Texas Instruments INA226 User manual

User’s Guide
INA226EVM User’s Guide
ABSTRACT
This user’s guide describes the characteristics, operation, and use of the INA226 evaluation module (EVM).
This EVM is designed to evaluate the performance of the INA226. Throughout this document, the terms
evaluation board, evaluation module, and EVM are synonymous with the INA226EVM. This document includes a
schematic, reference printed circuit board (PCB) layouts, and a complete bill of materials (BOM).
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Table of Contents
1 Trademarks..............................................................................................................................................................................2
2 Overview..................................................................................................................................................................................3
2.1 Kit Contents........................................................................................................................................................................3
2.2 Related Documentation From Texas Instruments.............................................................................................................. 3
3 Hardware................................................................................................................................................................................. 3
3.1 Features............................................................................................................................................................................. 4
4 Operation.................................................................................................................................................................................4
4.1 Quick Start Setup............................................................................................................................................................... 4
4.2 EVM Operation...................................................................................................................................................................4
5 Circuitry................................................................................................................................................................................. 19
5.1 Current Sensing IC...........................................................................................................................................................19
5.2 Input Signal Path..............................................................................................................................................................19
5.3 Digital Circuitry................................................................................................................................................................. 19
6 Schematics, PCB Layout, and Bill of Materials................................................................................................................. 20
6.1 Schematics.......................................................................................................................................................................20
6.2 PCB Layout...................................................................................................................................................................... 22
6.3 Bill of Materials.................................................................................................................................................................23
1 Trademarks
All trademarks are the property of their respective owners.
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2 Overview
The INA226 is a current shunt and power monitor with an I2C or SMBUS-compatible interface. The device
monitors both a shunt voltage drop and bus supply voltage. Programmable calibration value, conversion times,
and averaging, combined with an internal multiplier, enable direct readouts of current in amperes and power in
watts.
The INA226 senses current on common-mode bus voltages that can vary from 0 V to 36 V, independent of the
supply voltage. The device operates from a single 2.7-V to 5.5-V supply, drawing a typical of 330 µA of supply
current. The device is specified over the operating temperature range between -40°C and 125°C and features up
to 16 programmable addresses on the I2C-compatible interface.
Table 2-1. Device Summary
PRODUCT
DIGITAL
PROTOCOL
ADC
RESOLUTION
MAX GAIN
ERROR
MAX OFFSET
VOLTAGE
INA226 I2C 16-bit 0.1% ±10 µV
2.1 Kit Contents
Table 2-2 lists the contents of the EVM kit. Contact your nearest Texas Instruments Product Information Center if
any component is missing.
Table 2-2. Kit Contents
ITEM QUANTITY
INA226EVM test board 1
Note that this EVM requires the TI Sensor Control Board (SCB), which is sold separately.
2.2 Related Documentation From Texas Instruments
This user's guide is available from the TI website under literature number SBOU276. 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 (800)
477-8924 or the Product Information Center at [phone]. When ordering, identify the document by both
title and literature number. Table 2-3 lists documentation related to the EVM. Click the links in Table 2-3 for
further information. The device name links to the product web folder on www.ti.com. The literature number links
to the document PDF.
Table 2-3. Related Documentation
DOCUMENT TITLE
DOCUMENT
LITERATURE
NUMBER
INA226 data sheet SBOS547
INA226-Q1 data sheet SBOS743
Getting Started with Digital Power Monitors SBOA511
3 Hardware
The EVM is an easy-to-use platform for evaluating the main features and performance of the INA226. The EVM
supports current measurements up to 10 amps through the PCB, and includes a graphical user interface (GUI)
used to read and write device registers as well as view and save results data.
The EVM is intended to provide basic functional evaluation of the devices. The layout is not intended to be a
model for the target circuit, nor is it laid out for electromagnetic compatibility (EMC) testing. The EVM consists of
two printed-circuit boards (PCBs). The larger PCB is referred to as the EVM, and has the INA226 installed. The
smaller PCB is referred to as the SCB Controller, and is used to interface the EVM with the GUI.
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3.1 Features
• GUI support to read and write device registers as well as view and save results data
• EVM detached from SCB for custom use cases
• Multiple EVM support with single SCB/GUI
• Conveniently powered from a common micro-USB connector through the SCB
4 Operation
4.1 Quick Start Setup
The following instructions describe how to set up and use the EVM.
