Texas Instruments INA185EVM User manual

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INA185EVM
User's Guide
SBOU167–March 2019
INA185EVM
This user’s guide describes the characteristics, operation, and use of the INA185 evaluation module
(EVM). This EVM is designed to evaluate the performance of the INA185A1, INA185A2, INA185A3, and
INA185A4 voltage output current-shunt monitors in a variety of configurations. Throughout this document,
the terms evaluation board, evaluation module, and EVM are synonymous with the INA185EVM. This
document includes a schematic, reference printed-circuit board (PCB) layouts, and a complete bill of
materials.

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INA185EVM
Contents
1 Overview...................................................................................................................... 3
2 Hardware...................................................................................................................... 4
3 Quick Start Setup and Use ................................................................................................. 4
4 Circuitry ....................................................................................................................... 5
5 Reference Voltage Setup................................................................................................... 6
6 Schematic, PCB Layout, and Bill of Materials ........................................................................... 7
List of Figures
1 INA185EVM Schematic..................................................................................................... 7
2 INA185EVM Top Overlay................................................................................................... 8
3 INA185EVM Bottom Overlay............................................................................................... 8
4 INA185EVM Top Solder Mask............................................................................................. 8
5 INA185EVM Top Layer ..................................................................................................... 8
6 INA185EVM Bottom Layer ................................................................................................. 8
7 INA185EVM Bottom Solder Mask ......................................................................................... 8
8 INA185EVM Drill Drawing .................................................................................................. 9
List of Tables
1 INA185Ax Gain Option Summary ......................................................................................... 3
2 INA185EVM Kit Contents................................................................................................... 3
3 Related Documentation..................................................................................................... 3
4 Bill of Materials ............................................................................................................. 10
Trademarks
All trademarks are the property of their respective owners.

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INA185EVM
1 Overview
The INA185 current-shunt monitor (also called current-sense amplifier) can sense voltage drops across
shunts at common-mode voltages from –0.2 V to +26 V, independent of the supply voltage. Four fixed
gain options are available: 20 V/V, 50 V/V, 100 V/V, and 200 V/V. The INA185 has a reference pin that
enables bidirectional current measurements. The device operates from a single 2.7-V to 5.5-V power
supply, drawing a maximum of 260 μA of supply current per amplifier channel.
The INA185 devices are currently available in a SOT-563 surface-mount package. Table 1 lists the
available gain options.
Table 1. INA185Ax Gain Option Summary
PRODUCT GAIN (V/V)
INA185A1 20
INA185A2 50
INA185A3 100
INA185A4 200
1.1 Kit Contents
Table 2 lists the contents of the INA185EVM kit. Contact the nearest Texas Instruments Product
Information Center if any components are missing. TI highly recommends checking the INA185 family
product folder on the TI website at www.ti.com for further information regarding this product.
Table 2. INA185EVM Kit Contents
ITEM QUANTITY
INA185EVM Test Board 1
1.2 Related Documentation From Texas Instruments
The following document provides information regarding TI's integrated circuits used in the assembly of the
INA185EVM. This user's guide is available from the TI website under literature number (SBOU167). 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 are available from www.ti.com or 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.
Table 3. Related Documentation
DOCUMENT LITERATURE NUMBER
INA185 Product data sheet SBOS378

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2 Hardware
The INA185 is an integrated, op amp-based current sense circuit that provides ease of use and high
performance. The INA185EVM is intended to provide basic functional evaluation of this device family. The
board layout is neither intended to be a model for the target circuit, nor is it laid out for electromagnetic
compatibility (EMC) testing. The INA185EVM consists of one PCB that can be cut into four individual
PCBs segments, one for each of the four device gain options.
2.1 Features
The layout of the INA185EVM printed-circuit board (PCB) is designed to provide the following features:
• Evaluation of all gain options for the INA185
• Ease of access to device pins with test points
• Capability to evaluate high-side and low-side configurations
• Capability to provide a buffered reference through a user defined voltage divider
See the INA185 data sheet (SBOS378) for comprehensive information about the INA185 family of
devices.
3 Quick Start Setup and Use
The following instructions show how to set up and use the INA185 devices with the INA185EVM. For the
circuits in the following instructions, x = A to D.
Step 1. Connect an external dc supply voltage between 2.7-V and 5.5-V to the VCC test point TP2x,
and connect the ground reference of that supply to one of the GND test points: TP7x, TP8x,
or TP9x.
Step 2. The REF pin is connected to the GND pin in the default board. The voltage applied at the
reference input varies depending on how the device is going to be used. Further details
regarding the use of the reference voltage are discussed later in this document.
Step 3. Connect the input as described in Section 3.1.
3.1 Measurements
The INA185EVM can either simulate the voltage developed across a sense resistor based on a given set
of system conditions, or connect remotely to an existing shunt already included in a user application.
The following procedures are used to configure a measurement evaluation without a shunt. For the circuits
in the following instructions, x = A to D.
Step 1. Connect a differential voltage to the IN+ (TP6x) and IN– (TP3x) test points. With the
reference voltage set at ground, make sure that the IN+ pin is the more positive of the two
inputs.
Step 2. Measure the output voltage at the OUT test point (TP4x or TP5x).
NOTE: The output voltage is equal to the gain of the device multiplied by the differential voltage
measured directly at the device input pins.

