Texas Instruments bq77908AEVM User manual

User's Guide
SLUU854–February 2012
bq77908AEVM Evaluation Module
The bq77908AEVM-001 evaluation module (EVM) is a complete evaluation system for the bq77908A, a
4-series to 8-series cell Li-Ion battery protection integrated circuit. The EVM consists of a bq77908A circuit
module and a resistor cell simulator module, which can be used for simple evaluation of the bq77908A
functions. The circuit module includes one bq77908A integrated circuit (IC), sense resistor, power FETs
and all other onboard components necessary to protect the cells from overcharge, overdischarge, short
circuit, and overcurrent discharge in a 8-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 Windows®-based PC
software, the user can view the bq77908A registers and program the IC configuration and protection
limits.
Contents
1 Features ...................................................................................................................... 3
1.1 Kit Contents ......................................................................................................... 3
1.2 Required Equipment ............................................................................................... 3
2 bq77908A Circuit Module and Interfaces ................................................................................ 3
2.1 Circuit Module Connections ...................................................................................... 3
2.2 Signal Descriptions ................................................................................................ 4
3 bq77908AEVM Hardware Connection and Operation ................................................................. 5
3.1 Initial Considerations .............................................................................................. 5
3.2 Connecting the Cell Simulator .................................................................................... 6
3.3 Simulated Battery Connection .................................................................................... 6
3.4 Pack Connections .................................................................................................. 6
3.5 Basic Operation .................................................................................................... 7
3.6 Cell Connections ................................................................................................... 8
4 Software Installation ........................................................................................................ 8
4.1 System Requirements ............................................................................................. 8
4.2 Interface Adapter ................................................................................................... 8
4.3 Installing the bq77908GUI or bq77910GUI Evaluation Software .......................................... 10
5 Software Operation ........................................................................................................ 10
5.1 Menu Commands ................................................................................................. 12
5.2 Working With Register Values .................................................................................. 14
5.3 Status Section ..................................................................................................... 16
5.4 Basic Operation With Software ................................................................................. 17
5.5 Operation With Other Interfaces or Hosts ..................................................................... 17
6 Related Documents From Texas Instruments ......................................................................... 18
7 bq77908AEVM Circuit Description and Configuration ................................................................ 18
7.1 Battery Voltage Clamp ........................................................................................... 18
7.2 Device Power ..................................................................................................... 18
7.3 Cell Monitor Inputs and Configuration ......................................................................... 18
7.4 Ground Connection ............................................................................................... 20
7.5 Current Sense Connections ..................................................................................... 20
7.6 Filter Capacitors .................................................................................................. 20
7.7 FET Circuits ....................................................................................................... 21
7.8 Detection Sensing ................................................................................................ 21
7.9 Output Protection Components ................................................................................. 21
Windows, Microsoft are registered trademarks of Microsoft Corporation.
Aardvark is a trademark of Total Phase, Inc.
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7.10 Reserved Pins .................................................................................................... 22
7.11 Flag Outputs ...................................................................................................... 22
7.12 Thermal Sensor ................................................................................................... 22
7.13 ZEDE ............................................................................................................... 22
7.14 Programming Interface .......................................................................................... 22
8 bq77908A Circuit Module Physical Construction ...................................................................... 23
8.1 Main Board ........................................................................................................ 23
8.2 Resistor Cell Simulator .......................................................................................... 32
List of Figures
1 Basic EVM Setup ........................................................................................................... 7
2 Successfully Updated TI USB Interface Adapter ....................................................................... 9
3 EVM Connection for Communication and Programming............................................................. 11
4 GUI With Communication Established.................................................................................. 12
5 Communication Selection Window...................................................................................... 13
6 Commands Without Communication Established..................................................................... 13
7 Register Section ........................................................................................................... 14
8 Status Section.............................................................................................................. 16
9 Polling Status With Undervoltage Condition ........................................................................... 17
10 Top Silkscreen............................................................................................................. 23
