View detail for Atmel AVR543: Migration from ATmega645/6450/649/6490 to ATmega645A/6450A/649A/6490A

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
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8423A-AVR-11/11