Texas Instruments bq76940, bq76930, bq76920 User Manual
User's Guide
SLVU924B–March 2014–Revised April 2014
bq76920 Evaluation Module User's Guide
The bq76920EVM evaluation module (EVM) is a complete evaluation system for the bq76920, a 3-cell to
5-cell Li-Ion battery analog front end (AFE) integrated circuit. The EVM consists of a bq76920 circuit
module which is used for simple evaluation of the bq76920 functions. The circuit module includes one
bq76920 integrated circuit (IC), sense resistor, power FETs, and all other onboard components necessary
to protect the cells from overcharge, over discharge, short circuit, and overcurrent discharge in a 5-series
cell Li-Ion or Li-Polymer battery pack. The circuit module connects directly across the cells in a battery.
With a compatible interface board and Microsoft®Windows®based PC graphical user interface (GUI)
software, the user can view the bq76920 registers, adjust protection limits and enable FET control outputs.
Contents
1 Features....................................................................................................................... 2
1.1 Kit Contents.......................................................................................................... 2
1.2 Ordering Information ............................................................................................... 2
1.3 bq76920 Circuit Module Performance Specification Summary............................................... 3
1.4 Required Equipment................................................................................................ 3
2 bq76920 EVM Quick Start Guide.......................................................................................... 3
2.1 Before You Begin................................................................................................... 3
2.2 Quick Start........................................................................................................... 4
3 bq76940/bq76930/bq76920 Software .................................................................................... 5
3.1 System Requirements.............................................................................................. 5
3.2 Installing the bq76940/bq76930/bq76920 Software ........................................................... 5
3.3 Interface Adapter.................................................................................................... 5
3.4 Software Operation................................................................................................. 6
4 bq76920 Circuit Module Use.............................................................................................. 11
4.1 Cell Simulator...................................................................................................... 11
4.2 Evaluating with Simulated Current.............................................................................. 11
4.3 Reducing the Cell Count ......................................................................................... 12
4.4 Connecting Cells .................................................................................................. 13
4.5 Connecting to a Host ............................................................................................. 13
4.6 Gauge Circuits..................................................................................................... 13
4.7 Unused Components ............................................................................................. 13
5 bq76920EVM Circuit Module Physical Construction................................................................... 15
5.1 Board Layout....................................................................................................... 15
5.2 Bill of Materials .................................................................................................... 23
6 Related Documents From Texas Instruments.......................................................................... 29
1 EVM Connection for Basic Operation..................................................................................... 5
2 bq76940/bq76930/bq76920 Evaluation Software Display.............................................................. 6
3 Registers View ............................................................................................................... 8
4 I2C Pro View ................................................................................................................. 9
5 Sequence View............................................................................................................. 10
6 Simulating Current Setup.................................................................................................. 12
7 Top Silk Screen............................................................................................................. 15
8 Top Assembly............................................................................................................... 16
Microsoft, Windows are registered trademarks of Microsoft Corporation.
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List of Figures
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Features
9 Top Layer.................................................................................................................... 17
10 Layer 2....................................................................................................................... 18
11 Layer 3....................................................................................................................... 19
12 Bottom Layer................................................................................................................ 20
13 Bottom Silk Screen......................................................................................................... 21
14 Bottom Assembly........................................................................................................... 22
15 Schematic Diagram AFE .................................................................................................. 26
16 Schematic Diagram Gauge .............................................................................................. 27
17 Schematic Diagram Cell Simulator ...................................................................................... 28
1 Ordering Information ........................................................................................................ 2
2 Performance Specification Summary ..................................................................................... 3
3 Reducing cell count ........................................................................................................ 12
4 bq76920 Circuit Module Bill of Materials................................................................................ 23
1 Features
• Complete evaluation system for the bq76920 3-cell to 5-cell Li-Ion and Li-Polymer battery AFE
• Populated circuit module for 5-cell configuration for quick setup
• Power connections available on banana jacks
• Communication signals available on 4-pin connector
• Resistor cell simulator for quick setup with only a power supply
• PC software available for configuration
www.ti.com
List of Tables
1.1 Kit Contents
• bq76920 circuit module
• Cable to connect the EVM to an EV2400 or EV2300 interface board
1.2 Ordering Information
For complete ordering information, refer to the product folder at www.ti.com.