1. Purchase an SCB if you do not already have one.
a. To use a PAMB Controller instead, see PAMB Compatibility.
2. Download this driver and install it as an administrator: https://www.ti.com/lit/zip/sbac253.
a. Follow the download prompts, a myTI account will be required.
b. Note that this driver is labeled as a PAMB driver, but is also used for the SCB.
3. Attach the EVM to the SCB Controller as shown in Figure 4-1.
a. Refer to Figure 4-2 when connecting multiple EVMs of the same type together.
4. Connect the EVM to the PC using the provided USB cable.
a. Insert the micro USB cable into the SCB Controller onboard USB receptacle J2.
b. Plug the other end of the USB cable into a PC.
5. Access the GUI from this link in either Chrome, Firefox, or Safari: https://dev.ti.com/gallery/info/
CurrentSensing/INA226EVM_GUI/.
6. Connect the GND reference of the external system to the GND node of the EVM (pin 1 of J1).
7. Provide a differential input voltage signal to the IN+ and IN– nodes by connecting the signal leads to J1 pin 5
or 6 and J1 pin 3 or 4 on the EVM as explained in Current Sensing Operation.
4.2 EVM Operation
To use the EVM with the SCB Controller (sold separately), connect the EVM as shown in Figure 4-1.
Figure 4-1. EVM (Left) Connected to SCB Controller (Right)
If using multiple EVMs, connect them as shown in Figure 4-2. Make sure to use a different I2C address for each
device. The GUI only supports up to 4 EVMs total.
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Figure 4-2. Multiple EVMs Connected to SCB Controller
4.2.1 Setup
4.2.1.1 Driver Installation
Download and install this driver: https://www.ti.com/lit/zip/sbac253. This is a one-time step per computer, and will
require a myTI account. Note that this driver is labeled as a PAMB driver, but is also used for the SCB. Unzip the
folder and run the .exe file with administrator privileges.
4.2.1.2 Firmware
Firmware updates will be pushed through the GUI if the previous driver was installed. Downloaded offline GUIs
will only update the SCB Controller with the latest firmware available at the time of download. To check for the
latest GUI or Firmware updates, launch the latest GUI version from the web browser.
4.2.1.2.1 Firmware Debug
If the firmware must be manually reinstalled for any reason, follow these steps to reinstall the firmware. Make
sure the EVM is connected to the SCB.
1. First, see if the GUI can program the firmware manually.
a. Plug in the SCB controller to the PC
b. Launch the GUI
c. It is possible that the MCU has already entered Device Firmware Update (DFU) mode. If so, the GUI
may notify you and try to update the firmware to the latest version.
d. If it does not update automatically, go to File > Program Device...
2. If step 1 is unsuccessful (or if the Program Device button is grayed out), manually configure the MCU on the
SCB Controller to be in DFU Mode. This can be done through either of the below methods with the SCB
Controller powered on:
a. Through software:
• Send the command 'bsl' on the SCB's USB Serial (COM) port.
b. Though hardware:
• For safety, turn off and disconnect all load sources and external voltages.
• While shorting the two test points labeled DFU (shown in Figure 4-3) with a pair of tweezers (or wire),
press and release the RESET button.
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Figure 4-3. Test Points Used to Enter DFU Mode Manually
• If the PAMB board is being used instead, these test points are located near PK1 and PK2.
With the MCU in DFU mode, the firmware can now be uploaded through the method outlined in Step 1.
4.2.1.3 GUI Setup and Connection
You can access the GUI from this link in either Chrome, Firefox, or Safari: https://dev.ti.com/gallery/info/
CurrentSensing/INA226EVM_GUI/.
4.2.1.3.1 Initial Setup
To set up the GUI the first time:
1. Make sure that the previously mentioned driver was installed successfully to ensure that everything works
properly and that the GUI can update the EVM firmware, if necessary.
2. Check to make sure the EVM/SCB Controller unit is plugged into the PC, then go to the previously-provided
GUI link.
3. Open the GUI Composer application to launch the GUI from the web browser (see Figure 4-4).
Figure 4-4. GUI Composer Application
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a. The GUI link will bring up all versions of the GUI. TI recommends to launch the newest version available.
b. For first-time GUI Composer setup, follow the prompts to download the TI Cloud Agent and browser
extension (see Figure 4-5). These prompts will appear after you close the README.md dialog box.
