Freescale Introduces First CAN-Based Intelligent Sensor for Automotive Battery Monitoring

The 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.

“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.”

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.

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 to allow a proper prediction of the battery’s SOH, SOC and SOF. 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.

MM9Z1J638 Xtrinsic battery sensor characteristics:
Battery voltage measurement Dedicated 16-bit second-order sigma-delta (ΣΔ) ADC with four dedicated voltage inputs covering different measurement ranges (10V, 16V, 28V, 52V)
Simultaneous sampling with current channel
Programmable signal filtering shared with current measurement
Four battery voltage measurement w/ internal divider
Five voltage sensor inputs routable to both voltage and temperature channels

Differential battery current measurement Dedicated 16-bit second order ΣΔ ADC with a programmable gain amplifier with four programmable gain factors
Gain control block for automatic gain adjustment
Measurement range up to +/-2000A with an accuracy of 5 mA and a resolution of 1 mA

Temperature measurement Internal on-chip temperature sensor
Dedicated 16-bit ADC with anti-aliasing filter
Accuracy: +/-2°C (-20 to 60°C) and +/-3°C (-40 to 125°C)
Five single ended sensor can be routed to Tsense ADC (PTBx) for ratio metric measurement (IC provides power supply and switchable ground allowing current saving when not used)
Ground switch to reduce power consumption when temperature measurement is off

Normal and low-power modes Current integration via 32-bit accumulator during low power mode
Programmable current threshold detection during low power mode
Programmable wake-up timer, triggered wake-up from LIN

Advanced system level management Internal oscillator with one percent accuracy
Built-in automatic ADC temperature compensation for optimum measurement accuracy over specified temperature range.
Communication via LIN 2.1, LIN 2.0 interface with fast mode for flash programming over LIN
An msCAN protocol controller with TxD and RxD terminals and bus wake-up detection
Enhanced 5V regulator capability to supply MCU, CAN PHY and other external components.
High-performance S12Z MCU with 32-bit ALU, 50 Mhz, 128 kByte flash, 8 kByte RAM, 4 kByte EEPROM all with ECC
Fast, die-to-die bus interface with transparent integration of analog IC registers into the MCU register map, automatic synchronization and error detection
Operating conditions
Ambient operating temperature: -40°C < Ta < 125°C
Junction operating temperature: -40°C < Tj < 150°C

Availability and pricing

The automotive-grade MM9Z1I638 and MM9Z1J638 devices are scheduled to be broadly available by the second half of 2013 from Freescale and authorized distributors worldwide for a suggested resale price of $4.25 and $4.41 (USD) in 10,000-unit quantities, respectively.