EVM Part Number Chemistry Configuration Capacity
bq76920EVM Li-Ion 5 cells Any
NOTE: Although capacity is shown as Any, practical limits of the physical construction of the module
typically limits the operation of the EVM to a 1P or 2P battery construction. Refer to the
physical construction section for board details.
Table 1. Ordering Information
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1.3 bq76920 Circuit Module Performance Specification Summary
This section summarizes the performance specifications of the bq76920 circuit module in its default 5-cell
parallel FET configuration.
Typical voltage depends on the number of cells configured. Typical current depends on the application.
Board cooling may be required for continuous operation at or below maximum current.
Table 2. Performance Specification Summary
Specification Min Typ Max Unit
Input voltage BATT+ with respect to BATT– 6 – 25 V
Continuous charge or discharge current 0 – 15 A
Operating temperature range 20 25 30 °C
1.4 Required Equipment
The following equipment is required to operate the bq76920 EVM in a simple demonstration:
• DC power supply, 0–25 V at 0.5 A
• DC voltmeter
• TI EV2300 or EV2400 interface board
• Computer with USB port and compatible Windows operating system and access to the internet
• TI bq76940/bq76930/bq76920 Evaluation Software (see Section 3)
• Test leads to connect equipment
• Electronic load or assorted resistors
Additional equipment may be desired to operate the bq76920 with a more extensive demonstration.
Features
2 bq76920 EVM Quick Start Guide
2.1 Before You Begin
The following warnings and cautions are noted for the safety of anyone using or working close to the
bq76920 EVM. Observe all safety precautions.
Warning The bq76920EVM circuit module may become hot during
Caution Do not leave the EVM powered when unattended.
The circuit module has signal traces, components, and component leads on the
bottom of the board. This may result in exposed voltages, hot surfaces or sharp
edges. Do not reach under the board during operation.
operation due to dissipation of heat. Avoid contact with the
board. Follow all applicable safety procedures applicable to
your laboratory.
CAUTION
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bq76920 EVM Quick Start Guide
The circuit module may be damaged by over temperature. To avoid damage,
monitor the temperature during evaluation and provide cooling, as needed, for
your system environment.
Some power supplies can be damaged by application of external voltages. If
using more than 1 power supply, check your equipment requirements and use
blocking diodes or other isolation techniques, as needed, to prevent damage to
your equipment.
The communication interface is not isolated on the EVM. Be sure no ground
potential exists between the computer and the EVM. Also be aware that the
computer is referenced to the Battery- potential of the EVM.
2.2 Quick Start
These steps describe quick connection of the bq76920 EVM to demonstrate operation of the AFE portion
of the EVM. For more detailed descriptions, refer to other sections of the user guide.
Refer to Figure 1 for the following steps.
1. Install the bq76940/bq76930/bq76920 evaluation software. Software is obtained from www.ti.com.
Install drivers for the EV2300, if necessary.
2. Remove shunts from headers connecting the AFE to the gauge.
3. If the EV2300 is used, install shunts on the SCL and SDA pull-up headers. Remove any pull-up shunts
when using the EV2400.
4. Close all dip switch positions (default is closed).
5. Attach the interface board communication adapter to the PC using USB cable. The EV2400 is
recommended, the EV2300 works if it is available and drivers are installed.
6. Attach the interface board I2C connector to the EVM I2C connector using the 4-pin cable.
7. Connect a 0-V DC power supply capable of 250 mA minimum to the “BATT” terminals and adjust to
approximately 18 V.
8. Press and release the BOOT switch.
9. Start the bq769X0 evaluation software. The GUI should display. Click on the Scan box to enable
repeated update of the display. The power supply may be adjusted within range of the part to observe
voltage changes in the GUI display Stack V/T/I section.
10. Set the voltage to approximately 18 V or a mid-range operating level. Clear any faults present by
clicking on the Clear Faults button of the All Read/Write Registers section of the GUI.
11. Click on the Continuous button in the GUI Coulomb Counter section. Enable the CHG_ON and
DSG_ON bits by clicking on the bit and commit the changes. Apply a load to the PACK terminals. Load
current must be within the capability of the supply and the components installed or 15 A, whichever is
lower. Observe the Coulomb Counter value change in the GUI display Stack V/T/I section.