Figure 4-5. TI Cloud Agent
4. To download the GUI for offline use, click the icon in the GUI Composer application and follow the
prompts (see Figure 4-4).
4.2.1.3.2 GUI to EVM Connection
To connect the GUI to the EVM, follow these steps:
1. Setup and launch the GUI as described in Initial Setup.
2. Check to make sure that the EVM connected to the GUI, then close the README.md file page to initiate the
connection. If successful, the text Hardware Connected should be visible near the bottom left corner of the
GUI.
Figure 4-6. Hardware Connected
a. A green indicator with the device type and the text DEVICE CONNECTED should also be visible near
the top left of the GUI.
Figure 4-7. Device Connected
b. If the text Hardware Connected and DEVICE CONNECTED do not show in the GUI, long-press the
RESET button on the EVM to try again.
i. If that option does not work, check different hardware COM ports under Options > Serial Port.
Figure 4-8. Change Serial Port
c. If the hardware still does not connect, make sure you are using the correct GUI/EVM combination.
i. If you are using the correct GUI/EVM combination, you may need to reprogram the firmware of the
SCB, as described in Firmware Debug.
ii. Many connectivity issues can be addressed by doing one of the following:
1. Long-press the RESET button on the EVM with the EVM and SCB connected to each other.
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• Refreshing the GUI can also sometimes help this.
2. Connect the EVM to a different USB port.
• Avoid using long cables and USB hubs.
• If you are using a desktop PC, try a USB port on the back.
4.2.2 GUI Operation
Setup, launch, and connect the GUI to the EVM per GUI Setup and Connection. Refer to the sections below for
a description on how to use each page of the GUI.
4.2.2.1 Homepage Tab
The GUI starts out on the homepage tab. Click the (Home) icon on the menu to the left to return to the
homepage tab at any time.
From the homepage, you can easily confirm successful GUI to EVM connection (see GUI to EVM Connection),
as well as access helpful resources through the buttons on the bottom (see Figure 4-9).
Figure 4-9. Home Tab Links
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4.2.2.2 Configuration Tab
To do the initial setup for each connected EVM, click the (Configuration) icon on the menu to the left. Figure
4-10 shows an example of the configuration tool.
Figure 4-10. Configuration Tool
From this page you can set the number of EVMs you are using, and then for each EVM you can indicate the
physical hardware switch settings and configure your shunt and CURRENT_LSB. Below is a description of each
option and field on this page:
• Number of EVMs
– This setting is used to tell the GUI how many EVMs are connected to the SCB.
– Note, the SCB and GUI only support up to 4 INA226EVMs at a time.
– Changing this here also changes the same setting in the Results Data tab.
• Selected EVM
– This setting indicates which EVM you are currently changing settings for.
– This also selects the EVM that is connected to the Registers tab.
• Hardware Switch Settings
– Set these settings to match the physical switch settings on the EVM.
– Note, this setting needs to be set before changing any other settings on this page. The GUI will block the
other settings until this is set.
– Changing this here also changes the same setting in the Results Data tab.
• Shunt/Current Configuration
– This section is used to input shunt information as well as to help calculate the CURRENT_LSB and set the
CALIBRATION register. Here is a description of how to use each field:
• RSHUNT
– Input the value of the used shunt resister in mΩ.
• Max Expected Current
– Input the value of the maximum expected current across the shunt resistor in Amps.
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– If the Max Expected Current field is left blank, then CALIBRATION can be adjusted manually, and
the tool will tell you the True Max Current that can be measured with the EVM.
• CURRENT_LSB
– This is the calculated CURRENT_LSB value in Amps. This field gets populated automatically from
the Max Expected Current field.
– This field can be changed manually if desired, and changes will filter downward.
• CALIBRATION
– Calculated value for CALIBRATION based off of RSHUNT and CURRENT_LSB. When this field
changes, the value is automatically written to the CALIBRATION register.
– This field can be changed manually if desired, and changes will filter downward.
– Changing this value from the register map page also changes it here.
• True CURRENT_LSB
– This is the actual CURRENT_LSB value in Amps back calculated from the CALIBRATION register
with the given shunt resistor value.
– This is the value used for calculations in the Results Data section.
