The LTC6804 is the third-generation multi-cell battery monitor introduced by Linear Technology in 2012. It enables accurate voltage measurement of up to 12 series-connected batteries almost simultaneously, offering improved accuracy compared to its predecessor, the LTC6803. This paper presents a battery management system (BMS) design that integrates the LTC6804 with a thermal resistance temperature sensor for multi-channel temperature monitoring. The system uses an STM32F103 microcontroller to manage a single BMS module, supporting the monitoring of 24 individual battery cells (using two LTC6804 devices) and the acquisition of 16 temperature channels, while also incorporating CAN bus communication.
The design is divided into two main parts: voltage and temperature acquisition, and control communication.
**1. Voltage and Temperature Acquisition**
The voltage and temperature acquisition section of the BMS includes two LTC6804 ICs, two LTC1380 multiplexer chips (each with eight channels), and one LTC6820 communication chip connected to the ECU. For the LTC6804-1 configuration, multiple devices are daisy-chained together, with one master device connected to the microcontroller. In contrast, the LTC6804-2 setup connects multiple devices in parallel to the microprocessor, with each device addressed individually. This paper focuses on the LTC6804-1 configuration. These devices communicate via the isoSPI protocol, which allows for reliable data transmission even in noisy environments.
To enhance system reliability, the LTC6804 modules are connected using isolation transformers and twisted-pair cables, providing excellent noise immunity. This setup ensures that the microcontroller can manage multiple LTC6804 nodes without interference. However, to prevent a single node failure from disabling the entire system, the microcontroller controls two nodes independently. Communication between the microcontroller and the BMS is handled through the internal CAN bus.
**1.1 Introduction to LTC6804**
The LTC6804 is a single-chip solution capable of measuring the voltage of 3 to 12 series-connected batteries. It requires at least three cells to provide a bias voltage of no less than 11V. Its stacked architecture supports hundreds of batteries, making it highly scalable. The chip features an integrated Zener voltage reference, third-order noise filtering, and an incremental accumulation ADC, enabling 16-bit resolution with an accuracy better than 0.04%. In fast mode, all cell voltages can be measured within 290 microseconds, along with passive charge balancing capabilities.
**1.2 Introduction to LTC6820**
The LTC6820 facilitates isolated SPI communication between two devices using a single twisted pair. It converts the standard four-wire SPI interface from the microcontroller to the isoSPI interface used by the LTC6804. This is achieved through an isolation transformer and twisted-pair connection, offering strong common-mode rejection and electrical isolation. The isoSPI bus inter-chain isolation is implemented using PULSE HX1188NL transformers, each containing two isolation transformers along with a center tap and a common-mode choke.
**1.3 Temperature Acquisition and LTC1380**
Temperature monitoring is achieved by combining an NTC thermistor bias circuit with the LTC1380 MUX (X8 MUX). The thermistor is connected in series with a high-precision resistor, and the voltage across the thermistor is measured after being divided by the reference power supply from the LTC6804. The MUX selects the appropriate channel, and the voltage is processed through a first-order proportional circuit before being converted into a temperature reading. This method ensures accurate and reliable temperature monitoring across multiple channels.
1.20MM Pitch Series
ZOOKE provides you with safe and reliable connector products, with 1.2 spacing products providing more possibilities for limited space and creating more value for the research and development and production of terminal products.
1.20 wire to board connectors,1.2 connectors,ZOOKE connectors
Zooke Connectors Co., Ltd. , https://www.zooke.com