12. Make other adjustments as desired, for evaluation.
Refer to other sections of this user guide for additional details.
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CAUTION
CAUTION
CAUTION
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DC Power Supply
+ -
Boot
switch
EV2300/
EV2400
I2C
SMB
Pull-ups
for
EV2300
Remove
for
EV2400
Remove gauge
shunts
Cell simulator
switches on for
power supply
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Figure 1. EVM Connection for Basic Operation
3 bq76940/bq76930/bq76920 Software
This section describes how to install and use the bq76940/bq76930/bq76920 software for the EVM.
The bq76940/bq76930/bq76920 software supports the bq76920 AFE I2C communication. This software is
intended to demonstrate register control and operation of the bq769x0 family of AFEs in the absence of a
gauge or MCU. This software is not intended to operate on a bus with another master. The AFE does not
turn on the protection FETs without control, the bq76940/bq76930/bq76920 software provides that control
from the GUI.
The software may also be identified as bq76940 or bq769X0 in menus or windows as space permits.
bq76940/bq76930/bq76920 Software
3.1 System Requirements
The bq76940/bq76930/bq76920 software requires a Windows 7, or later operating system. The computer
must also have Microsoft®.NET connection software version 4.0, or higher, installed. The examples in this
document are from Windows 7.
3.2 Installing the bq76940/bq76930/bq76920 Software
Find the latest software version in the software section of the EVM tool folder
http://www.ti.com/tool/bq76920EVM or search from power.ti.com. Check periodically for software updates.
Use the following steps to install the bq76940/bq76930/bq76920 software:
1. Copy the archive file to a directory of your choice, extract all files and run the setup.exe application.
2. Follow the instructions and make selections as required on the setup windows selecting Next, as
required. TI recommends installing the software in the default location.
3. On the last window, select Close to complete the bq76940/bq76930/bq76920 software installation.
3.3 Interface Adapter
The bq76940/bq76930/bq76920 evaluation software supports either the TI EV2300 or EV2400 interface
board to provide communication with the EVM board from the computer. Drivers must be installed for the
EV2300. The EV2400 uses operating system drivers and no separate installation is required. Do not
connect the EV2300 interface board to the computer until after the drivers are installed.
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If you have used an EV2300 with your computer previously, no additional installation is required. EV2300
drivers are included in the installation package and are found in the installation directory after installing the
software, typically at c:\Program Files (x86)\Texas Instruments\bq76940. Drivers are found at
http://e2e.ti.com/support/power_management/battery_management/m/videos__files/458983.aspx or
http://www.ti.com/tool/ev2300. Install the drivers by following these steps:
1. Navigate to the installation directory, typically C:\Program Files (x86)\Texas Instruments\bq76940
2. Run the file InstallEV2300Drivers.exe
The interface adapter should not be connected to the I2C connector if a gauge or MCU is connected to
the bus. Board pull-up shunts must be installed for the EV2300 and removed for the EV2400
3.4 Software Operation
This section describes connection of the communication interface to the EVM and operation of the
software.
Although the software runs without connection to a powered device, it is recommended to have the device
on when starting the software. Follow the directions in the quick start section. Figure 1 shows connections
for operation with the GUI software.
Start the software from the desktop shortcut bq769X0 Evaluation Software or the menu Start → All
Programs → Texas Instruments → bq769X0 Eval Software.
When started, the software looks for the communication interface and the device. If either is not found, a
popup window appears and must be acknowledged. When communication is established with the device,
the main window appears as shown in Figure 2.
The bq76940/bq76930/bq76920 software uses popup help tips on many of the control features.
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Figure 2. bq76940/bq76930/bq76920 Evaluation Software Display
The software window contains a menu bar and 3 sections. The top section is an I2C tool. The middle
section has 3 selectable views. The bottom section is a status section. Details are described in following
sections.
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3.4.1 Status Section
The bottom section displays the software name and version, the CRC mode and the communication
status. The CRC mode is automatically detected and the software communicates to the IC appropriately.
To the right of the CRC mode is a communication status area which may display information about the
communication with the device. Common displays and actions may include the following:
• Data channel name is invalid. Check the USB connection to the interface board. Exit and restart the
software
• No acknowledge from device. Check that the 4 pin cable is connected, the EVM is powered and boot
the device, then try to read the device.