• True Max Current
– This is the maximum measurable current in Amps based off of the VSHUNT and CURRENT
registers, using RSHUNT and the True CURRENT_LSB for calculations.
• Required Sensing Range
– This shows the required sensing range to measure the Max Expected Current with the specified
shunt resistor.
– If a Max Expected Current is not specified, then the True Max Current field will be used instead.
4.2.2.3 Registers Tab
To view and edit the device registers, click the (Registers) icon on the menu to the left. The Registers tab will
look like the one shown in Figure 4-11.
Figure 4-11. GUI Registers Tab
From this page, you can read and write device registers on the EVM. Here are some important notes:
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• Use the Selected EVM drop-down menu at the top to choose which device to work with on the register map.
– Note, changing this here also changes the same setting for the Configuration tab.
– Functionally, this setting sets the default read/write address in the MCU and then reads all register values
back to update the register map. Note that if data is being collected at a high frequency, then this may
cause a minor delay in the data collection. For optimal performance, set device settings before you start
collecting data.
• By default, all changes are automatically written to the device. If desired, you can change the Immediate
Write setting to Deferred Write to only allow writing when you are ready.
– You can modify writable register values from any of these methods:
• Through the widget settings in the Field View section on the right.
• Changing the Value directly with either hex or decimal values.
• Double-clicking on any individual bit.
• Turning on Auto Read will only update registers in the register map, and not the plots in the Results Data
section.
– Leaving Auto Read on while collecting data for plots can interfere with data collection timing.
• For questions about a register or register bit field, select the icon.
– For even more questions about registers, check the data sheet.
• For convenience, register settings can be saved and loaded back later to any device with the same register
map. To do this, go to File > Register Data, as shown in Figure 4-12.
Figure 4-12. Save and Load Register Settings
– TI recommends to press the Read All Registers button after loading data to update the register map with
the actual device values.
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4.2.2.4 Results Data Tab
To view and collect results data over time, click the (Results Data) icon on the menu to the left. Figure
4-13 shows part of the results data page for reference, which may look different depending on the number of
connected EVMs.
Figure 4-13. Results Page and Settings
Below is a description of how to use the buttons and settings at the top of the Results Data tab and next to each
plot:
• Results to collect/show
– Use this section to select which register values to collect data for. If a results register is unselected before
the COLLECT DATA button is pressed, then the plot below will be hidden and the EVM will not try to read
this register during the collect cycle (even if the conversion is enabled).
– If you disable one of these settings while the EVM is collecting data, then the plot will not show, but data
will still be collected and the plot will update in the background. Simply reselect to show data.
• Number of EVMs
– Set the Number of EVMs drop-down menu to the number of EVMs currently in use.
• See Figure 4-2 for how to attach multiple EVMs together.
• Changing this here also changes the same setting in the Configuration tab.
– The GUI only supports up to 4 INA226EVMs at a time.
– Switch settings
• Use the onboard switches to select a different address for each EVM.
• Set the switch settings in the GUI to match the setting for each connected EVM.
–EVM 1 will automatically populate with the lowest addressed device unless a setting has already
been selected.
– Changing this here also changes the same setting in the Configuration tab.
• If more than one device is being used, a * symbol will appear next to the selected EVM that is being
used on the register map and configuration tabs.
– Changing the switch settings of any EVM sets that EVM as the selected EVM.
• Collect/Plots settings
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– Collect Data
• Press the COLLECT DATA button to start data collection.
• In this mode, the MCU reads and sends the selected result values for each device over a USB BULK
channel. All results from one device are read before moving on to the next device.
– All result values from all EVMs together are considered one "sample set".
• Although you can read and write to other registers through the register map page while collecting data,
it is possible that this adds a delay to the data being collected.
• Press the STOP COLLECT button to stop collecting data.
– #Samples Only
• If this checkbox is selected, then the GUI will automatically stop collecting data after the number of
samples specified in the #Samples box have been collected.
• If not selected, the GUI will continue collecting data and only store the most recent #Samples.
– Delay between samples
• Sets the delay between the start of each sample set.
• Desired delay time may not be obtainable if it is set faster than the read loop, which depends on the
number of results being collected, the number of EVMs, and your CPU.
• Although you can read and write to other registers through the register map page while collecting data,
it is possible that this adds a delay to the data being collected.
