Battery management system keeps electric engines safe

-January 12, 2018

Automotive industry pundits are claiming that 25% of all automobiles sold will have electric engines by the year 2025. I do not yet have an electric vehicle, but when I do get one, I want it to be safe, as well as efficient and reliable.

Maxim Integrated’s latest battery management system (BMS) technology, including their newest MAX17843, not only meets ISO26262 certification but is the industry’s only single-chip solution to achieve ASIL D compliance. I like that.

[Read about ASIL D here: Auto SoCs: Race to ASIL D]

Automotive OEMs can enhance the safety of their lithium-ion battery packs with robust communications, comprehensive diagnostics, and lower system costs with the new device, which is a 12-channel, high-voltage smart sensor data-acquisition IC.

So, what is ‘robust communication’?

In order to have robust communication in an automobile, the BMS system needs to make fast and accurate voltage measurements. The Maxim BMS IC does this because, together with high EMC performance, there is an innovative daisy-chain design and a fast SAR A to D converter. Designers have the choice of selecting different architecture types for their automotive system designs. The isolated controller area network (CAN) architecture, based on a star configuration, is robust. A break in the communications wire would disrupt only one IC, while the rest of the battery pack remains safe. The caveat here is that the CAN architecture has a high bill of materials (BOM) cost, requires a microprocessor and CAN for each IC, and has relatively slow communication speeds.

Maxim uses another option, a proprietary daisy-chain architecture, that is recognized for delivering reliable communication at a faster rate than an isolated CAN architecture. It is also lower in cost for the design architecture. Their reliable, distributive, and cell management controller (CMC) architecture with differential universal asynchronous receiver/transmitter (UART) uses capacitive isolation that reduces failure in time (FIT) rates. This UART, a high flexibility bus structure supports 100m daisy-chain segments and enables robust communications in noisy environments. I like standardization, but unique initiatives in design architecture trump that in order to get a better design in the end product.

Evaluation kit

The MAX17843EVKIT# evaluation kit demonstrates the capabilities of the MAX17843 IC. Vertical headers on the kit allow for the connection of multiple EV kits, supporting up to a 32-device (max) daisy-chain configuration. Just like many EV architectures with a multitude of batteries.

Key features

  • Battery-cell string emulation
  • UART interface
  • Windows XP-, Windows Vista-, Windows 7-, and Windows 10-compatible software

The evaluation kit is available for $1,000.

Environmental and packaging

It operates over the −40ºC to +125ºC temperature range and is available in a 64-pin LQFP package (10×10mm).

Pricing

The MAX17843 is available on Maxim's website for $7.61 (1000-up, FOB USA).

Steve Taranovich is a senior technical editor at EDN with 45 years of experience in the electronics industry.


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