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Multichannel Data Acquisition Saves System Costs by Combining High Functionality with a Novel Daisy-Chain Interface in Li-Ion Battery Monitoring Applications

The AD7280 Li-Ion battery monitoring IC contains all the functions required for fast accurate monitoring and safe control of stacked Li-Ion batteries as used in hybrid electric vehicles. Comprehensive functionality, voltage, temperature measurements, fault alarm output, and cell balancing capability are coupled with best-in-class specifications.

The device saves system costs by allowing devices to be stacked in large voltage environments (over 1000 V for 3.5 V Li-Ion+) without the use of multiple isolators. No interface components are necessary as data flows up and down the daisy chain. For optimum state of charge and maximum efficiency, it is important to monitor temperature, as well as every Li-Ion cell voltage in a stack. Each device can measure six voltages and six temperatures, drive six cell balance transistors, and has alarm functionality. Each cell balancing output is biased with respect to the cell being equalized, further reducing external biasing components. The alarm functionality includes over- and undervoltage as well as over- and undertemperature. The part is available in both 48-lead LQFP and 48-lead LFCSP packages.

When managing battery cells, accuracy, speed, and power relate directly to energy transfer efficiency and longevity. The low power mode (≤4 µA in power-down), high speed, 1 MSPS ADC, and accuracy of ±0.1% total unadjusted error (TUE) allow tight management capabilities to increase the number of charge/discharge cycles and increase the discharge period.


AD7280 Features

  • 12-bit ADC, 1 µs per channel conversion time
  • 6 analog input channels: CM range 0.5 V to 27.5 V
  • 6 temperature measurements inputs
  • Daisy-chain and cell balancing interface
  • Reference: 3 ppm
  • Low quiescent current
  • One SPI interface for up to 300 channels
  • On-chip registers for channel sequencing
  • VDD operating range: 7.5 V to 30 V
  • Temperature range: –40°C to +105°C

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