• CRC read from device does not match calculated CRC. Check that the Read Device button was used
to detect the device. Check the connection of the 4 pin cable or its routing near high noise sources.
• Not able to find a free communication adapter. Check the connection of the USB cable to the
communication adapter.
• USB adapter timeout. Unplug and re-connect the USB cable and try to read from the device again.
• When the status area is blank, the last communication with the device was successful
3.4.2 I2C Section
The top section of the window below the menu bar has the I2C address and a byte communication tool.
The I2C address must be entered, the tool does not automatically detect the address. The default address
is 0x08 which is the default address for the device on the EVM. If the AFE on the EVM has been changed
to a different address, the address must be entered. The value is the 7 bit address and is shifted left 1 bit
position when observed on the bus.
The byte communication tool is useful to read or write a register. It is present with all views.
bq76940/bq76930/bq76920 Software
3.4.3 Menu Commands
The Help > About menu selection displays version information about the program. Other selections may
provide additional help or links to documentation.
The Options > Verify Writes selection allows selection of a readback of the registers once they are written.
The View menu allows selection of the center window display. Options are the Registers, I2C Pro or
Sequence views. Views can also be selected with buttons on the left side of the window.
Exit the program with the File menu.
3.4.4 Registers View
The registers view is the default display in the middle of the window when the software is started, see
Figure 3. It shows the control register values. If another view is displayed it is selected using the
Registers button on the left side of the window or from the menu.
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Figure 3. Registers View
The Read Device button at the top of the Registers view provides important setup of the
bq76940/bq76930/bq76920 software and the IC. The software reads the factory gain and offset data from
the device and populates these in the Stack V/T/I section for use in calculating display values. The
software writes the CC_CFG register to its proper value and also detects the CRC mode of the device and
sets the software appropriately.
The control registers are shown in the center of the display in the All Read/Write Registers section. Bits
are color coded as described in the section. Bits may be changed by clicking on the bit and selecting
Commit button in the Change value pop-up window. The default for the pop up window is to change the
polarity of the bit. Since clearing status bits requires a write of 1, the Set bit high needs to be checked in
the Change value pop-up window when clearing status register bits. A bit value change is displayed if the
Options menu Verify Writes is selected.
Control registers can also be changed as register values by writing in the value box to the right of the
value box. Scan must be disabled to enter values. Register values may also be changed using the I2C
byte write tool at the top of the window. Register changes are visible if the Verify Writes option is enabled.
The display may also be updated using the Update Display button or selecting Scan.
The All Read/Write Registers section contains 4 buttons to the right of the register display:
• Update Display: This button reads all control and value registers and updates the values, bit breakout
fields and control features.
• Clear Faults: This button clears the status register.
• Save Configuration: This button allows saving the displayed values of the control register to a file. A
pop-up box allows selection of the file name. The default file location is C:\Users\<accountname>\Documents\Texas Instruments\bq76940.
• Load configuration: This button allows loading the control register values from a file. A pop-up box
allows selection of the file, another pop up box lets you select whether to write the values to the
device. If faults are not set in the status register value in the file, they are not cleared by the write.
The Base Configuration section shown above the register detail provides convenient control of the
Coulomb Counter, ADC and Temperature Sensor selection as functional controls without locating the
control bits.
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The Data Scanning section allows periodic read of the device and display of the register values. The Scan
check box enables the read when checked. The update interval is displayed and can be changed with the
Change Interval button.
The Logging section has the Start Logging button. The values read from the device can be saved to a
file. Selecting the Start Logging button opens a bq76940 Logging popup window to enter the file name,
comments and to select the data groups to be logged. The file name must be entered with the pop up
window's Browse button. The scan interval can be changed, and the logging is actually started in the pop
up window. When logging is active, the registers user interface cannot be used and the button changes to
Stop Logging. Selecting the button stops the logging. Scan is not necessary before logging, it will start
with logging and cannot be disabled during logging.
