atmega32u4-16mu ATMEL Corporation, atmega32u4-16mu Datasheet - Page 53

• Manufacturer Part Number: atmega32u4-16mu
• Description: Atmega32u4 8-bit Avr Microcontroller With 32k Bytes Of Isp Flash And Usb Controller
• Manufacturer: ATMEL Corporation

8.1
8.1.1
8.2
7766A–AVR–03/08
Internal Voltage Reference
Watchdog Timer
Voltage Reference Enable Signals and Start-up Time
To make use of the Reset Flags to identify a reset condition, the user should read and then
Reset the MCUSR as early as possible in the program. If the register is cleared before another
reset occurs, the source of the reset can be found by examining the Reset Flags.
ATmega32U4 features an internal bandgap reference. This reference 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
reference is on during the following situations:
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 Comparator 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 8-4.
Note:
ATmega32U4 has an Enhanced Watchdog Timer (WDT). The main features are:
•
•
Symbol
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 the
3. When the ADC is enabled.
Clocked from separate On-chip Oscillator
3 Operating modes
V
t
I
– Interrupt
– System Reset
– Interrupt and System Reset
BG
BG
BG
ACBG bit in ACSR).
1. Values are guidelines only. Actual values are TBD.
Parameter
Bandgap reference voltage
Bandgap reference start-up time
Bandgap reference current
consumption
Internal Voltage Reference Characteristics
Table
8-4. To save power, the reference is not always turned on. The
Condition
TBD
TBD
TBD
(1)
TBD
Min
Typ
1.1
40
10
ATmega32U4
Max
TBD
TBD
70
Units
µA
µs
V
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