11 Top Assembly.............................................................................................................. 24
12 Top Layer................................................................................................................... 24
13 Layer 2...................................................................................................................... 25
14 Layer 3...................................................................................................................... 25
15 Bottom Layer............................................................................................................... 26
16 Bottom Silkscreen ......................................................................................................... 26
17 Bottom Assembly.......................................................................................................... 27
18 Schematic Diagram, Sheet 1 of 2 ....................................................................................... 30
19 Schematic Diagram, Sheet 2 of 2 ....................................................................................... 31
20 Resistor Simulator Top Silkscreen ...................................................................................... 32
21 Resistor Simulator Top Layer............................................................................................ 33
22 Resistor Simulator Bottom Layer........................................................................................ 34
23 Resistor Simulator Top Assembly....................................................................................... 35
24 Resistor Simulator Bottom Assembly................................................................................... 36
25 Resistor Simulator Schematic Diagram ................................................................................ 38
List of Tables
1 Ordering Information........................................................................................................ 3
2 Cell Connections............................................................................................................ 4
3 PACK Connections ......................................................................................................... 4
4 Programming Interface Connections ..................................................................................... 4
5 Test Header Signals........................................................................................................ 5
6 Control and Status Connections .......................................................................................... 5
7 Adapter Cable Pinout ..................................................................................................... 10
8 Status Section Indicator Colors.......................................................................................... 16
9 Cell Count Component Configuration................................................................................... 19
10 bq77908A Circuit Module Bill of Materials ............................................................................. 27
11 Performance Specification Summary................................................................................... 32
12 Resistor Simulator Bill of Materials...................................................................................... 36
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1 Features
•Complete evaluation system for the bq77908A 4-series to 8-series cell Li-Ion or Li-Polymer battery
protector
•Populated circuit module for 8-cell, parallel FET configuration for quick setup
–Pads for components for configuration of additional cell counts and series FETs
•Power connections available on terminal blocks or banana jacks
•Control and status signals available on terminal blocks
•Resistor cell simulator for quick setup with only a power supply
•Personal computer software available for configuration
1.1 Kit Contents
•bq77908A circuit module
•Resistor cell simulator
•Set of support documentation
Table 1. Ordering Information
EVM Part Number Chemistry Configuration Capacity
bq77908AEVM-001 Li-Ion 8 cells Any
NOTE: Although capacity Table 1 is show as Any, practical limits of the physical construction of the
module typically limit the operation of the EVM to a 1P or 2P battery construction. See
Section 8 for board details.
1.2 Required Equipment
The following equipment is required to operate the bq77908AEVM in a simple demonstration.
•DC power supply, 0-V to 34-V at 0.5 A
•DC voltmeter or oscilloscope,
•DC power supply, ~3 V at .1 A or an approximately 15-kΩ, 1/4-W resistor
•Test leads to connect equipment
The following equipment is required to operate the bq77908AEVM with a more extensive demonstration.
•TI USB-TO-GPIO interface adapter
•Computer with USB port and compatible Windows 32-bit operating system
•Electronic load
•Additional power supplies
•TI bq77910GUI Evaluation Software (see Section 4).
2 bq77908A Circuit Module and Interfaces
The bq77908A circuit module contains the bq77908A IC and related circuitry to demonstrate the features
of the IC. A FET with heatsink is provided for the high-current discharge path. A lower current FET is
provided for the charge path. A thermistor provides temperature sensing for the device. Other components
provide support for the IC and connections to the board.
2.1 Circuit Module Connections
Connections are provided for the following interfaces:
•Direct cell connections
•PACK connections
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• Programming interface
2.2 Signal Descriptions
Signals available on the EVM are described in this section. For details on the location and connector
types, see Section 8. High current signals can be connected at either the terminal block or banana jack.
Refer to the physical construction section for identification.
Cell connections are described in Table 2. The default board assembly supports only 5 cells, so the upper
cell connections are not used. CELL0 and CELL5 are connected to the high current paths on the board
through 0-Ωresistors. This allows operation of the resistive cell simulator without external connections. If
the onboard resistors are removed, connections must be made off the board. See Section 8 for resistor
identification. Cell connection sequence is described in Section 3.6.
Table 2. Cell Connections
Reference Pin Number Signal Description
Designator
J13, J15 All BATT–Negative electrode of first (bottom) cell, high-current connection
Negative electrode of first (bottom) cell, optional separate monitor connection to
6 CELL0 cell
5 CELL1 Positive electrode of first (bottom) cell
4 CELL2 Positive electrode of second cell
J5 3 CELL3 Positive electrode of third cell
2 CELL4 Positive electrode of fourth cell
1 CELL5 Positive electrode of fifth cell,
5 CELL6 Positive electrode of sixth cell
4 CELL7 Positive electrode of seventh cell
J4 3 CELL8 Positive electrode of eighth cell, optional separate monitor connection to cell
2 NC9 Unused connection
1 NC10 Unused connection
J10, J11 All PACK+ Most positive cell output, high-current connection, shared with PACK+
Load connections are described in Table 3.