– Auto Delay
• Sets delay based on conversion times, averaging, and number of channels being converted.
• If multiple EVMs are being used, the time put in the delay box will be from the EVM with the shortest
calculated delay value.
– Save All Plots
• Press the SAVE ALL PLOTS button to save the data for each currently selected result from the Results
to collect/show section in a spreadsheet.
• Press the SAVE PLOT button next to each plot to save just the data from that plot in a spreadsheet.
– Clear All Plots
• Press the CLEAR ALL PLOTS button to clear the data from all plots together.
• Press the CLEAR PLOT button next to each plot to clear the data from just that plot.
– #Samples
• Change the number in this box to change the number of samples shown in each plot.
– Changing this number clears out the plot buffers, so the plots will be cleared on the next read.
– Y-Axis Options
• Manual Scale
– Checking this box will set all EVM results in this plot to the same scale value specified by the Max
and Min fields.
– When this is not selected, each EVM will have it's own Y-axis scale based on the min and max
value for that EVM's result values.
• Max
– The maximum Y-axis value to use for all EVMs in this plot.
– If this field is empty when Manual Scale is selected, then it will auto populate with the maximum
value currently in the plot.
• Min
– The minimum Y-axis value to use for all EVMs in this plot.
– If this field is empty when Manual Scale is selected, then it will auto populate with the minimum
value currently in the plot.
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4.2.3 Current Sensing Operation
The EVM can be used with either an onboard or external shunt resistor. To use the onboard shunt resister,
solder a 2512 surface-mount technology (SMT) shunt resistor across the pads of R1, and connect it in series
with the external system and load current through J1. An external shunt can be connected directly across
the terminals of J1. There are two terminals each for IN+ (J1 pins 5 and 6) and IN– (J1 pins 3 and 4) for
convenience.
4.2.3.1 Detailed Setup
To configure a measurement evaluation, follow these steps:
1. Connect a shunt resister by doing either of the following:
a. Solder a 2512 resistor across the pads of R1 that connects the IN+ and IN– inputs.
b. Connect an external shunt across the IN+ and IN– terminals of J1, preferably across pins 4 and 5, as
shown in Figure 4-14 and Figure 4-15.
i. 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 the TI Precision Labs - Current
Sense Amplifiers: Shunt Resistor Layout video for more information.
2. Connect the IN+ and IN– terminals in series with the load while powered off.
a. When measuring more than 10 A, make sure the high current path does not go through the EVM
(including the terminal block J1), as shown in Figure 4-14.
Load Current Line IN+ Load Current Line IN-
Figure 4-14. IN+ and IN– Wiring for More Than 10A
b. When using 10 A or less with either an onboard or external shunt, the current path can be passed
through the EVM. Figure 4-15 shows a convenient way to use the multiple IN+ and IN- terminals with an
external shunt for this use case.
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Load Current Line IN+ Load Current Line IN-
Figure 4-15. IN+ and IN– Wiring for 10A or Less
WARNING
When 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 10 A. Failure to do so can result in
damage to the EVM, or personal injury.
The EVM may get hot.
3. Connect the VBUS terminal (J1 pin 2) to the desired bus voltage (likely either IN+ or IN–).
a. If VBUS and dependent features are not being used, this channel can be used as an ADC input for
another voltage.
4. Connect the system ground to the GND terminal (J1 pin 1).
5. Power on the system, and observe the device states and outputs through the GUI.
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4.2.4 Direct EVM USB Communication
If desired, the EVM can be communicated with directly without the use of the GUI through the USB port. This is
done by sending the desired command string over the serial COM port and receiving the results either through
the COM port or the USB BULK channel, based on the mode. This is useful for interfacing the EVM with custom
setups, scripts, or GUIs.
4.2.4.1 Standard USB Read and Write Operations
Use the serial COM port to read and write registers through USB commands using the following format:
• Set device address format: setdevice DEVID
– Where setdevice is always lower case, and DEVID is defined as:
• The 4 LSBs of the address in decimal format. Ex, for an address of 0x4A, use 10.
– Note, when the SCB is reset while one or more EVMs are connected, the address will default to the lowest
address found.
• The SCB checks for I2C or SPI at start up, if no device is attached, it will default to SPI. Reset the SCB
with an I2C EVM connected to use I2C.
