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Power-on Reset
ATtiny26(L)
32
Table 16. Reset Characteristics
Symbol
Parameter
Power-on Reset Threshold
Voltage (rising)
V
POT
Power-on Reset Threshold
Voltage (falling)
V
RESET Pin Threshold Voltage
RST
Minimum pulse width on
t
RST
RESET Pin
Brown-out Reset Threshold
V
(2)
Voltage
BOT
Minimum low voltage period for
t
Brown-out Detection
BOD
V
Brown-out Detector hysteresis
HYST
Notes:
1. The Power-on Reset will not work unless the supply voltage has been below V
(falling)
2. V
may be below nominal minimum operating voltage for some devices. For
BOT
devices where this is the case, the device is tested down to V
production test. This guarantees that a Brown-out Reset will occur before V
to a voltage where correct operation of the microcontroller is no longer guaranteed.
The test is performed using BODLEVEL=1 for ATtiny26L and BODLEVEL=0 for
ATtiny26. BODLEVEL=1 is not applicable for ATtiny26.
See start-up times from reset from "System Clock and Clock Options" on page 22.
When the CPU wakes up from Power-down, only the clock counting part of the start-up
time is used. The Watchdog Oscillator is used for timing the real-time part of the start-up
time.
A Power-on Reset (POR) pulse is generated by an On-chip Detection circuit. The detec-
tion level is defined in Table 16 The POR is activated whenever V
detection level. The POR circuit can be used to trigger the Start-up Reset, as well as
detect a failure in supply voltage.
The Power-on Reset (POR) circuit ensures that the device is reset from Power-on.
Reaching the Power-on Reset threshold voltage invokes a delay counter, which deter-
mines the delay, for which the device is kept in RESET after V
period of the delay counter can be defined by the user through the CKSEL Fuses. The
different selections for the delay period are presented in "System Clock and Clock
Options" on page 22. The RESET signal is activated again, without any delay, when the
V
decreases below detection level.
CC
Condition
(1)
BODLEVEL = 1
BODLEVEL = 0
BODLEVEL = 1
BODLEVEL = 0
Min
Typ
Max
Units
1.4
2.3
V
1.3
2.3
V
0.2
0.9
V
CC
1.5
µs
2.4
2.7
2.9
V
3.7
4.0
4.5
2
µs
2
µs
130
mV
POT
= V
during the
CC
BOT
drops
CC
is below the
CC
rise. The time-out
CC
1477G–AVR–03/05
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