Table 3. PACK Connections
Reference Pin Number Signal Description
Designator
Positive output of evaluation board, shared with the battery high-current
J10, J11 All PACK+ connection
J12, J14 All DSG–Negative output of evaluation board for discharge
J16, J17 All CHG–Negative input to evaluation board for charge
Programming signals are described in Table 4. J3 signals are 3.3-V logic level.
Table 4. Programming Interface Connections
Reference Pin Number Signal Description
Designator
1, 2, 5, 7, 8 Not used
3 PGM Control signal for EEPROM programming voltage.
4 ZD Control signal for device ZEDE
J3 6 GND Signal reference for the IC
9 ECLK Serial interface clock connection
10 EDATA Serial interface data connection
1 14V Regulated 14-V input for IC programming
J2 2 GND Signal reference for the IC
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Test header or pattern signals are described in Table 5.
Table 5. Test Header Signals
Reference Usage Pin Number Signal Description
Designator
Default: shunt installed 1 Battery feed Power feed to 100-Ωshunt resistor
for normal operation.
J1 Remove shunt for U1 2 BAT Output of 100-Ωshunt resistor to IC BAT pin
supply current
measurement 1 VREG IC regulator output
IC zero delay test point and input pin, also connected
Default: no shunt. Install 2 ZEDE
J6 to J3
shunt to hold ZEDE high Pulldown resistor for strong pulldown of ZEDE if
3 PD required
Not populated. Alternate 1 TS IC temperature sense pin
J8 test point or remote 2 GND Signal reference for the IC
thermistor connection
Control and status signals are provided on terminal blocks. These signals are described in Table 6.
Table 6. Control and Status Connections
Reference Pin Number Signal Description
Designator
1 TS IC TS signal through a resistor
J7 2 GND Signal reference for the IC
Control signal for charger detection, connects through a resistor to the IC CHGST
1 CHGCTL pin
J9 2 DSGFLAG Diode and resistor isolated DSG signal
3 CHGFLAG Diode and resistor isolated CHG signal
3 bq77908AEVM Hardware Connection and Operation
This section describes the connection of the circuit module and EVM and simple operation in its default
configuration.
3.1 Initial Considerations
Boards are tested after assembly with a basic functional test. This test may not check every connection on
the board. Boards must be checked for function in the user’s environment before relying on the safety
features of the board. Operation of the board with test equipment before connecting cells is recommended
and described in this document.
The default configuration of the board is 8 cells with parallel FETs. Modifying the EVM for different cell
counts or FET configuration requires solder connections. It is recommended that the users familiarize
themselves with operation of the board in the default configuration before modifying the board, and check
the operation of the board with test equipment after any modification. Configuration of the board is
described in Section 7.
Be sure to observe the cautions and warnings in this document.
A variety of connections are provided on the EVM. The manufacturer's rating for the terminal blocks for
Pack and Battery connections is 32 A nominal. Parallel connections are provided for high-current
operation. The banana jacks are rated at 15 A. Safety agency ratings may be lower than the manufacturer
ratings; limit currents to appropriate values for your evaluation. Cell monitor terminal blocks and the
control signal terminal blocks are rated at lower currents and must not be used for high-current paths.
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A communication interface is not required for basic operation; it must be connected to the computer and
EVM circuit module only after proper installation of software. The software along with an appropriate
communication interface allows setting the programmable safety limits of the device and checking the
status after fault detection. Installation of the software and its use are described in Section 4 and
Section 5, respectively.
3.2 Connecting the Cell Simulator
The cell simulator consists of headers to mate the board and ten 200-Ωresistors to divide the battery
voltage between the inputs. Only 8 of these resistors are used for the bq77908A EVM. Power is provided
through the Cell0 and Cell8 connections on the terminal block headers. Various test points are provided
on the board. See Section 8 for additional details.
•Be certain no power is applied to the board.
•Unplug the screw terminal blocks from J4 and J5 of the EVM, and save these for later use.
•Plug the cell simulator board onto J4 and J5. Support may be required on the bottom of the EVM while
the connectors are pressed together firmly.
CAUTION
Do not connect or remove the cell simulator board while power is applied to the
EVM. The resistor pulldown or pullup from intermittent connections
over-stresses the device inputs.
3.3 Simulated Battery Connection
Connect a power supply between BATT–(negative) and PACK+ (positive). This power supply connects to
the resistor cell simulator through default connections on the bq77908A circuit module.
