12

dmc

⋅⋅π

−

INA149EVM Hardware

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2 INA149EVM Hardware

This section discusses the INA149EVM hardware schematics, PCB layout, prototype area, and jumpers.

2.1 Input/Output Schematic

The input/output section of the schematic is shown in Figure 2. The input signal is applied through terminal

block T2 and the output can be measured with test point VOUT. Alternately, SMA or SMB connectors can

be populated in the provided footprints: CON1, CON2, and CON_OUT. Input filtering can be applied with

R1, R2, and C1-3. The common-mode and differential-mode cutoff frequency equations are given in

Equation 1 and Equation 2, respectively. It is recommended to make C2 approximately ten times larger

than C1 and C3. The equations assume R1 is equivalent to R2 and C1 is equivalent to C3. Note that any

of the capacitors and resistors selected must be rated for the inputs being applied. An output filter can

also be implemented with R6 and C6. The corresponding cutoff frequency equation is given in Equation 3.

Finally, a versatile pad is provided for evaluation in current-sensing applications. RSENSE can

accommodate through-hole resistors or a surface-mount sense resistor from 0603 to 1206 in size. The

trace width provides for evaluation of load currents up to 5 A.

Figure 2. INA149EVM Input/Output Schematic

Common-mode cutoff frequency:

(1)

Differential-mode cutoff frequency:

(2)

Output filter cutoff frequency:

(3)

4INA149EVM SBOU119–November 2011

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INA149

19kΩ

380kΩ

20kΩ

380kΩ

REF

-IN

V-

+IN

REF

OUT

V+

JMP4

GND

JMP3 JMP2

1 2 3 123

REFB REFA

GND

REFV-

REFV+

V-

V+

GND

REF

SO-8

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INA149EVM Hardware

2.2 Reference Voltage Schematic

Figure 3 shows that the reference voltage can be applied to the INA149 in a variety of ways. The INA149

has two pins for reference voltages: REFA, REFB. Most applications require REFA and REFB to be

shorted. This functionality is accomplished with JMP4. In dual-supply applications, the reference voltages

are typically connected to ground. Connecting pins 2 and 3 of JMP2 and JPM3 accommodate this

configuration. For single-supply applications, It is often required to connect the reference voltages to

mid-supply. This can be accomplished by either applying a voltage directly to test point REFA (or test

point REFB) and shorting JMP4, or using the resistive divider created by R3 and R4. If a matched

precision resistor network is desired, a SOT-23 pad (R9) is located on the bottom of the board. When

using a resistor divider, however, the voltage must be buffered to ensure good common-mode rejection

(CMR). U2 is intended for a standard pinout operational amplifier in an SO-8 package. If U2 is to be

another supply can be connected to the REFV+ and REFV–test points. Recommendations for this

operational amplifier include the OPA376,OPA330, and OPA277.

Figure 3. INA149EVM Reference Voltage Schematic

SBOU119–November 2011 INA149EVM

INA149

19kΩ

380kΩ

20kΩ

380kΩ

REF

-IN

V-

+IN

REF

OUT

V+

V-

GND

10µF 10µF

10µFV+V-

JMP1

C32 C31

C33

D2D3

0.1µF

GND

C11

INA149EVM Hardware

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2.3 Power Schematic

The power schematic is depicted in Figure 4. Power is applied to the INA149EVM through terminal block

T1. Reverse supply protection diodes (D2, D3) protect the device from accidental switching of the positive

and negative supply voltages. As a consequence, each supply voltage should be increased by one diode

voltage drop. Test points V+ and V–have been provided to ensure the desired supply voltage is being

applied to the device. D1 is a transient voltage suppressor (TVS) diode. D1 aids in protecting the INA149

from supply voltages in excess of 36 V (±18 V). JMP1 allows the user to short the negative supply voltage

(V–) to ground, which provides a simple method for operating the device with a single supply. Do not

shunt JMP1 during dual-supply operation because this action will short the negative supply to ground.

Capacitors C2 and C11 are placed as close to the device as possible to provide power-supply decoupling.

Figure 4. INA149EVM Power Schematic

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Do not populate

V- = GND

Reverse Standoff = 40-44.4

Prototyping Space

Terminal Block

JMP4 shorts REFA and REFB

DNI

DNIDNI

DNI

GND Test Points

2-IN

+IN

OUT

V+

4V-

8NC

5NC

1NC

.1uF

REF_B

2-IN

+IN

4V-

V+

VOUT

REF_A

INA149_SO8

RESISTOR_TH

C12

.1uF

C11

.1uF

R_SENSE

JMP3

CON_OUT

REF

+IN -IN

V-

TP1

V+

TP1

JMP1

1V+

2V-

3GND

PROTOSPACE

CON2

CON1

TP2

TP1

0ohm

JMP2

JMP4

JUMP2

REFB

TP1

REFA

TP1

TP3

TP1

VOUT

TP1

0ohm

REFV-

REFV+

C31

10uF

C32

10uF

C33

10uF

V- V+

REFB

V+

V-

REFA

REF

REFA

REFB

REF

REFA

REFB

V+

V-

V+

V-

V+

V-

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INA149EVM Hardware

2.4 Complete Schematic

Figure 5 depicts the complete INA149EVM schematic.

