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Battery sensor

Three measurement-channels and CAN on-board

The MM9Z1J638 battery sensor by Freescale (US) comprises measurement-channels, a 16/32-bit MCU, and a CAN protocol controller in a single package. It is designed for both conventional and emerging battery chemistries.

The AEC-Q100 qualified sensor is suitable for 12-V lead acid and 14-V stacked Li-lon cells as well as 24-V truck batteries (Photo: Freescale)

THE BATTERY SENSOR ALREADY INTRODUCED IN 2012 is now available. It measures key battery parameters for monitoring state of health (SOH), state of charge (SOC) and state of function (SOF). A flexible four-cell front-end architecture supports different battery chemistries. Battery failure is one of the leading causes of vehicle breakdowns due to electrical system errors. Rising levels of electrical load in vehicles are placing increased strain on batteries as new, mission-critical requirements such as engine start-stop functionality become increasingly common. According to analyst firm Strategy Analytics, more than 52 million vehicles worldwide will support start-stop functionality by 2020. Start-stop requirements, together with others such as regenerative braking and intelligent alternator control, are driving demand for more precise sensing of the battery’s state to provide early failure warnings.

“Our introduction of the industry’s first single-package, automotive-qualified intelligent battery sensor with MCU and CAN components will help automakers cope with increasing algorithm complexity and data communication demands as cars become more connected and intelligent,” said James Bates from Freescale. “Also featuring integrated functional safety support, the new MM9Z1J638 battery sensor helps to support vehicle reliability even as automotive electrical system complexities increase.”

The integrated 16/32-bit S12Z micro-controller provides 128 KiB flash memory, 8 KiB RAM, and 4 KiB EEPROM. The analog front-end includes a two-channel, 16-bit sigma delta (ΣΔ) analog-to-digital converter (ADC) for simultaneous measurement of battery voltage and current, as well as a third 16-bit ΣΔ ADC for temperature monitoring using the integrated sensor and redundant measurement plausibility checks to support functional safety. The product’s input battery voltage measurement capability supports a wide range up to 52 V directly to the device as well as much higher voltage battery configurations when used with external voltage dividers. Its low operating duty-cycle enables operation in low-power mode for a majority of the time to help lower average system power consumption. Multiple wake-up triggers (current, temperature, etc.) can be used.

Reference designs with integrated hardware and software support for the battery sensor are available. Low-level drivers and BMS (battery management system) utility libraries are available to support custom battery modeling and shorten development cycles. There are offered several development kits including those for 4-cell Li-Ion battery applications.

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