Texas Instruments INA281EVM Manual de usuario

SBOU244–June 2020

INA281EVM

User's Guide

SBOU244–June 2020

INA281EVM

This user’s guide describes the characteristics, operation, and use of the INA281 evaluation module

(EVM). This EVM is designed to evaluate the performance of the INA281 voltage-output, current shunt

monitor in a variety of configurations. Throughout this document, the terms evaluation board, evaluation

module, and EVM are synonymous with the INA281EVM. This document also includes a schematic,

reference printed-circuit board (PCB) layouts, and a complete bill of materials (BOM).

Trademarks

All trademarks are the property of their respective owners.

WARNING

General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines

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1 General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines

Always follow TI’s setup and application instructions, including use of all interface components within their

recommended electrical rated voltage and power limits. Always use electrical safety precautions to help

ensure your personal safety and those working around you. Contact TI's Product Information Center

http://support/ti./com for further information.

Save all warnings and instructions for future reference.

WARNING

Failure to follow warnings and instructions may result in personal injury,

property damage or death due to electrical shock and burn hazards.

The term TI HV EVM refers to an electronic device typically provided as an open framed, unenclosed

printed circuit board assembly. It is intended strictly for use in development laboratory environments,

solely for qualified professional users having training, expertise and knowledge of electrical safety risks in

development and application of high voltage electrical circuits. Any other use and/or application are strictly

prohibited by Texas Instruments. If you are not suitable qualified, you should immediately stop from further

use of the HV EVM.

1. Work Area Safety

a. Keep work area clean and orderly.

b. Qualified observer(s) must be present anytime circuits are energized.

c. Effective barriers and signage must be present in the area where the TI HV EVM and its interface

electronics are energized, indicating operation of accessible high voltages may be present, for the

purpose of protecting inadvertent access.

d. All interface circuits, power supplies, evaluation modules, instruments, meters, scopes and other

related apparatus used in a development environment exceeding 50Vrms/75VDC must be

electrically located within a protected Emergency Power Off EPO protected power strip.

e. Use stable and nonconductive work surface.

f. Use adequately insulated clamps and wires to attach measurement probes and instruments. No

freehand testing whenever possible.

2. Electrical Safety

As a precautionary measure, it is always a good engineering practice to assume that the entire EVM

may have fully accessible and active high voltages.

a. De-energize the TI HV EVM and all its inputs, outputs and electrical loads before performing any

electrical or other diagnostic measurements. Revalidate that TI HV EVM power has been safely

de-energized.

b. With the EVM confirmed de-energized, proceed with required electrical circuit configurations,

wiring, measurement equipment connection, and other application needs, while still assuming the

EVM circuit and measuring instruments are electrically live.

c. After EVM readiness is complete, energize the EVM as intended.

WARNING

While the EVM is energized, never touch the EVM or its electrical

circuits, as they could be at high voltages capable of causing electrical

shock hazard.

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General Texas Instruments High Voltage Evaluation (TI HV EVM) User Safety Guidelines

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INA281EVM

3. Personal Safety

a. Wear personal protective equipment (for example, latex gloves or safety glasses with side shields)

or protect EVM in an adequate lucent plastic box with interlocks to protect from accidental touch.

Limitation for safe use:

EVMs are not to be used as all or part of a production unit.

Overview

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2 Overview

The INA281 device is a voltage-output, high-side and low-side measurement, current sense amplifier with

an enable pin in a very-small SOT-23 package. As shown in Table 1, the INA281 has gains that range

from 20 V/V to 500 V/V, depending on the gain option selected. The voltage developed across the device

inputs is amplified by the corresponding gain of the specific device, and is presented at the output pin. The

device accurately senses voltage drops across shunts at common-mode voltages from –4 V to +110 V,

independent of supply voltages. The device survives common-mode voltages from –20 V to +120 V. The

device operates with supply voltages between 2.7 V and 20 V, and draws a typical of 1.7 mA at room

temperature.

Table 1. INA281 Gain Option Summary

Product Gain (V/V)

INA281A1 and INA281B1 20

INA281A2 and INA281B2 50

INA281A3 and INA281B3 100

INA281A4 and INA281B4 200

INA281A5 and INA281B5 500

2.1 EVM Kit Contents

Table 2 summarizes the contents of the INA281EVM kit. Contact the Texas Instruments Product

Information Center nearest you if any component is missing. TI also recommends checking the INA281

device product folder at www.ti.com for any further information regarding this product.

Table 2. INA281EVM Kit Contents

Item Item Part Number Quantity

INA281EVM test board INA281EVM 1

2.2 Related Documentation From Texas Instruments

This document provides information regarding Texas Instruments' integrated circuits used in the assembly

of the INA281EVM.

Table 3. Related Documentation

Document Literature Number

INA281 product data sheet SBOSA29

INA281-Q1 product data sheet SBOSA01

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Hardware

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INA281EVM

3 Hardware

The INA281EVM provides basic functional evaluation of the INA281. The fixture layout is not intended to

be a model for the target circuit, nor is it laid out for electromagnetic compatibility (EMC) testing. The

INA281EVM consists of one PCB with an option to cut out ten individual PCBs, one for each of the five

gain options (1 to 5) and the two different pin outs (A and B) listed in Table 1. Be aware that because of

the different pinouts of the A and B versions, the layouts and test point locations are also different. Each of

the PCB cutouts consists of one INA281Xn device (where Xis A or B and nis 1, 2, 3, 4, or 5), and test

points and sockets for external hardware connections, as well as pads to solder down optional circuitry.

