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Theory of Operation
2 Theory of Operation
The BQ79631-Q1 is designed to verify the safe operation of charging, discharging, and power transfer to a load
in an EV/HEV system. Various voltage sense measurements are made at critical nodes within the BJB/BDU to
make sure that the vehicle is operating as intended at all times. In a typical BMS system, a BQ79631-Q1 is used
to gather critical data in the following areas:
•
HV ±
•
Link ±
•
Charge ±
•
HV_Fuse
•
HV_Extra1_Plus/HV_Extra2_Plus
The typical BMS system with stacked modules has three main sub-systems, as shown in
•
Host controller - in this case a TMS570 LaunchPad
•
A BQ79631-Q1 configured as an isolated communication bridge device - a BQ79600EVM , BQ79616EVM, or
a BQ79631EVM can also support this .
•
BQ79616EVM based modules attached to cells - these can be stacked up to 35 total devices (including the
bridge device).
All commands and data are communicated with a host through either a UART or daisy-chain communication
connection. The BQ79631 remains idle until a command is received from the host. The BQ79631 can support
a host PC or microcontroller (through the UART connection header) or a daisy-chain interface from a BQ79600
implemented as a communication bridge.
The typical flow is for the host to go through the following simplified sequence:
1. Wakeup the BQ79631EVM board by sending a WAKEUP pulse when using the UART interface, or send a
WAKE tone when using the BQ79631EVM in a stack with other BQ79616EVM boards for a large battery
pack. (Typically an auto address signal is needed if using the BQ79631EVM in a stack of other BQ devices
but is not needed if using a single BQ79631EVM).
2. Send a sample command to the BQ79631-Q1 to read the voltage measurement results.
3. If no stop command is sent, then the BQ79631-Q1 has a built-in timeout (set by the user), after which time
the discharge is stopped automatically.
6
BQ79631EVM Evaluation Module
Figure 2-1. Typical BMS System with Stacked Modules
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™
.
www.ti.com
Figure
2-1:
SLUUCC3 – FEBRUARY 2021
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