3.4 Pack Connections
A load or charger is connected to the pack terminals using the terminal blocks provided. It is
recommended that the load or charger be connected with the current switched off to prevent arcing or
transients during connection of the wires to the terminal blocks. Charger detection is required for the
bq77908A with a signal at the CHGST pin. Charger detection can be provided by connecting a resistor
from the CHGCTL terminal of the board to the PACK supply, or with a logic level voltage supply for
evaluation. An external resistor is required due to the low resistance pulldown on the board. The selected
resistor must keep the CHGST voltage above the VCHG_DET1 data sheet threshold over the entire
evaluation voltage range while limiting the power in the 1-kΩpulldown resistor to 1/16 W or less. A 15-kΩ,
1/4-W resistor is typically suitable for the default configuration; a smaller value may be required for low
voltage or if the configuration is changed.
WARNING
The CHGCTL must not be tied to the power supply without the
external resistor because the 1-kΩresistor on the board becomes
very hot and may damage the board.
Although designed for 30-A operation, the board may not dissipate enough power to operate without
exceeding all component ratings. The user must monitor the temperature of the board and components
during evaluation and provide cooling air and/or heatsinks as required for operation. The thermal sensor
on the board may not respond to protect the FETs from damaging temperatures due to its location and
possible thermal gradients on the board.
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“Charger”
supply
+
-
Resistor
Cell
Simulator
“Battery”
supply
+
-
~ 15k ohm
Load+
-
www.ti.com bq77908AEVM Hardware Connection and Operation
CAUTION
The bq77908A circuit module may be damaged by overtemperature. To avoid
damage, monitor the temperature during evaluation, and provide cooling as
needed for your system environment.
WARNING
The bq77908A circuit module may become hot during operation
due to dissipation of heat. Avoid contact with the board. Follow all
applicable safety procedures applicable to your laboratory.
CAUTION
Some power supplies can be damaged by application of external voltages. If
using more than one power supply, check your equipment requirements, and
use blocking diodes or other isolation techniques as needed to prevent damage
to your equipment.
The connection of the EVM looks similar to Figure 1.
Figure 1. Basic EVM Setup
3.5 Basic Operation
The following steps are suggested for basic operation of a default EVM with the cell simulator and the
default configuration in EEPROM.
1. Confirm that the cell simulator board is installed on the EVM.
2. Connect a power supply between the BATT–(negative) and PACK+ (positive) terminals.
3. Connect a 15-kΩ, 1/4-W resistor to the CHGCTL terminal of the board.
4. Set the bench supply to approximately 29 V.
5. Connect a disabled load between the DSG–(negative) and PACK+ (positive) terminals.
6. Wake up the part by momentarily connecting the 15-kΩresistor to the bench supply positive.
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7. Monitor the CHG and DSG test points using a meter or oscilloscope as desired.
8. Enable the load with a nominal 0.2-A or other current within the capability of the supply.
9. Increase the bench supply voltage to approximately 34 V, and observe that the CHG test point goes
low.
10. Reduce the voltage to approximately 29 V, and observe that the CHG test point returns high.
11. Decrease the voltage to approximately 20 V, and observe that the DSG test point goes low and the
load current drops. The device shuts down after 9 seconds at low voltage.
12. Remove the load, and connect the CHGCTL resistor to the supply to simulate a charger.
13. Increase the supply voltage to approximately 29 V, and observe that the DSG test point goes high,
and if the load is re-connected, that current flows again.
3.6 Cell Connections
For initial evaluation, it is suggested power supplies be used for cell simulation to observe the behavior of
the device. An isolated power supply with a resistor connected across its terminals may be connected to
test points on the resistor simulator to vary the voltage above or below the voltage of the other cells, or a
similar configuration may be used. The smaller the resistor value, the more current is required from the
battery simulator power supply and the smaller the influence on the voltages if cell balancing is operated.
Whether power supplies or cells are used, inductance in the high-current path must be minimized.
Inductance in this path can cause inductive transients at the board when the load current is stopped or the
bq77908A opens the discharge FET with current flow. Use heavy-gauge wires for the high-current
connections; minimize inductances by keeping leads close together.
When connecting cells to the EVM, the user must use care not to exceed the absolute maximum ratings of
the device. The bq77908A is designed with open-cell (wire) detection; however, fixturing must not pull
unconnected signals up or down. Signal reference (VSS) for the part is from the BATT–terminal of the
EVM, and this lowest potential must be connected first. Cells must be connected in sequence from lowest
to highest voltage as described in the data sheet. When terminating the cells to the removable terminal
blocks prior to connection to the EVM, the following steps are recommended:
1. Be sure the charger and any load is disconnected (CHGCTL is open).
2. Connect the cell stack negative high-current terminal to the EVM BATT–terminal.
3. Connect the lower cell group to the J5 connector.
4. Connect the upper cell group to the J4 connector.
5. Connect the cell stack positive high-current terminal to the EVM PACK+ terminal.
6. When removing cells, remove any charger and CHGCTL connection, then disconnect in the reverse
order.
