Brown-Out Detection - Atmel ATtiny25 Manual

8.5

Brown-out Detection

ATtiny25/45/85
38
Figure 8-4. External Reset During Operation
CC
ATtiny25/45/85 has an On-chip Brown-out Detection (BOD) circuit for monitoring the V
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
V + V /2 and V
BOT HYST BOT-
Table 8-2. BODLEVEL Fuse Coding
BODLEVEL [2..0] Fuses
111
110
101
100
011
010
001
000
Note: 1. V may be below nominal minimum operating voltage for some devices. For devices where
BOT
this is the case, the device is tested down to V
antees that a Brown-out Reset will occur before V
operation of the microcontroller is no longer guaranteed.
2. Centered value, not tested.
Table 8-3. Brown-out Characteristics
Symbol Parameter
V RAM Retention Voltage
RAM
V Brown-out Detector Hysteresis
HYST
t Min Pulse Width on Brown-out Reset
BOD
Notes: 1. This is the limit to which VDD can be lowered without losing RAM data
= V - V /2.
BOT HYST
(1)
Min V
BOT
1.7
2.5
4.0
(1)
Typ V Max V
BOT
BOD Disabled
1.8 2.0
2.7 2.9
4.3 4.6
(2)
2.3
(2)
2.2
(2)
1.9
(2)
2.0
= V during the production test. This guar-
CC BOT
drops to a voltage where correct
CC
Min Typ
50
50
2
level
CC
=
BOT+
Units
BOT
V
Max Units
mV
mV
µs
7598H–AVR–07/09