– For example, to set the INA226 with a register address of 0x4A you could send the command: setdevice
10
– For this example, the EVM would return the acknowledgment and state ("idle" or "collecting") in JSON
format:
{"acknowledge":"setdevice 10"}
{"evm_state":"idle"}
• Read register format: rreg ADR
– Where ADR is the address in hex, and rreg is always lower case.
– Register addresses can be in upper or lower case, and do not need to be led by '0x'. 0 padding register
addresses is also optional. For example, to read register address 0xFF, some valid commands include:
• rreg ff
• rreg 00ff
• rreg 0xFF
– When '0x' is used, the 'x' must be lower case.
– For this example, the EVM would return the results and state ("idle" or "collecting") in JSON format:
{"acknowledge":"rreg 0xFF"}
{"register":{"address":255,"value":8800}}
{"evm_state":"idle"}
• Write register format: wreg ADR VAL
– Where ADR and VAL are in hex, and wreg is always lower case.
– Register addresses and values can be in upper or lower case, and do not need to be led by '0x'. 0 padding
register addresses and values is also optional. For example, to write register address 0x1 with the value
0x436f, some valid commands include:
• wreg 0 436f
• wreg 00 0x436f
• wreg 0x00 0x436F
– When '0x' is used, the 'x' must be lower case.
– For this example, the EVM would return the results and state ("idle" or "collecting") in JSON format:
{"acknowledge":"wreg 0x00 0x436f"}
{"console":"Writing 0x436f to CONFIGURATION register"}
{"evm_state":"idle"}
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4.2.4.2 Collect Data Through the USB BULK Channel
The Collect Data function reads the desired result registers and sends the data based on the specified settings.
This function works best with continuous conversion mode and does not configure the EVM or associated
register settings for you. Collect mode started and stopped via the serial COM port, however the results will be
sent over the USB BULK channel. To use this mode, use the following format:
• Start collecting data format: collect timerPeriod collectFlags channelAddressIDs numDevices
– Where collect is always lower case, and each parameter is the decimal representation of the value in the
following format:
• timerPeriod
– The timer delay used in the MCU to allow data collection sample sets (in µs, unsigned 32bit value).
• collectFlags
– a byte of data that has a 1 to collect and a 0 to not collect each register value type, according to
the following definitions (note to only use energy and charge flags when the device supports that,
otherwise set to 0):
• VSHUNT = 0b1000
• VBUS = 0b0100
• CURRENT = 0b0010
• POWER = 0b0001
• channelAddressIDs
– This is the 4 LSBs of each I2C address chained together, starting with the LSBs.
• For example, if EVM 1 is at address 0x41 and EVM 2 is on ox43, the value here would be
0b00110001
• NumDevices
– The number of EVMs chained together (1-4).
– For example, to start data collection for VSHUNT and VBUS every 2.2 ms, for two INA226EVMs with EVM
1 address = 0x41 and EVM 2 address = 0x43, you would send: collect 2200 12 49 2
• For this example, the EVM would return the acknowledgment and state in JSON format:
{"acknowledge":"collect 2200 12 49 2"}
{"evm_state":"collecting"}
– The USB BULK channel receives data in the format: frameID deviceNumID address registerSize data
• Where each parameter is the decimal representation of the value in the following format:
– frameID (1 byte)
• Always reads 0. Used to ensure data is aligned.
– deviceNumID (1 byte)
• An ID number corresponding to the EVM number.
– From the above example, this will be 1 if reading from EVM 1 which had address set to 0x41,
and 2 if reading from EVM 2 which had a address set to 0x43.
– address (1 byte)
• The register address that was read from the device.
– registerSize (1 byte)
• The number of bytes that the following data will have.
– data (1 byte at a time)
• The register data value, given in bytes with the most significant byte first.
• Stop collecting data format: stop
– Where stop is always lower case.
– The EVM will return the acknowledgment and state in JSON format:
{"acknowledge":"stop"}
{"evm_state":"idle"}
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4.2.5 PAMB Compatibility
If desired, this EVM and GUI can be used with the PAMB Controller (DC081A) by jumper wiring the pin headers
of the PAMB to the EVM. Figure 4-16 shows which pins on the PAMB correspond to the EVM header pins.
Note not to add too much resistance in the jumper wire connection setup or the signal may degrade and cause
communication errors.
