AT90PWM216-16SE ATMEL [ATMEL Corporation], AT90PWM216-16SE Datasheet - Page 49

• Manufacturer Part Number: AT90PWM216-16SE
• Description: 8-bit Microcontroller with 16K Bytes In-System Programmable flash
• Manufacturer: ATMEL [ATMEL Corporation]

9.1
9.1.1
9.1.2
9.2
7710D–AVR–08/09
Internal Voltage Reference
Watchdog Timer
Voltage Reference Enable Signals and Start-up Time
Voltage Reference Characteristics
• Bit 1 – EXTRF: External Reset Flag
This bit is set if an External Reset occurs. The bit is reset by a Power-on Reset, or by writing a
logic zero to the flag.
• Bit 0 – PORF: Power-on Reset Flag
This bit is set if a Power-on Reset occurs. The bit is reset only by writing a logic zero to the flag.
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.
AT90PWM216/316 features an internal bandgap reference. This reference is used for Brown-
out Detection. The V
from the internal bandgap reference. In order to use the internal Vref, it is necessary to configure
it thanks to the REFS1 and REFS0 bits in the ADMUX register and to set an analog feature
which requires it.
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 or the DAC,
the user must always allow the reference to start up before the output from the Analog Compar-
ator or ADC or DAC 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 9-4.
Note:
AT90PWM216/316 has an Enhanced Watchdog Timer (WDT). The main features are:
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.
4. When the DAC is enabled.
Symbol
V
t
I
BG
BG
BG
ACBG bit in ACSR).
1. Values are guidelines only.
Parameter
Bandgap reference voltage
Bandgap reference start-up time
Bandgap reference current
consumption
Internal Voltage Reference Characteristics
REF
2.56V reference to the ADC, DAC or Analog Comparators is generated
Table
9-4. To save power, the reference is not always turned on. The
Condition
(1)
AT90PWM216/316
Min.
Typ.
1.1
40
15
Max.
Units
µA
µs
V
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