Atmel AVR543: Migration from ATmega645/6450/649/6490 to ATmega645A/6450A/649A/6490A 1 Introduction The Atmel® ATmega645A/6450A/649A/6490A is a functionally identical, drop-in replacement for the Atmel ATmega645/6450/649/6490. All devices are subject to the same qualification process and same set of production tests, but some electrical characteristics differ. 8-bit Atmel Microcontrollers Application Note ATmega645/6450/649/6490 and ATmega645A/6450A/649A/6490A have separate datasheets. This application note outlines the differences between the two devices and between the datasheets. There is also a detailed change log to assist the user at the end of the ATmega645A/6450A/649A/6490A 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 ATmega645A/6450A/649A/6490A datasheet. Rev. 8423A-AVR-11/11 2 Changes in characteristics This section outlines such 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 Reset Table 2-1 summarizes the differences between the reset threshold parameters of Atmel ATmega645/6450/649/6490 and Atmel ATmega645A/6450A/649A/6490A. Table 2-1. Power-on reset threshold voltage. Symbol ATmega645/6450/649/6490 ATmega645A/6450A/649A/6490A Unit Min. Typ. Max. Min. Typ. Max. VPOT rising 0.7 1.0 1.4 1.1 1.4 1.6 V VPOT falling 0.05 0.9 1.3 0.6 1.3 1.6 V 2.2 JTAG ID Table 2-2 summarizes the differences between the ATmega645/6450/649/6490 and ATmega645A/6450A/649A/6490A JTAG IDs. Table 2-2. JTAG ID. JTAG ID Part Part Number Manufacture ID ATmega645 9605 0x1F ATemga645A 960D 0x1F ATmega6450 9606 0x1F ATmega6450A 960E 0x1F ATmega649 9603 0x1F ATmega649A 960B 0x1F ATemga6490 9604 0x1F ATmega6490A 960C 0x1F 2.3 Low frequency crystal oscillator In ATmega645A/6450A/649A/6490A the crystal driver strength of the Low Frequency Crystal Oscillator is reduced compared to the ATmega645/6450/649/6490. This means that when selecting a crystal, its load capacitance and Equivalent Series Resistance (ESR) must be taken into consideration. Both values are specified by the crystal vendor. The internal capacitance of the ATmega645A/6450A/649A/6490A lowfrequency oscillator is typically 6pF, but the tracks to the crystal will add some additional capacitance. Table 2-3 shows the ESR recommendations for ATmega645A/6450A/649A/6490A. 2 Atmel AVR543 8423A-AVR-11/11 Atmel AVR543 Table 2-3. ESR recommendation ATmega645A/6450A/649A/6490A. Note: for 32.768kHz crystals Crystal CL [pF] Max ESR (1) [kΩ] 6.5 75 9.0 65 12.5 30 for Atmel 1. The values stated are for an oscillator allowance safety margin of 5. Since the oscillator’s transconductance is temperature compensated one can use a safety margin of 4, thus giving a max ESR of 90, 80 and 40kΩ respectively. For examples of crystals that comply with the requirements, see Appendix A. The startup times are increased as shown in Table 2-4. Table 2-4. Startup times with 32.768kHz crystals. Crystal CL [pF] Startup time (1) [ms] Atmel ATmega645/6450/649/6490 Startup time (1) [ms] ATmega645A/6450A/649A/6490A 6.5 - 600 9.0 300 700 12.5 400 1700 Note: 1. Crystals usually need ~3000ms before they are completely stable with any oscillator design. The time stated is before the crystal is running with a sufficient amplitude and frequency stability. 