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4 Circuitry
This section summarizes the INA185EVM components. For the following circuits, x = A to D.
4.1 C1x, J1x, R1x, and TP1x
C1x and R1x form a low-pass RC filter to the source that supplies the INA185 REF pin. By default, no
filter is installed, with R1x shorted by a 0-Ωresistor, and C1x not populated. J1x is a jumper that
conveniently allows the user to short the INA185 reference to ground, connect directly to an external
power supply, or short to a voltage set by a buffered voltage divider.
4.2 C2x and C3x, and TP2x
C2x is a 0.1-µF supply bypass capacitor for the INA185, U1x. The C2x footprint size, 0201, was chosen in
order to reduce overall layout size. A 0.1-µF capacitor is required for proper operation of the INA185, and
the user typically will not need to replace or adjust C2x. C3x is a footprint for an additional supply bypass
capacitor that the user can populate to further stabilize the supply. TP2x allows the user to connect an
external supply to the INA185 VS pin.
4.3 C4x
C4x is a 0.1-µF supply bypass capacitor for the optional INA185 reference pin buffer, U2x.
4.4 C5x, R2x, and R4x
C4x, R2x, and R4x form a differential mode filter to the input of the INA185, U1x. By default, this filter is
not installed, with R2x and R4x shorted by a 0-Ωresistor, and C4x not populated. If this filter is installed,
R2x and R4x must be less than 10 Ωwith low tolerance (≤1%) in order to minimize measurement error.
4.5 C6x, R3x, TP4x, and TP5x
C3x and R3x form a low-pass filter on the output of the INA185, U1x. By default, no filter is installed with
R3x shorted by a 0-Ωresistor, and C6x not populated. TP4x shows unfiltered output. By default, TP5x
also shows unfiltered output, but with R3 and C6 populated, TP5x shows filtered output.
4.6 C7x, R5x, and R6x
C7x and R5x form a low-pass filter to the input of the optional reference buffer. R5x and R6x form a
voltage divider that sets a desired reference voltage.
4.7 U1x
U1x is the INA185 current shunt monitor. Four gain-option segments are supplied within the INA185EVM
board. Each segment is populated with one of the available device gains. This configuration enables users
to test the devices and determine the best gain setting for a given application. For x = A to D, the gain is
20 V/V, 50 V/V, 100 V/V, and 200 V/V, respectively.
The following is a list of the factors involved in selecting the appropriate device:
• The differential input voltage is applied across the inputs, or developed based on the load current that
flows through the shunt resistor.
• The limiting factor that requires attention to be given to device selection is the output voltage.
• The selected device must allow the output voltage to remain within the acceptable range after the
developed input voltage is amplified by the respective device gain. The output voltage must remain
within the range of 10 mV greater than ground to 100 mV less than the supply voltage.
• An output less than the minimum allowable output requires a device with a higher gain. Likewise, an
output greater than the maximum allowable output requires a device with a lower gain.
4.8 U2x
U2x is a SOT-23 footprint for a buffer amplifier. By default, this part is not populated.

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5 Reference Voltage Setup
The INA185 allows for the use of an external reference. This reference determines how the output
responds to certain input conditions. The reference also enables these devices to be used in unidirectional
and bidirectional applications.
5.1 Unidirectional Mode
Unidirectional refers to a load current that flows in only one direction.
By default, each EVM board segment (one segment for each gain option) has the INA185 REF pin
connected to GND through a 0-Ωresistor and a jumper. This connection sets the INA185 for unidirectional
measurements. If bidirectional measurements are required, the EVM board segments can be modified to
add external voltages to the REF pins.
5.2 Bidirectional Mode
Bidirectional refers to a load current that flows in both directions.
The INA185 is able to measure bidirectional currents. The ability to measure current flowing in both
directions is enabled by applying a voltage to the REF pin. The voltage applied to REF sets the output
state that corresponds to the zero-input-level state. The output then responds by increasing to greater
than REF for positive differential signals (relative to the IN– pin), and by decreasing to less than REF for
negative differential signals. This reference voltage applied to the REF pin can be set anywhere from 0 V
to V+. For bidirectional applications, REF is typically set at midscale for an equal signal range in both
current directions. However, REF is set at a voltage other than midscale when the bidirectional current
and corresponding output signal do not have to be symmetrical.
5.3 REF Pin Configuration
Jumper connection J1x configures the respective EVM board segment for either unidirectional or
bidirectional operation. Shorting the left and middle pins of J1x sets the board for unidirectional
measurements. Removing the jumper and applying a voltage between 0 V to V+ to the middle pin of J1x
sets the board to a bidirectional measurement with the zero current output centered at the applied voltage.
Alternatively, install C4x, R5x, R6x, and U2x to provide a buffered voltage divider input from the supply to
set the reference voltage. For the buffered divider, install the jumper on the middle and right pins of J1x.