The Stack V/T/I section is on the right side of the Registers view (Figure 3). The ADC Gain and Offset
boxes show the values that are used for converting the register data into values. These value boxes are
read only, they are updated by the values read from the device with the Read Device button. The Display
raw data read from device below check box allows display of the hex register values rather than converted
values. The V/T/I values are updated by the Read Device button, the Update Display button, or the Scan
option.
3.4.5 I2C Pro View
Figure 4 shows the I2C Pro view of the GUI. The I2C Pro view is useful to read or write several sequential
registers. If another view is displayed, it can be selected using the I2C PRO button on the left side of the
window or from the menu. The I2C Command box for each section specifies the starting register address
for the transaction.
bq76940/bq76930/bq76920 Software
3.4.6 Sequence View
Figure 5 illustrates the Sequence view of the GUI. This is useful to send timed sequences of register
reads or writes to the device. It can be selected using the SEQUENCE button on the left side of the
window or from the menu. A sequence is run by selecting its Execute button. The results of the sequence
are shown in the Sequence Dialog section. Edit the sequence by selecting the file name under the
sequence name in the window.
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Figure 4. I2C Pro View
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Figure 5. Sequence View
The installation comes with 3 sequence files. The Clear Faults files contain descriptions for requirements
for a sequence file. The Set UV Trip... file shows an example of a simpler format. Sequence files are
installed to: C:\Users\<account-name>\Documents\Texas Instruments\bq76940\sequence. Sequences are
loaded from this location when the program starts. Create new sequences with a text editor and save
them with the .bqseq extension. Up to 8 sequences can be stored, move other sequences to another
directory or change the extension. The sequences Sequence_Example.bqseq, Sequence Clear
Faults.bqseq, and UVTrip.bqseq are required, do not move them from the directory.
Typical uses of a sequence might include:
• Reading and clearing faults, then enabling CHG and DSG outputs
• Setting ship mode
• Setting a balance pattern
• Any repetitive multiple-register write used in evaluation
While sequences can be executed during logging, the logging is paused while the sequence executes.
Long sequences leave gaps in the log data.
3.4.7 Typical Operation of Software
Typical operation of the software involves the following steps, much like described in quick start section:
• Connect the EVM and related equipment
• Power the EVM
• Boot the EVM
• Start the software
• Read and change registers, as desired
If the board is powered off during the evaluation process:
• Power the EVM
• Boot the EVM
• Select the Read Device button
• Read and change registers, as desired
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If the interface board is connected to a system already in operation and the software has not been exited:
• Select the Read Device button
• Read and change registers, as desired
3.4.8 Operation with Other interfaces or Hosts
The bq76940/bq76930/bq76920 software does not support other interface boards or adapters other than
the EV2300 and EV2400. The software does not operate in a multi-master environment. If operated with
another host on the line, data collisions can occur. Also be aware that the EV2400 has internal pull-up
resistors to 3.3 V, connecting to some shared busses could damage devices on that bus if the bus voltage
differs.
4 bq76920 Circuit Module Use
The bq76920 circuit module contains the bq76920 IC and related circuitry to demonstrate the features of
the IC. Surface mount FETs are provided for the high current path. A thermistor provides temperature
sensing on the board. Other components provide support for the IC and connections to the board. Basic
operation is described in the quick start guide. For details of the circuit, refer to the physical construction
section.
4.1 Cell Simulator
The EVM includes a resistive cell simulator made up of 200-Ω series resistors. The top section of the S3
switch connects the BATT+ node to the top of the resistor string. The bottom of the resistor string is
connected to BATT-. The individual cell taps are connected to the cell monitor signals by other sections of
the dip switch. When operating with a power supply all switch sections should be closed. When operating
with cells, all the dip switch sections should be open to prevent loading the cells and discharging the
battery. The cell simulator resistors are located on the bottom of the board and may become warm during
operation. The orange LED near the dip switch indicates the cell simulator has power.
bq76920 Circuit Module Use
4.2 Evaluating with Simulated Current
The quick start guide describes connection for basic operation. Providing more than recognizable current
in that configuration can require a power supply with a significant power rating. Applying a charge current
can damage some power supplies. Figure 6 shows a method to force current through the control path
without a high wattage power supply or special equipment. The load power supply should be set at a low
voltage in a constant current mode. Polarity can be reversed on the load supply to simulate a charge
current. The battery simulation supply should never be reversed.
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