AVR523: Migration from ATmega8 to ATmega8A 8-bit Microcontrollers 1 Introduction In order to optimize the manufacturing process and to further reduce current consumption, an optimized version of ATmega8 has been introduced. Application Note The ATmega8A is a functionally identical, drop-in replacement for the ATmega8. All devices are subject to the same qualification process and same set of production tests, but as the manufacturing process is not the same some electrical characteristics differ. ATmega8 and ATmega8A have separate datasheets. This application note outlines the differences between the two devices and the datasheets. There is also a detailed change log to assist the user at the end of the ATmega8A datasheet. Remember to always use the latest revision of the device datasheet. Minor differences in typical characteristics are not discussed in this document as long as the low and high limits remain the same. For detailed information about the typical characteristics, see sections “Electrical Characteristics” and “Typical Characteristics” of the device datasheets. Note: This application note serves as a guide to ease migration. For complete device details, always refer to the most recent version of the ATmega8A datasheet. Rev. 8164A-AVR-05/09 2 Changes in Characteristics This section outlines major differences in characteristics that may have an effect on the application in which the device is used. For detailed information, refer to the most recent version of the device datasheets. 2.1 Current Consumption Active and Idle mode current consumption of the device has been reduced significantly. The tables below present typical current consumption figures at room temperature. All values are taken from device datasheets, unless otherwise noted. Table 2-1. Typical Current Consumption of Device at Room Temperature Mode Active Idle Condition ATmega8 ATmega8A Change VCC=3V, f=4 MHz 3 mA 2mA - 33% VCC=5V , f=8 MHz 11 mA 6 mA - 45% VCC=3V, f=4 MHz 1 mA 0.5 mA - 50% VCC=5V , f=8 MHz 4.5 mA 2.2 mA - 51% 2.2 VOL Levels In Table 2-2 are listed differences in output voltage levels. Table 2-2. Changes to VOL and VOH Levels Symbol VOL Parameter Output Low Voltage (Ports A - G) ATmega8 Condition ATmega8A Units Min Max Min Max IOL=20mA, VCC=5V - 0.7 - 0.9 V IOL=10mA, VCC=3V - 0.5 - 0.6 V 2.3 Voltage Reference Levels In Table 2-3 are listed differences in reference voltage levels. Table 2-3. Changes to Internal Voltage Reference Levels Symbol VINT ATmega8 Parameter Internal Voltage Reference ATmega8A Unit Min Typ Max Min Typ Max 2.3 2.56 2.7 2.3 2.56 2.8 V 3 Datasheet Changes For a summary of changes, see the revision history at the end of the ATmega8A datasheet. 2 AVR523 8164A-AVR-05/09 Disclaimer Headquarters International Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131 USA Tel: 1(408) 441-0311 Fax: 1(408) 487-2600 Atmel Asia Unit 1-5 & 16, 19/F BEA Tower, Millennium City 5 418 Kwun Tong Road Kwun Tong, Kowloon Hong Kong Tel: (852) 2245-6100 Fax: (852) 2722-1369 Atmel Europe Le Krebs 8, Rue Jean-Pierre Timbaud BP 309 78054 Saint-Quentin-enYvelines Cedex France Tel: (33) 1-30-60-70-00 Fax: (33) 1-30-60-71-11 Atmel Japan 9F, Tonetsu Shinkawa Bldg. 1-24-8 Shinkawa Chuo-ku, Tokyo 104-0033 Japan Tel: (81) 3-3523-3551 Fax: (81) 3-3523-7581 Technical Support [email protected] Sales Contact www.atmel.com/contacts Product Contact Web Site www.atmel.com Literature Request www.atmel.com/literature Disclaimer: The information in this document is provided in connection with Atmel products. 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