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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.
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
ATmega645A/6450A/649A/6490A datasheet.
refer
to
the
most
recent
version
of
8-bit Atmel
Microcontrollers
Application Note
the
Rev. 8423A-AVR-11/11
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Related Manuals for Atmel ATmega645
Summary of Contents for Atmel ATmega645
- Page 1 The Atmel ATmega645A/6450A/649A/6490A is a functionally identical, drop-in Application Note 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. ATmega645/6450/649/6490 and ATmega645A/6450A/649A/6490A have separate datasheets.
-
Page 2: Low Frequency Crystal Oscillator
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. - Page 3 Table 2-4. Startup times with 32.768kHz crystals. Startup time [ms] Startup time [ms] Crystal CL [pF] Atmel ATmega645/6450/649/6490 ATmega645A/6450A/649A/6490A 12.5 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.
- Page 4 3 Datasheet changes For a summary of changes, see the revision history at the end of the Atmel ATmega645A/6450A/649A/6490A datasheet. Atmel AVR543 8423A-AVR-11/11...
- Page 5 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.
- Page 6 SBX-21 SBTRON SBX-24 SBTRON SBX-23 SBTRON SBX-22 SBTRON SBX-14 HOLE SUNTSU SCT1 HOLE 6, 8, 10 or 12.5 SUNTSU SCT2 HOLE 6, 8, 10 SUNTSU SCT3 HOLE 6, 8, 10 SUNTSU SCP1 SUNTSU SCT2G 6 or 10 Atmel AVR543 8423A-AVR-11/11...
- Page 7 Disclaimer: The information in this document is provided in connection with Atmel products. No license, express or implied, by estoppel or otherwise, to any intellectual property right is granted by this document or in connection with the sale of Atmel products. EXCEPT AS SET FORTH IN THE ATMEL...