ATmega165 datasheet(40/336 Pages) ATMEL

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ATmega165/V

2573G–AVR–07/09

External Reset

An External Reset is generated by a low level on the RESET pin. Reset pulses longer

than the minimum pulse width (see Table 16) will generate a reset, even if the clock is

not running. Shorter pulses are not guaranteed to generate a reset. When the applied

signal reaches the Reset Threshold Voltage – V

RST – on its positive edge, the delay

counter starts the MCU after the Time-out period – t

TOUT – has expired.

Figure 17. External Reset During Operation

Brown-out Detection

ATmega165 has an On-chip Brown-out Detection (BOD) circuit for monitoring the V

level during operation by comparing it to a fixed trigger level. The trigger level for the

BOD can be selected by the BODLEVEL Fuses. 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- = VBOT - VHYST/2.

Note:

1. VBOT may be below nominal minimum operating voltage for some devices. For

devices where this is the case, the device is tested down to VCC = VBOT during the

production test. This guarantees that a Brown-Out Reset will occur before V

CC drops

to a voltage where correct operation of the microcontroller is no longer guaranteed.

The test is performed using BODLEVEL = 110 for ATmega169V.

Table 17. BODLEVEL Fuse Coding(1)

BODLEVEL 2..0 Fuses

Min V

BOT

Typ V

BOT

Max V

BOT

Units

111

BOD Disabled

110

1.7

1.8

2.0

101

2.5

2.7

2.9

100

4.1

4.3

4.5

011

Reserved

010

001

000

Table 18. Brown-out Characteristics

Symbol

Parameter

Min

Typ

Max

Units

HYST

Brown-out Detector Hysteresis

BOD

Min Pulse Width on Brown-out Reset

µs

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