ATmega128 datasheet(53/386 Pages) ATMEL

No. de pieza	ATmega128

Descripción Electrónicos	8-bit Microcontroller with 128K Bytes In-System Programmable Flash

PDF	386 Pages

Scroll/Zoom	100%

Fabricante Electrónico	ATMEL [ATMEL Corporation]

Página de inicio	http://www.atmel.com

Logo

53 / 386 page

2467S–AVR–07/09

ATmega128

Figure 25. External Reset During Operation

Brown-out Detection

ATmega128 has an On-chip Brown-out Detection (BOD) circuit for monitoring the V

CC level dur-

ing operation by comparing it to a fixed trigger level. The trigger level for the BOD can be

selected by the fuse BODLEVEL to be 2.7V (BODLEVEL unprogrammed), or 4.0V (BODLEVEL

programmed). The trigger level has a hysteresis to ensure spike free Brown-out Detection. The

hysteresis on the detection level should be interpreted as V

BOT+ = VBOT + VHYST/2 and VBOT- =

BOT - VHYST/2.

The BOD circuit can be enabled/disabled by the fuse BODEN. When the BOD is enabled

(BODEN programmed), and V

CC decreases to a value below the trigger level (VBOT- in Figure

26), the Brown-out Reset is immediately activated. When V

CC increases above the trigger level

BOT+ in Figure 26), the delay counter starts the MCU after the time-out period tTOUT has

expired.

The BOD circuit will only detect a drop in V

CC if the voltage stays below the trigger level for lon-

ger than t

BOD given in Table 19.

Figure 26. Brown-out Reset During Operation

VCC

RESET

TIME-OUT

INTERNAL

RESET

VBOT-

VBOT+

tTOUT

ATmega128 Datasheet(PDF) 53 Page - ATMEL Corporation