ATmega16M1 datasheet(49/365 Pages) ATMEL

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7647F–AVR–04/09

ATmega16/32/64/M1/C1

7.2.3

Brown-out Detection

ATmega16/32/64/M1/C1 has an On-chip Brown-out Detection (BOD) circuit for monitoring the

CC 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+ =

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

Notes:

1. V

BOT 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 guar-

antees 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 = 010 for Low Operating Voltage and BODLEVEL = 101 for High Operating Volt-

age .

2. Values are guidelines only.

Notes:

1. Values are guidelines only.

When the BOD is enabled, and V

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

7-5 on page 50), the Brown-out Reset is immediately activated. When V

CC increases above the

trigger level (V

BOT+ in Figure 7-5 on page 50), the delay counter starts the MCU after the

Time-out period t

TOUT 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 7-3.

Table 7-2.

BODLEVEL Fuse Coding

(1)(2)

BODLEVEL 2..0 Fuses

Typ V

BOT

Units

111

Disabled

110

4.5

011

4.4

100

4.3

010

4.2

001

2.8

101

2.7

000

2.6

Table 7-3.

Brown-out Characteristics(1)

Symbol

Parameter

Min.

Typ.

Max.

Units

VHYST

Brown-out Detector Hysteresis

tBOD

Min Pulse Width on Brown-out Reset

µs

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