Migration from ATmega645/6450/649/6490 to

Atmel AVR534: Migration from
ATmega645/6450/649/6490 to
ATmega645P/6450P/649P/6490P
1 Introduction
In order to optimize the manufacturing process and to further reduce current
consumption, an optimized version of Atmel® ATmega645/6450/649/6490 has
been introduced.
8-bit Atmel
Microcontrollers
Application Note
The Atmel ATmega645P/6450P/649P/6490P is an upwards compatible, drop-in
replacement for the ATmega645/6450/649/6490. All devices are subject to the
same qualification process and same set of production tests, but some electrical
characteristics differ. The ATmega645P/6450P/649P/6490P devices are
picoPower® megaAVR® microcontrollers and have lower power consumption and
additional power saving features compared to the ATmega645/6450/649/6490.
ATmega645/6450/649/6490 and ATmega645P/6450P/649P/6490P 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 ATmega645P/6450P/649P/6490P 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
ATmega645P/6450P/649P/6490P datasheet.
Rev. 8421A-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 ATmega645P/6450P/649P/6490P.
Table 2-1. Power-on reset threshold voltage.
ATmega645/6450/649/6490
Symbol
ATmega645P/6450P/649P/6490P
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 Low frequency crystal oscillator
In ATmega645P/6450P/649P/6490P 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 ATmega645P/6450P/649P/6490P lowfrequency oscillator is typically 6pF, but the tracks to the crystal will add some
additional capacitance. Table 2-2 shows the ESR recommendations for
ATmega645P/6450P/649P/6490P.
Table
2-2.
ESR
recommendation
ATmega645P/6450P/649P/6490P.
Note:
for
32.768kHz
crystals
Crystal CL [pF]
Maximum ESR (1) [kΩ]
6.5
75
9.0
65
12.5
30
for
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 2-3.
Table 2-3. Startup times with 32.768kHz crystals.
Startup time (1) [ms]
ATmega645/6450/649/6490
Startup time (1) [ms]
ATmega645P/6450P/649P/6490P
6.5
-
600
9.0
300
700
12.5
400
1700
Crystal CL [pF]
Note:
2
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.
Atmel AVR534
8421A-AVR-11/11
Atmel AVR534
3 Signature bytes
Table 3-1 summarizes the differences between the signature bytes of Atmel
ATmega645/6450/649/6490 and Atmel ATmega645P/6450P/649P/6490P.
Table 3-1. Device and JTAG ID.
Signature bytes address
JTAG
Part
0x000
0x001
0x002
Part number
Manufacture ID
ATmega645
0x1E
0x96
0x05
9605
0x1F
ATmega645P
0x1E
0x96
0x0D
960D
0x1F
ATmega6450
0x1E
0x96
0x06
9606
0x1F
ATmega6450P
0x1E
0x96
0x0E
960E
0x1F
ATmega649
0x1E
0x96
0x03
9603
0x1F
ATmega649P
0x1E
0x96
0x0B
960B
0x1F
ATmega6490
0x1E
0x96
0x04
9604
0x1F
ATmega6490P
0x1E
0x96
0x0C
960C
0x1F
3
8421A-AVR-11/11
4 Datasheet changes
For a summary of changes, see the revision history at the end of the Atmel
ATmega645P/6450P/649P/6490P datasheet.
4
Atmel AVR534
8421A-AVR-11/11
Atmel AVR534
5 Appendix A
Table 5-1 is a selection of crystals that meet the ESR requirements of the Atmel
ATmega645P/6450P/649P/6490P. 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 5-1. Examples of crystals compliant with ATmega645P/6450P/649P/6490P low-frequency crystal oscillator.
Mounting
Frequency tolerance
(SMD/HOLE)
[±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
8421A-AVR-11/11
Mounting
Frequency tolerance
(SMD/HOLE)
[±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 AVR534
8421A-AVR-11/11
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8421A-AVR-11/11