Dynamic data integrity affects automotive infotainment applications
By Duncan Bennett, Ramtron International
The quantity of dynamic data in today’s infotainment applications is exploding. This data is often essential for the correct operation of a system and/or is user-centric, changing as the user’s environment changes (e.g. local traffic information). Advanced infotainment systems, therefore, require a nonvolatile storage memory that guarantees high data availability and maintains data integrity.
By Duncan Bennett, Ramtron International
The quantity of dynamic data in today’s infotainment applications is exploding. This data is often essential for the correct operation of a system and/or is user-centric, changing as the user’s environment changes (e.g. local traffic information). Advanced infotainment systems, therefore, require a nonvolatile storage memory that guarantees high data availability and maintains data integrity.
Sudden Power Loss
A common problem that many automotive infotainment systems designers face is sudden power loss. This typically occurs any time the engine is restarted after a stall. Power loss can cause data corruption and, therefore, disrupt proper system operation, unless provisions are designed-in to maintain data integrity.
The following standard circuit makes the most of nonvolatile F-RAM (ferroelectric random access memory) to prevent the pitfalls of sudden power loss in automotive applications. F-RAM memory efficiently replaces a typical EEPPROM + capacitor combination; F-RAM uses much less power than EEPROM and writes much more quickly, eliminating the need for a capacitor to keep the power alive while writing is completed in a power-loss scenario. In addition, the F-RAM-based solution requires less physical board space than the EEPROM and capacitor combination, while the cost of eliminating the capacitor can prove a significant difference in applications that demand a large amount of capacitance.
The EEPROM and F-RAM circuits below are essentially equivalent:
F-RAM is commonly used when the system demands that data be stored upon power loss. F-RAM has already been adopted in advanced navigation systems to maintain system integrity if the power suddenly fails. In systems that rely on a DVD for mapping information, F-RAM is used to record the position of the DVD reading head, so if power is unexpectedly lost (i.e. the vehicle engine stalls) the DVD player can quickly resume from its last position. The solution is to continuously write the position of the head to the F-RAM, making use of F-RAM’s virtually unlimited endurance.F-RAM also solves the problem of navigation systems losing contact with enough satellites to make a firm position fix. This typically occurs when the vehicle enters a tunnel or an underground garage. If the position of the vehicle is being constantly stored in the F-RAM, the navigation system can use the F-RAM-stored position until a new satellite position fix is acquired. This also means that the position is available if power is suddenly lost. This type of continuous writing is a common technique when using high-endurance F-RAM.
High endurance/low power
Many of today’s new automotive radio formats handle large quantities of data in addition to the regular audio channels. This data ranges from traffic or weather information to road conditions and should be available as soon as the driver starts the car. This means that the radio must download the data while the car engine is off. Since the system cannot know when the driver will return to the vehicle, it must download and store the data continuously.
While automobile manufacturers are demanding more sophisticated car radio systems, they are increasingly limiting the amount of power that can be drawn from the vehicle’s electrical supply, particularly when the engine is off. This presents car infotainment designers with a very difficult challenge. F-RAM solves this because it can be written to as often as required, with no practical limitation on the memory’s endurance. This means that data is written to the F-RAM whenever data is available. And after writing, the radio enters a low power state to await the next wake up.
In addition, the power required to write to F-RAM is considerably lower than writing to EEPROM (approximately 1/60th for 64 kilobits), further reducing the overall power budget. EEPROM in this application would not suffice as it does not have enough endurance and consumes too much power when writing.
Duncan Bennett is a Strategic Marketing Manager at Ramtron International of Colorado Springs, CO. He has over 20 years experience in the semiconductor industry. He started as a design engineer in the industrial control/graphical instrumentation systems field, moving from applications to sales and, finally to marketing. Duncan is responsible at Ramtron for enabling new FRAM applications in the automotive industry and for the definition of new memory products.
Check out Ramtron's web site for details on the company's offerings for the automotive market: Ramtron.com.
Advertisement
