ATMEGA48 datasheet(48/374 Pages) ATMEL

48 / 374 page

2545J–AVR–12/06

ATmega48/88/168

Figure 9-5.

Brown-out Reset During Operation

9.6

Watchdog System Reset

When the Watchdog times out, it will generate a short reset pulse of one CK cycle duration. On

the falling edge of this pulse, the delay timer starts counting the Time-out period t

TOUT. Refer to

page 49 for details on operation of the Watchdog Timer.

Figure 9-6.

Watchdog System Reset During Operation

9.7

Internal Voltage Reference

ATmega48/88/168 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.

9.7.1

Voltage Reference Enable Signals and Start-up Time

The voltage reference has a start-up time that may influence the way it should be used. The

start-up time is given in ”System and Reset Characteristics” on page 307. To save power, the

reference is not always turned on. The reference is on during the following situations:

When the BOD is enabled (by programming the BODLEVEL [2:0] Fuses).

When the bandgap reference is connected to the Analog Comparator (by setting the

ACBG bit in ACSR).

When the ADC is enabled.

VCC

RESET

TIME-OUT

INTERNAL

RESET

VBOT-

VBOT+

tTOUT

ATMEGA48 Datasheet(PDF) 48 Page - ATMEL Corporation