AVR540: Migration from ATmega325/3250/329/3290 to ATmega325A/3250A/329A/3290A 1 Introduction The Atmel® AVR® ATmega325A/3250A/329A/3290A is a functionally identical, drop-in replacement for the ATmega325/3250/329/3290. 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. 8-bit Microcontrollers Application Note ATmega325/3250/329/3290 and ATmega325A/3250A/329A/3290A 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 ATmega325A/3250A/329A/3290A 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 ATmega325A/3250A/329A/3290A data sheet. Rev. 8343A-AVR-09/10 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 data sheets. 2.1 Reset The table below summarizes the differences between the ATmega325/3250/329/3290 and ATmega325A/3250A/329A/3290A reset threshold parameters. Table 2-4. Power-On Reset threshold voltage Symbol ATmega325/3250/329/3290 ATmega325A/3250A/329A/3290A 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 The table below summarizes the differences between the ATmega325/3250/329/3290 and ATmega325A/3250A/329A/3290A JTAG IDs. Table 3-1. JTAG ID JTAG ID Part Part Number Manufacture ID ATmega325 9505 0x1F ATemga325A 950D 0x1F ATmega3250 9506 0x1F ATmega3250A 950E 0x1F ATmega329 9503 0x1F ATmega329A 950B 0x1F ATemga3290 9504 0x1F ATmega3290A 950C 0x1F 2.3 Low-frequency Crystal Oscillator In ATmega325A/3250A/329A/3290A, the crystal driver strength of the low frequency crystal oscillator is reduced compared to the ATmega325/3250/329/3290. 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 ATmega325A/3250A/329A/3290A lowfrequency oscillator is typically 6pF, but the tracks to the crystal will add some additional capacitance. Table 2-5 shows the ESR recommendations for ATmega325A/3250A/329A/3290A. 2 AVR540 8343A-AVR-10/10 AVR540 Table 2-5. ESR recommendation ATmega325A/3250A/329A/3290A. Note: for 32.768kHz crystals Crystal CL [pF] Max ESR1 [kΩ] 6.5 75 9 65 12.5 30 for 1. The values stated are for an oscillator allowance safety margin of 5. Because 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 2-6. Table 2-6. Startup times with 32.768kHz crystals. Crystal CL [pF] Startup time2 [ms] Atmega644 Startup time2 [ms] Atmega644A 6.5 - 600 9 300 700 12.5 400 1700 Note: 2. 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 8343A-AVR-10/10 Appendix A Table 4-1 is a selection of crystals that ATmega644A. The crystals are listed based tested with the actual device. Any other requirements can also be used. Availability investigated. meet the ESR requirements of the on datasheet information, and are not crystal that complies with the ESR and RoHS compliance has not been Table 4-1. Examples of crystals compliant with ATmega48P/88P/168P 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 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 C-MAC ® ® 4 AVR540 8343A-AVR-10/10 AVR540 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 ® 5 8343A-AVR-10/10 Disclaimer Headquarters International Atmel Corporation 2325 Orchard Parkway San Jose, CA 95131 U.S.A. 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