Figure 5. INA149EVM Complete Schematic

SBOU119–November 2011 INA149EVM

INA149EVM Hardware

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2.5 Prototype Area

For flexible evaluation, the INA149EVM has a small prototyping area. This area is intended to be used

with devices mounted on 8-pin DIP adapter boards. Power can be readily applied using the nearby V+,

V–, and GND rails.

2.6 Jumper Table

There are four jumpers located on the INA149EVM. Their functions are summarized in Table 1.

Table 1. Jumpers

Jumper Function

JMP1 This jumper shorts the V–power rail to ground. It allows a single supply to be used instead of a dual supply.

JMP2 This jumper allows the REFA pin on the INA149 to be connected to ground or the external reference op amp. The shunt on the jumper

can be removed as well to allow an external reference to be attached to the REFA test point.

JMP3 This jumper allows the REFB pin on the INA149 to be connected to ground or the external reference op amp. The shunt on the jumper

can be removed as well to allow an external reference to be attached to the REFB test point.

JMP4 This jumper shorts the REFA and REFB pins together. When shorting this jumper, make sure JMP2 and JMP3 are not in conflicting

positions.

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INA149EVM Hardware

2.7 PCB Layout

Figure 6 depicts the PCB layout.

Figure 6. INA149EVM PCB Layout

NOTE: Board layout is not to scale. This figure is intended to show how the board is laid out; it is not

intended to be used for manufacturing INA149EVM PCBs.

SBOU119–November 2011 INA149EVM

Bill of Materials

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3 Bill of Materials

Table 2 the bill of materials used for the INA149EVM. It also lists examples of optional components.

Table 2. INA149EVM Bill of Materials

Count RefDes Value Description Part Number MFR

1 U1 N/A INA149, SO-8 INA149 Texas

Instruments

2 C11-12 0.1µF Capacitor, .10µF, 50V, X7R, 0603 06035C104JAT2A AVX Corporation

3 C31-33 10µF Capacitor, 4.7µF, 50V, X7S, 1210 C3225X7S1H106M TDK Corporation

1 D1 N/A Diode, TVS, 36V, 400W Bi-directional, SMD SMAJ36CA Bourns Inc.

2 D2-3 N/A Diode, Schottky, 40V, SMB MBRS2040LT3G On

Semiconductor

2 T1-2 N/A Terminal Block, 3.5mm, 3 Position 1984620 Phoenix Contact

1 R6 0ohm Resistor, 0Ohm, 0603 RC0603JR-070RL Yageo

2 R1-2 0ohm Resistor, 0Ohm, 1206 RC1206JR-070RL Yageo

2 JMP2-3 3POS 3 Position Connection Header .100"TSW-102-07-G-S Samtec

2 JMP1,4 2POS 2 Position Connection Header .100"TSW-102-07-G-S Samtec

10 REFA, REFB, N/A Through-hole Test Points 5009 Keystone

3xGND, V+, V–, Electronics

VOUT

4 N/A N/A Bumpon, .375X.135, Black SJ61A8 3M

4 N/A N/A Shunt w/Handle, 2 Position 881545-2 TE Connectivity

Not Installed C1-3 N/A Capacitor, 0603-1206 or through–hole

Not Installed C4-6, C8 N/A Capacitor, 0603

Not Installed RSENSE N/A Sense Resistor, 0603-1206 or through–hole

Not Installed R3-R4 N/A Resistor, 0603-1206 or through-hole

Not Installed R5, R7-8 N/A Resistor, 0603

Not Installed REF, REFV+, N/A Through-hole Test Point 5009 Keystone

REFV–, +IN, –IN Electronics

Not Installed U2 N/A Op-Amp, SO-8

Not Installed CON1, CON2, N/A SMA/SMB Edge mounted connector

CON_OUT

4 Related Documentation from Texas Instruments

The following documents provide information regarding Texas Instruments' integrated circuits and support

tools for the INA149EVM. This user's guide is available from the TI web site under literature number

SBOU119. Any letter appended to the literature number corresponds to the document revision that is

current at the time of the writing of this document. Newer revisions may be available from the TI web site,

or call the Texas Instruments' Literature Response Center at (800) 477-8924 or the Product Information

Center at (972) 644-5580. When ordering, identify the document by both title and literature number.

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