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Freescale introduces intelligent sensor for automotive lead-acid battery monitoring; addressing increasing electrical loads and stop-start

Freescale Semiconductor introduced the MM912J637 intelligent battery sensor (IBS), which accurately measures the voltage, current and temperature of lead-acid batteries and calculates the battery state, all while operating in harsh automotive conditions. The ability to accurately assess these battery parameters is becoming more important with increases in the number of hybrid vehicles on the road and overall electronic content in vehicles, as well as the introduction of stop-start systems.

The MM912J637 IBS enables precision measurement of key battery parameters in automotive and industrial applications. The device integrates a S12 microcontroller and a SMARTMOS analog control integrated circuit in a single-package solution, enabling significant reduction of effective application board space, Freescale says.

The MM912J637 IBS is designed to meet the highest automotive standards for electrostatic discharge, electromagnetic compatibility and zero defect quality levels. It is fully AEC-Q100 automotive qualified for operation from -40°C to +125°C, providing low power consumption in the target application. It comes in a small form factor, 7 x 7mm QFN package with wettable flanks technology, enabling optical inspection during assembly.

In today’s vehicles, the increasing electrical load presents a challenge to the battery. Vehicle breakdowns caused by the electrical system can usually be traced back to the lead-acid battery and can generally be avoided by knowing the precise state of the battery, Freescale notes. The battery must be able to provide enough energy to crank the engine and be available as a passive power source to support new functions of hybrid vehicles such as stop-start and intelligent alternator control. In addition, the power consumption of the IBS needs to be as low as possible to ensure energy efficiency.

Freescale’s fully integrated, battery monitoring device communicates using a local interconnect network (LIN). It includes a two-channel, 16-bit analog-to-digital converter (ADC) for simultaneous measurement of battery voltage and current and an independent 16-bit ADC for temperature measurement. The IBS provides accurate monitoring with high resolution, even in worst-case conditions to allow a proper prediction of the battery’s state-of-health, state-of-charge and state-of-function. The automotive certified, in-vehicle LIN network communicates these parameters periodically or on-request.

The MM912J637 supports precise current measurement via an external shunt resistor at the negative pole of the battery and precise battery voltage measurement via a series resistor at the positive pole. The integrated temperature sensor combined with battery mounting allows accurate battery temperature measurement.

Freescale’s MM912J637 intelligent car battery sensor is available now in sample quantities, with production quantities planned for September 2011. Evaluation kits and software tools are available now.


Henry Gibson

With the new sealing techniques, automobile batteries should be single cell units, and there should be a special starting battery from EFFPOWER or Atraverda. The round cells can be placed anywhere with multiple strings for more energy and lower weight. Freescale ought to develop a Germanium Shottky diode of high current to prevent cell reversal. ..HG..


I don't get the interest in Lead Acid when the world is heading to Li-ion.
I think Germanium Schottky is a processed that never happened.
Freescale doesn't do power devices - only chips.
Look to Int'l Rectifier, Fairchild, OnSemi, STMicro and several others for power devices. They know what process works.
Cell-reversal is best avoided using cell management electronics (passive or active balancing circuits).
Power diodes are expensive and waste too much energy for use in power electronics.

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