Figure 4-16. EVM to PAMB Connection
Operation www.ti.com
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5 Circuitry
This section summarizes the EVM subsystems and their components.
5.1 Current Sensing IC
This section describes the INA226 and supporting components.
U1 is the INA226 current-sensing device. C1 and C2 are bypass capacitors that are placed near the sensor to
help mitigate power supply noise and provide current quickly to the device when needed. LED D1 with current
limiting resistor R4 are used to indicate when the EVM is powered on.
The device pins can be monitored directly through the test points TP1 – TP12. Note that there are two extra test
points on GND for convenience.
5.2 Input Signal Path
This section describes the circuitry of the input signal path.
J1 is the main connection terminal. Pin 1 of J1 is used to tie the system ground to the EVM ground. Pin 2 of J1
is used for the VBUS measurement within the sensor. Pins 3 and 4 are tied to IN–, and Pins 5 and 6 are tied to
IN+. There are two pins each for IN– and IN+ for convenience.
R1 can be used for an optional onboard shunt resistor with a 2512 footprint. Alternatively, a shunt can be placed
across the IN+ and IN– terminals of J1. If desired, a differential voltage can be applied directly for measurement
tests.
C3, R2, and R3 combine to make an optional input filter. R2 and R3 are populated with 0-Ω resistors by default.
When using input filtering, take into account the input bias current of the device. C3 can also be used without R2
and R3 to reduce noise. See the data sheet for more info on input filtering.
5.3 Digital Circuitry
This section describes the digital circuitry around the device.
J2 and J3 are the main header pins that connect the digital and power pins to the SCB Controller or other EVMs.
J3 connects to the EVM/SCB on the right, while J2 connects to more EVMs on the left. R5 and R6 are used as
pullup resistors for the main digital IO pins.
SW0 and SW1 set the I2C address of the device. This can be useful when using the EVM with a custom
controller (other than the SCB Controller), or when connecting multiple EVMs together. Currently the SCB
Controller and GUI are set up to use four EVMs at a time.
R8 is used as a pullup resistor for the ALERT pin, which is routed to both J2 and J3. LED D2 and current
limiting resistor R7 are used to indicate when the ALERT has triggered. Header J4 and jumper SH-J4 are used
to disconnect the ALERT pin from the EVM ALERT bus by disconnecting from J3. This is primarily used when
working with multiple EVMs, so that the individual ALERT LEDs can be seen on each EVM when the ALERT bus
is not needed.
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6 Schematics, 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 EVM PCBs.
6.1 Schematics
Figure 6-1 and Figure 6-2 show the schematic of the INA226EVM. Figure 6-1 shows the circuitry for the EVM.
Figure 6-2 shows the mechanical components included with the EVM.
GND
0
R2
0
R3
0.1uF
C3
GND
GND
1
2
3
4
5
6
J1
TP8
SDA
TP9
SCL
TP11
A1
TP10
A0
TP12
ALERT
PD2_B
TP5
GND
TP6
GND
TP2
IN-
TP4
IN+
TP1
VBUS
TP3
VS
0.1uF
C2
D2
10k
R7
+3V3
+3V3
1µF
C1
4.7k
R8
D1
10k
R4
1.0k
R5
1.0k
R6
+3V3
+3V3
PN5
PN4
PN5
PN4
GND+3V3
GND
PN5
PN4
GND+3V3
GND
MNT_1
7
MNT_2
8
MNT_3
9
MNT_4
10
1
2
3
5
6
4
SW0
CUS-14TB
MNT_1
7
MNT_2
8
MNT_3
9
MNT_4
10
1
2
3
5
6
4
SW1
CUS-14TB
0.01
R1
+5V
+3V3
1
3
56
4
2
7
910
8
12 11
J2
1
3
5
7
9
11
J3A
2
4
6
8
10
12
J3B
GND
+5V
+3V3
GND
PN4
PN5
PD2_A
PP1
PP0
PQ3
PQ2
PQ0
PQ1
PN5
PN4
TP7
GND
A1 1
A0 2
ALERT 3
SDA 4
SCL 5
VS+
6GND 7
VBUS
8
VIN-
9
VIN+
10
INA226AIDGSR
U1
SH-J4
PD2_B
PD2_A
PD2_B
1
2
J4
Figure 6-1. Schematic Circuitry
Schematics, PCB Layout, and Bill of Materials www.ti.com
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