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6 Schematic, PCB Layout, and Bill of Materials
NOTE: Board layouts are not to scale. These figures are intended to show how the board is laid out.
The figures are not intended to be used for manufacturing INA185EVM PCBs.
6.1 Schematic
Figure 1 shows the schematic for the INA185EVM PCB. Only the schematic for the 20-V/V gain variant is
included because all other variants use the same exact circuit with the same layout. All components
associated with the 20-V/V INA185 A1 gain variant have the letter Aappended at the end. The 50-V/V A2
gain variant has Bappended, the 100-V/V A3 gain variant has Cappended, and the 200-V/V A4 gain
variant has a Dappended.
Figure 1. INA185EVM Schematic

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6.2 PCB Layout
Figure 2 through Figure 8 illustrate the PCB layout for the INA185EVM.
Figure 2. INA185EVM Top Overlay Figure 3. INA185EVM Bottom Overlay
Figure 4. INA185EVM Top Solder Mask Figure 5. INA185EVM Top Layer
Figure 6. INA185EVM Bottom Layer Figure 7. INA185EVM Bottom Solder Mask

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Figure 8. INA185EVM Drill Drawing

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6.3 Bill of Materials
Table 4 provides the parts list for the INA185EVM.
Table 4. Bill of Materials
DESIGNATOR QUANTITY VALUE DESCRIPTION PACKAGE REFERENCE PART NUMBER MANUFACTURER
!PCB 1 Printed-Circuit Board SENS037 Any
C1A, C1B, C1C, C1D 4 0.1uF CAP, CERM, 0.1 uF, 25 V, +/- 10%, X6S, 0201 0201 GRM033C81E104KE14D MuRata
H1A, H1B, H1C, H1D, H2A, H2B, H2C, H2D,
H3A, H3B, H3C, H3D, H4A, H4B, H4C, H4D 16 0 Bumpon, Hemisphere, 0.25 X 0.075, Clear 75x250 mil SJ5382000Z0EA 3M
J1A, J1B, J1C, J1D 4 SMT Header, 2.54mm, 3x1, Gold, SMT Header, 2.54mm, 3x1, SMT M20-8770342 Harwin
R1A, R1B, R1C, R1D, R2A, R2B, R2C, R2D,
R3A, R3B, R3C, R3D, R4A, R4B, R4C, R4D 16 0 RES, 0, 1%, 0.1 W, AEC-Q200 Grade 0, 0603 0603 RMCF0603ZT0R00 Stackpole Electronics Inc
SH-J1, SH-J2, SH-J3, SH-J4 4 Shunt, 100mil, Gold plated, Black Shunt 2 pos. 100 mil 881545-2 TE Connectivity
TP1A, TP1B, TP1C, TP1D, TP2A, TP2B,
TP2C, TP2D, TP3A, TP3B, TP3C, TP3D,
TP4A, TP4B, TP4C, TP4D, TP5A, TP5B,
TP5C, TP5D, TP6A, TP6B, TP6C, TP6D,
TP7A, TP7B, TP7C, TP7D, TP8A, TP8B,
TP8C, TP8D, TP9A, TP9B, TP9C, TP9D
36 Test Point, Miniature, SMT Testpoint_Keystone_Miniature 5015 Keystone
U1A 1 Bidirectional, Precision Low- and High-Side Voltage Output,
Current-Sense Amplifier, DRL0006A (SOT-5X3-6) DRL0006A INA185A1IDRLR Texas Instruments
U1B 1 Bidirectional, Precision Low- and High-Side Voltage Output,
Current-Sense Amplifier, DRL0006A (SOT-5X3-6) DRL0006A INA185A2IDRLR Texas Instruments
U1C 1 Bidirectional, Precision Low- and High-Side Voltage Output,
Current-Sense Amplifier, DRL0006A (SOT-5X3-6) DRL0006A INA185A3IDRLR Texas Instruments
U1D 1 Bidirectional, Precision Low- and High-Side Voltage Output,
Current-Sense Amplifier, DRL0006A (SOT-5X3-6) DRL0006A INA185A4IDRLR Texas Instruments
C2A, C2B, C2C, C2D, C5A, C5B, C5C, C5D,
C6A, C6B, C6C, C6D 0 1000pF CAP, CERM, 1000 pF, 100 V, +/- 10%, X7R, 0603 0603 C1608X7R2A102K080AA TDK
C3A, C3B, C3C, C3D 0 10uF CAP, CERM, 1000 pF, 100 V, +/- 10%, X7R, 0603 0603 GRT188R61E106ME13D MuRata
C4A, C4B, C4C, C4D, C7A, C7B, C7C, C7D 0 0.1uF CAP, CERM, 10 uF, 25 V, +/- 20%, X5R, 0603 0603 06035C104KAT2A AVX
R5A, R5B, R5C, R5D, R6A, R6B, R6C, R6D 0 10.0k CAP, CERM, 0.1 uF, 50 V, +/- 10%, X7R, 0603 0603 RC0603FR-0710KL Yageo
U2A, U2B, U2C, U2D 0 1-MHz, Low-Power Operational Amplifier for Cost-Sensitive
Systems, DBV0005A (SOT-23-5) DBV0005A TLV6001IDBVR Texas Instruments