4 Software Installation
This section describes how to install the software for the bq77908AEVM-001.
The BQ77908-10-GUI SW supports the bq77908A, and is described in this document as bq77908A
evaluation software.
4.1 System Requirements
The bq77908A evaluation software requires a 32-bit version of Windows XP, Windows Vista, or Windows
7. The computer must also have Microsoft®.NET framework version 2.0 or higher installed. Examples in
this document are from Windows XP.
4.2 Interface Adapter
The bq77908A evaluation software supports either the TI USB-TO-GPIO adapter (TI USB Interface
Adapter) or the Total Phase Aardvark™to provide communication with the EVM board from the computer.
The Total Phase Aardvark must be selected if desired. The EVM connector supports the TI USB Interface
Adapter; a special cable must be constructed if you wish to use the Aardvark.
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4.2.1 TI USB Interface Adapter
The TI USB Interface Adapter is the default option for the bq77908A evaluation software. Its pinout is
compatible with the bq77908AEVM board J3 connector.
The TI USB Interface Adapter http://focus.ti.com/docs/toolsw/folders/print/usb-to-gpio.html is actually a
separate EVM from Texas Instruments, and its default firmware is not compatible with the bq77908A. If
the firmware has already been updated to version 2.0.19 to work with other BMS-HCE products, additional
update is not required. If required, update the firmware using the following steps.
1. Obtain the USB-to-GPIO EVM Firmware Loader from
http://focus.ti.com/docs/toolsw/folders/print/usb2gpio-loader-sw.html, or search from power.ti.com
2. Download, extract, and run the installer
3. Installation requires the Microsoft .NET connection software. If a suitable version is not found on the
system by the installer, the user is prompted to obtain and install .NET.
4. Connect the TI USB Interface Adapter to the computer with the USB cable. The green LED illuminates.
5. Run the program, typically from Start →Run →Texas Instruments →USB-TO-GPIO Firmware
Loader.
6. Detailed instructions are provided in the Readme.txt file.
CAUTION
Do not disconnect the USB cable to the Interface Adapter during firmware
update. Loss of power may leave the adapter with corrupt firmware and be
unable to further update the firmware.
7. If you want to be able to return to the original configuration, back up the installed firmware before
update.
8. Load and update to the 2.0.19 version using the instructions provided.
9. If an error occurs, do not unplug the adapter. Re-try loading, load a different firmware, or re-start the
software and repeat until a load is successful.
10. After successful update, the window appears as is shown in Figure 2
11. After update, exit the program.
Figure 2. Successfully Updated TI USB Interface Adapter
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4.2.2 Aardvark Adapter
Although the Total Phase Aardvark adapter can physically mate to the EVM J3 connector, the pinout is
incompatible. A special interface cable must be constructed to use the Aardvark. Refer to the schematics
and Table 7 below for information.
CAUTION
Do not connect the Aardvark to the EVM without a properly constructed cable.
Damage may result to the EVM and/or Aardvark.
Table 7. Adapter Cable Pinout
USB-TO-GPIO (Mates to J3) Aardvark
IC Pin Name
or Description Pin Signal Pin Signal
VSS –signal 6 GND 2 GND
reference
SCLK 9 SCL 1 SCL
SDATA 10 SDA 3 SDA
ZEDE –
communication 4 GPIO4 5 MISO/GPIO
enable
Programming
voltage control 3 GPIO5 7 SCLK/GPIO
signal for
EEPROM
4.3 Installing the bq77908GUI or bq77910GUI Evaluation Software
Get the latest software version in the bq77908 and bq77910 GUI Evaluation Software tool
folder:http://www.ti.com/tool/bq77908-10-gui-sw, or search from power.ti.com. Check periodically for
software updates. Use the following steps to install the bq77908A Evaluation Software:
1. Copy the archive file to a directory of your choice; extract and run the bq77910 Setup.msi installer.
2. Follow the instructions, and make selections as required on the setup windows, selecting next as
required.
3. On the last window, select "close" to complete the bq77910 software installation.
5 Software Operation
This section describes connection of the communication interface to the EVM and operation of the
software.
Although the software will run without connection to a powered device, it is recommended to have the
device on when starting the software. Figure 3 shows connections for operation with the GUI software.
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