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
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Introduction and Warnings www.ti.com
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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www.ti.com 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.
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INA149
U1
+
19kΩ
380kΩ
20kΩ
380kΩ
380kΩ
B
REF
-IN
V-
+IN
A
REF
OUT
V
V+
NC
R6
VOUT
C6
C2
C1
C3
0 Ω
0 Ω
T2
-IN
+IN
R2
R1
RSENSE
0 Ω
CON_OUT
CON1
CON2
GND
C1R12
1
f
cm-c
⋅⋅π
=
( )





+⋅+⋅π
=
−
2
C1
C2R2R12
1
f
dmc
C6
R6
2
1
f
oc
⋅⋅π
=
−
INA149EVM Hardware www.ti.com
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)
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INA149
U1
+
19kΩ
380kΩ
20kΩ
380kΩ
380kΩ
B
REF
-IN
V-
+IN
A
REF
OUT
V
V+
NC
JMP4
GND
JMP3 JMP2
1 2 3 123
REFB REFA
1
2
U2
3
4
8
7
6
5
+
GND
GND
C5
C4
REFV-
REFV+
R8
R7
R4
R3
V-
V+
V+
R5
C8
GND
REF
SO-8
R9
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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
powered by the V+ and V–supplies, R7 and R8 should be populated with 0-Ωresistors; otherwise,
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
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INA149
U1
+
19kΩ
380kΩ
20kΩ
380kΩ
380kΩ
B
REF
-IN
V-
+IN
A
REF
OUT
V
V+
NC
T1
V+
V-
GND
GND
10µF 10µF
10µFV+V-
JMP1
C32 C31
C33
D1
D2D3
0.1µF
0.1µF
GND
GND
C2
C11
INA149EVM Hardware www.ti.com
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
DNI
DNI
DNI
DNI
GND Test Points
R1
R2
C1
C2
C3
1
2
3
T1
2-IN
3
+IN
6
OUT
7
V+
4V-
8NC
5NC
1NC
U2
C4
.1uF
C5
.1uF
1
REF_B
2-IN
3
+IN
4V-
8
NC
7
V+
6
VOUT
5
REF_A
U1
INA149_SO8
R3
RESISTOR_TH
R4
RESISTOR_TH
C8
C12
.1uF
C11
.1uF
R_SENSE
C6
1
2
3
JMP3
JMP3
2
1
CON_OUT
REF
+IN -IN
V-
TP1
V+
TP1
TP1
TP1
D1
JMP1
1V+
2V-
3GND
PROTOSPACE
2
1
CON2
2
1
CON1
TP2
TP1
12
R5
0ohm
12
R6
0ohm
1
2
3
JMP2
JMP4
JUMP2
REFB
TP1
REFA
TP1
TP3
TP1
VOUT
TP1
D2
D3
1
2
3
T2
12
R7
0ohm
12
R8
0ohm
REFV-
REFV+
+
C31
10uF
+
C32
10uF
+
C33
10uF
R9
V- V+
REFB
V+
V-
REFA
REF
REFA
REFB
REF
REF
REFA
REFB
V+
V-
V+
V-
V-
V+
V+
V-
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2.4 Complete Schematic
Figure 5 depicts the complete INA149EVM schematic.
Figure 5. INA149EVM Complete Schematic
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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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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.
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Bill of Materials www.ti.com
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 [phone] or the Product Information
Center at [phone]. When ordering, identify the document by both title and literature number.
Related Documentation
Document Literature Number
INA149 Product Data Sheet SBOS579
OPA376 Product Data Sheet SBOS406
OPA277 Product Data Sheet SBOS079
OPA330 Product Data Sheet SBOS432
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