ATMEGA2561V ATMEL [ATMEL Corporation], ATMEGA2561V Datasheet - Page 61

• Manufacturer Part Number: ATMEGA2561V
• Description: 8-bit Microcontroller with 64K/128K/256K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

Watchdog Reset
Internal Voltage
Reference
Voltage Reference Enable
Signals and Start-up Time
2549K–AVR–01/07
When the Watchdog times out, it will generate a short reset pulse of one CK cycle dura-
tion. On the falling edge of this pulse, the delay timer starts counting the Time-out period
t
Timer.
Figure 29. Watchdog Reset During Operation
ATmega640/1280/1281/2560/2561 features an internal bandgap reference. This refer-
ence is used for Brown-out Detection, and it can be used as an input to the Analog
Comparator or the ADC.
The voltage reference has a start-up time that may influence the way it should be used.
The start-up time is given in Table 29. To save power, the reference is not always turned
on. The reference is on during the following situations:
1. When the BOD is enabled (by programming the BODLEVEL [2:0] Fuse).
2. When the bandgap reference is connected to the Analog Comparator (by setting
3. When the ADC is enabled.
Thus, when the BOD is not enabled, after setting the ACBG bit or enabling the ADC, the
user must always allow the reference to start up before the output from the Analog Com-
parator or ADC is used. To reduce power consumption in Power-down mode, the user
can avoid the three conditions above to ensure that the reference is turned off before
entering Power-down mode.
Table 29. Internal Voltage Reference Characteristics
Note:
TOUT
Symbol
V
t
I
the ACBG bit in ACSR).
BG
BG
BG
. See “Watchdog Timer” on page 53. for details on operation of the Watchdog
CC
1. Values are guidelines only. Actual values are TBD.
Parameter
Bandgap reference voltage
Bandgap reference start-up time
Bandgap reference current
consumption
ATmega640/1280/1281/2560/2561
CK
Condition
TBD
TBD
TBD
(1)
TBD
Min
Typ
1.1
40
10
Max
TBD
TBD
70
Units
µA
µs
V
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