3 8423A-AVR-11/11 3 Datasheet changes For a summary of changes, see the revision history at the end of the Atmel ATmega645A/6450A/649A/6490A datasheet. 4 Atmel AVR543 8423A-AVR-11/11 Atmel AVR543 4 Appendix A Table 4-1 is a selection of crystals that meet the ESR requirements of the Atmel ATmega645A/6450A/649A/6490A. The crystals are listed based on datasheet information and are not tested with the actual device. Any other crystal that complies with the ESR requirements can also be used. Availability and RoHS compliance has not been investigated. Table 4-1. Examples of crystals compliant with ATmega645A/6450A/649A/6490A low-frequency crystal oscillator. Mounting (SMD/HOLE) Frequency Tolerance [±ppm] Load Capacitance [pF] Equivalent Series Resistance (ESR) [kΩ] Vendor Type C-MAC WATCH CRYSTALS HOLE 20 6 50 C-MAC 85SMX SMD 20 6 55 C-MAC 90SMX SMD 20 6 60 ECLIPTEK E4WC HOLE 20 6 50 ENDRICH 90SMX SMD 5 6 50 ® EPSON C-001R HOLE 20 6 -> 12.5 (specify) 35 EPSON C-002RX HOLE 20 6 -> 10 (specify) 50 EPSON C-004R HOLE 20 6 -> 10 (specify) 50 EPSON C-005R HOLE 20 6 -> 10 (specify) 50 EPSON MC-30A SMD 20 6 -> 10 (specify) 50 EPSON MC-306 SMD 20 6 -> 10 (specify) 50 EPSON MC-405 SMD 20 6 -> 10 (specify) 50 EPSON MC-406 SMD 20 6 -> 10 (specify) 50 GOLLEDGE GWX HOLE 5 6, 8 or 12.5 35 GOLLEDGE GSWX-26 SMD 10 6 , 8 or 12.5 35 GOLLEDGE GDX1 HOLE 10 6 42 GOLLEDGE GSX-200 SMD 5 6 50 IQD WATCH CRYSTALS HOLE 20 6 50 IQD 90SMX HOLE 10 6 60 IQD 91SMX HOLE 10 6 60 MICROCRYSTAL MS3V-T1R HOLE 20 7 or 9 65 MICROCRYSTAL MS2V-T1R HOLE 20 7 or 9 65 MICROCRYSTAL CC4V-T1A SMD 30 9 65 MICROCRYSTAL CC1V-T1A SMD 30 9 60 MICROCRYSTAL CC7V-T1A SMD 30 9 70 MMD WC26 HOLE 8 8 35 MMD WC38 HOLE 8 8 35 MMD WC155 HOLE 8 8 40 MMD WCSMC SMD 20 6 50 OSCILENT SERIES 111 HOLE 10 6 or 12.5 30 OSCILENT SERIES 112 HOLE 10 6 or 12.5 40 5 8423A-AVR-11/11 Mounting (SMD/HOLE) Frequency Tolerance [±ppm] Load Capacitance [pF] Equivalent Series Resistance (ESR) [kΩ] Vendor Type OSCILENT SERIES 113 HOLE 10 8 40 OSCILENT SERIES 223 SMD 20 6 50 RALTRON SERIES R38 HOLE 5 6 or 12.5 35 RALTRON SERIES R26 HOLE 5 6 or 12.5 35 RALTRON SERIES R145 HOLE 5 8 40 RALTRON SERIES RSE A, B, C, D SMD 20 6 50 SBTRON SBX-13 SMD 20 6 50 SBTRON SBX-20 SMD 20 6 50 SBTRON SBX-21 SMD 20 6 50 SBTRON SBX-24 SMD 20 6 50 SBTRON SBX-23 SMD 20 6 50 SBTRON SBX-22 SMD 20 6 50 SBTRON SBX-14 HOLE 20 6 50 SUNTSU SCT1 HOLE 20 6, 8, 10 or 12.5 40 SUNTSU SCT2 HOLE 20 6, 8, 10 50 SUNTSU SCT3 HOLE 20 6, 8, 10 50 SUNTSU SCP1 SMD 20 6 50 SUNTSU SCT2G SMD 20 6 or 10 50 6 Atmel AVR543 8423A-AVR-11/11 Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131 USA Tel: (+1)(408) 441-0311 Fax: (+1)(408) 487-2600 www.atmel.com Atmel Asia Limited Unit 01-5 & 16, 19F BEA Tower, Milennium City 5 418 Kwun Tong Road Kwun Tong, Kowloon HONG KONG Tel: (+852) 2245-6100 Fax: (+852) 2722-1369 Atmel Munich GmbH Business Campus Parkring 4 D-85748 Garching b. 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