Atmel intros AVR Microcontrollers for automotive motor control applications
(Product News, 14 Apr 2008 )
Atmel Corporation has announced the availability of a new family of AVR 8-bit microcontrollers dedicated to motor control applications for automotive. The ATmega16M1 and ATmega32M1 are the first devices developed for the control of sensor and sensorless brushless DC (BLDC) motors for automotive applications.
With an increasing number of motors inside a car, automotive manufacturers need smaller and lighter motors with higher torque than brush motors. They are now moving to BLDC motors that require more sophisticated electronic devices to precisely control speed and torque. This brings new challenges; among them is high temperature – 150 degrees Celsius – for some applications under the hood.
The ATmega16M1 and ATmega32M1 have been developed to serve that need and provide an integrated solution for advanced motor control applications with CAN and LIN connectivity. Thanks to the collaboration with Vector, the leading manufacturer of software tools and software components for automotive networking, a complete hardware and software networking solution is available.
Window lift motor with anti-pinch brings a good example of the requirement. Breaking assistance, steering wheel assistance, ventilation, cooling, sliding doors are other examples. Finally, a new category on its own is the admission control and turbo charger control for which the motor and possibly its controller is exposed to elevated temperature over the standard 125 degrees Celsius (typically 150 degrees).
Based on the high performance AVR 8-bit RISC architecture, the ATmega16M1 and ATmega32M1, integrate all of the basic peripherals necessary to satisfy the needs of complex algorithms. Integrating analog blocks like 10-bit ADC, with differential amplifiers and programmable gain options, Analog comparators with selectable comparison levels, interrupt on pin change I/Os. The microcontrollers provide all necessary resources to control BLDC motors in their system environments.
The ATmega16M1 and ATmega32M1 include independent positive and negative comparator inputs to allow sensorless motor control with no external active components. Three individual comparators are available for back Electro Magnetic Field (EMF) measurements. An additional comparator is available for over-current detection. Its reference (comparison level) can be fixed via the DAC output or any external reference voltage. Clocked up to 64-MHz, the 12-bit versatile synchronous Power Stage Controller generates 6 complementary programmable high speed and precision signals to control a motor’s 3 half bridges. The maximum frequency is 64 kHz, with a resulting voltage resolution of about 1/1000. Hardware fault detection will automatically and immediately put the motor in a safe position in case a failure is detected.
About 2 Kbytes of Flash (20 bytes of SRAM) is necessary for the low level drivers for the PSC. Typical code size for BLDC sensor drive is about 2.7 Kbytes of Flash (about 350 bytes of SRAM). BLDC sensorless drive is about 3 Kbyte of Flash and 300 bytes of SRAM. With integrated hardware routines, the code size for LIN is reduced to about 1 Kbyte of Flash. The code size of a CAN stack is about 16 Kbytes to 24 Kbytes Flash. For applications that may require more code, a 64 Kbytes version will be introduced later in 2008.
ATmega16M1 and ATmega32M1 offer a unique feature combination to safely and securely run any brushless DC motor via the appropriate driver and power elements. Effective Power stage controller and integrated analog functions generate a limited number of interrupts, reducing the code size and improving the real-time behavior of the applications.
