SLVT251 July   2026

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 High-Voltage Stackable Architecture
      2. 2.2.2 Electrochemical Impedance Spectroscopy (EIS) Subsystem
      3. 2.2.3 EIS Synchronization Requirement
      4. 2.2.4 PWM Input as Crystal of the First BQ79826Z-Q1
      5. 2.2.5 Temperature Sensing and Multiplexer Network
      6. 2.2.6 Cell Balancing Circuit and Operation
      7. 2.2.7 MCU and System Control Architecture
      8. 2.2.8 Protection and On-Board Diagnostics
    3. 2.3 Highlighted Products
      1. 2.3.1 BQ79826Z-Q1
      2. 2.3.2 TMUX1308
      3. 2.3.3 TMP61
      4. 2.3.4 SN74LXC1T14
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Software
    3. 3.3 Test Setup
    4. 3.4 Pack Test Results
      1. 3.4.1 Cell Voltage Reliability Test
      2. 3.4.2 EIS Measurement Repeatability
      3. 3.4.3 Pack EIS Measurement Nyquist Plot
      4. 3.4.4 Current Consumption per BQ79826Z-Q1
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
      3. 4.1.3 PCB Layout Recommendations
    2. 4.2 Tools and Software
      1. 4.2.1 Tools
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5.     Trademarks
  11. 5About the Author

2 System Overview

The TIDA-010978 system is divided into several core functional blocks with clear interface and signal interaction:

High-Voltage Cell Monitoring Block

Dual BQ79826Z-Q1 devices are deployed in daisy-chain stacking to sample 52S cell voltages synchronously. Each BQ79826Z-Q1 performs local over/undervoltage judgment and transmits raw data to the main MCU for system-level processing. The daisy-chain topology simplifies high-voltage stacking wiring and improves synchronization accuracy.

Temperature Sensing and Multiplexer Block

TMUX1308 expands limited GPIO ports to achieve full temperature sampling matching cell quantity. TMP61 linear thermistors are placed on cell surfaces and busbar key positions. Each multiplexer reserves fixed resistance channels for online fault diagnosis of switch stuck or open circuit.

EIS Excitation and Control Block

Based on TMS320F28P55 and external FETs, the system generates high-resolution PWM signals to control the power stage. The active balancing circuit is reused as EIS excitation source to inject adjustable AC current into the battery pack. Voltage and current responses are sampled synchronously for impedance spectrum calculation. Multiple pack-level excitation modes are supported for different stacking configurations.

Communication Interface Block

On-board BQ79826Z-Q1s adopt capacitor-isolated daisy-chain; inter-board stacking uses transformer isolation to form ring communication network. Isolated CAN FD provides high-speed data interaction between BMU and upper BCU controller for cell data, EIS spectrum and fault upload.

Protection and Diagnosis Block

Integrates hardware threshold protection and software logic judgment, covering cell voltage abnormality, over-temperature, excitation overcurrent, wiring open circuit and communication failure. Fault code and timestamp are recorded and uploaded via CAN for remote maintenance.