Battery Monitoring Gains More Precision

Electric vehicles battery monitoring is improving, gaining more precision with the newest sensor released by Freescale Semiconductor, the MM9Z1J638 Xtrinsic battery sensor.

This is the industry’s first CAN-based battery sensor that accurately measures the voltage, current and temperature of lead-acid and lithium-ion batteries, as well as calculating the battery state – all while operating in harsh automotive conditions.

Accurate knowledge of these battery parameters has become critical due to the increase in hybrid vehicles and overall electronic content, as well as the introduction of start-stop systems in automobiles.

Freescale’s MM9Z1J638 Xtrinsic battery sensor offers a robust and cost-effective solution for designers, enabling precision measurement of key battery parameters in automotive and industrial applications. The device integrates an S12Z microcontroller (MCU) and a SMARTMOS analog control integrated circuit in a single-package solution, providing low power consumption in automotive and industrial environments.

The MM9Z1J638 Xtrinsic battery sensor is fully AEC-Q100 automotive qualified for operation from -40°C to +125°C and comes in a small form factor, 7 x 7mm QFN package.

In today’s vehicles, the rising number of electrical loads presents a challenge to the battery. It must be able to provide enough energy to crank the engine, as well as act as a passive power source to support new functions such as start-stop and intelligent alternator control. Precise knowledge of the battery’s state of health (SOH), state of charge (SOC) and state of function (SOF) can provide early detection of impending failure, the leading cause of vehicle breakdowns due to the electrical system. In addition, the power consumption of the battery sensor itself must be as low as possible to ensure energy efficiency.

“Devices such as the intelligent battery sensor are becoming necessary as electronic content and start-stop systems in automobiles continue to increase in quantity and importance,” said Gavin Woods, vice president and general manager of Freescale’s Analog & Mixed-Signal Products Division. “We are providing the industry’s first CAN-based, automotive-qualified and cost-effective solution that enables precise monitoring of critical battery parameters.”

Freescale’s fully integrated battery monitoring device 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 battery sensor provides accurate monitoring with high resolution even in worst-case conditions.

The battery sensor can communicate these parameters at intervals or on request from the in-vehicle network via either the LIN or CAN protocols (CAN requires an external PHY).

The MM9Z1J638 supports precise current measurement via an external shunt resistor at the negative terminal of the battery and precise battery voltage measurement via a series resistor at the positive terminal.

The integrated temperature sensor combined with battery mounting allows accurate battery temperature measurement. Eternal temperature sensor inputs allow accurate cell temperature measurement.

The automotive-grade MM9Z1I638 and MM9Z1J638 devices are scheduled to be broadly available by the second half of 2013.