3.1 Features

The INA281EVM PCB provides the following features:

• Evaluation of all gain options through provided device boards

• Ease of access to device pins with test points

• Pads and sockets for optional filtering at the input pins and output pin

• Multiple input signal options, including a method to solder a shunt resistor (2512) and safely measure

current up to 5 A.

See the device data sheet for comprehensive information about the INA281 and the available gain

options.

Operation

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4 Operation

4.1 Quick Start Setup

Follow these procedures to set up and use one of the panels of the INA281EVM. For the following

instructions, X is pinout A or B, and n is gain option 1, 2, 3, 4, or 5.

Step 1. Choose the desired gain option panel and pin out variation.

Step 2. Connect an external dc supply voltage (between 1.7 V and 20 V) to a VS test point, and

connect the ground reference of that supply to a GND test point on the same panel.

Step 3. Provide a differential input voltage signal to the Vin+ and Vin– nodes by connecting the signal

leads to the J1_Xn pin 1 and J1_Xn pin 2 on the EVM, as explained in Section 4.2. The

INA281 is a unidirectional current-sensing device because there is no reference pin;

therefore, the device can only measure current in one direction.

4.2 Measurements

The INA281EVM allows the user to either emulate the voltage developed across a sense resistor based

on a given set of system conditions, or to connect the device inputs to an external shunt. Optionally, a

surface-mount technology (SMT) shunt resistor can be soldered across the Vin+ and Vin– pads, and these

inputs can be connected in series with the external system and load.

To configure a measurement evaluation without a the onboard shunt resistor, follow this procedure:

1. Connect a positive differential voltage across the Vin+ (J1_Xn) and Vin– (J1_Xn) tabs. Given the

internal GND reference of the device, make sure that the Vin+ pin is the more positive of the two

inputs.

2. Additionally, if the differential voltage supply is a floating supply, connect a –4-V to 110-V common-

mode voltage to the inputs by connecting the positive lead of the external voltage source to the

Vin– (J1_Xn) tab, and source ground to a GND test point. This action effectively raises the absolute

common-mode voltage of the input pins, while still retaining a positive input differential signal.

3. If an external shunt is being used make the connections such that the sensing location is across the

shunt and there will be no high current on the sensing path. See Getting Started with TI Precision

Labs - Current Sense Amplifiers: Shunt Resistor Layout

4. Measure the output voltage at the Vout test point with respect to GND.

To configure a measurement evaluation with a shunt resistor, follow this procedure:

1. Solder a 2512 resistor at the R1_Xn pads that connects the Vin+ (J1_Xn) and Vin– (J1_Xn) inputs.

2. Connect the Vin+ (J1_Xn) and Vin– (J1_Xn) tabs in series with the load and bus voltage sources

while powered off.

WARNING

If measuring current, first make sure that the equipment (shunt

resistor, wires, connectors, and so on) can support the

amperage and power dissipation. Secondly, make sure that the

current flowing through J1 does not exceed 5 A. Failure to do so

can result in hot surfaces (> 55°C), damage to the EVM, or

personal injury.

3. Power on the system and measure the output voltage at the Vout test point. Vout is equal to the

gain of the device multiplied by the differential voltage measured directly at the device input pins.

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EVM Components

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INA281EVM

5 EVM Components

This section summarizes the INA281EVM components. For the following instructions, X is pinout A or B,

and n is gain option 1, 2, 3, 4, or 5.

5.1 R2_Xn, R3_Xn, R4_Xn, C2_Xn, C3_Xn

R2_Xn, R3_Xn, R4_Xn, are factory-installed 0-Ω0603 resistors.

C2_Xn, C3_Xn, are not populated.

Collectively, these pads allow for user-defined filters for the input pins (IN+ and IN–) and output pin (OUT)

of INA281. If a filter is desired, remove these resistors and replace them with > 0-ΩSMT resistors, and

populate the capacitor pads with capacitors. When using input filtering, take into account the input bias

current of the device.

5.2 C1_Xn

C1_Xn is a 0.1-µF, power-supply bypass capacitor.

5.3 R1_Xn

R1_Xn is unpopulated, but allows for a surface-mount shunt resistor to be soldered down between the

Vin+ and Vin– pads, which are sensed by IN+ and IN– input pins. If used, make sure R1_Xn has proper

power dissipation for the selected current load. The chosen resistor must have a 2512 footprint.

5.4 U1_Xn (INA281)

U1_Xn is the location for the INA281Xn test device.

The following list of factors are involved in selecting the appropriate device gain:

• The differential input voltage is either applied across the inputs or developed based on the load current

that flows through the shunt resistor.

• Make sure that the output voltage does not exceed the supply voltage. This limiting factor requires

attention to device selection.

• 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 device-specified swing limitations for response in the linear range.

• An output below the minimum allowable output requires the selection of a device with a higher gain.

Likewise, an output above the maximum allowable output requires the selection of a device with a

lower gain.

Schematic, PCB Layout, and Bill of Materials

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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; they are not intended to be used for

manufacturing INA281EVM PCBs.

6.1 Schematics

Figure 1 shows the schematic of the INA281EVM for all gain versions for the A pinout. The difference is noted on the reference designator ending

in the gain option _An. Figure 2 shows the B1 gain panel and this is also a copy for all the other gain options with the reference designator ending

with the gain option _Bn.

Figure 1. INA281EVM Schematic: Gain A1 Panel

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Schematic, PCB Layout, and Bill of Materials

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INA281EVM

Figure 2. INA281EVM Schematic: Gain B1 Panel

Schematic, PCB Layout, and Bill of Materials

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6.2 PCB Layout

Figure 3 through Figure 9 illustrate the PCB layout for the INA281EVM.

Figure 3. INA281EVM Top Overlay Figure 4. INA281EVM Bottom Overlay

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