Rainbow Electronics ATtiny15L - Manual (Page 17)

17
ATtiny15L
1187E–AVR–06/02
Brown-out Detection ATtiny15L has an On-chip Brown-out Detection (BOD) circuit for monitoring the V
CC
level during the operation. The BOD circuit can be enabled/disabled by the fuse
BODEN. When BODEN is enabled (BODEN programmed), and V
CC
decreases below
the trigger level, the Brown-out Reset is immediately activated. When V
CC
increases
above the trigger level, the Brown-out Reset is deactivated after a delay. The delay is
defined by the user in the same way as the delay of POR signal, in Table 5. 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
of 50 mV to ensure spike-free Brown-out Detection.
The BOD circuit will only detect a drop in V
CC
if the voltage stays below the trigger level
for longer than 3 µs for trigger level 4.0V, 7 µs for trigger level 2.7V (typical values).
Figure 16. Brown-out Reset during Operation (1)
Note: 1. The hysteresis on V
BOT
: V
BOT+
= V
BOT
+ 25 mV, V
BOT-
= V
BOT
- 25 mV.
Watchdog Reset When the Watchdog times out, it will generate a short reset pulse of one CK cycle dura-
tion. On the falling edge of this pulse, the delay timer starts counting the Time-out period
t
TOUT
. Refer to page 34 for details on operation of the Watchdog Timer.
Figure 17. Watchdog Reset during Operation
V
CC
RESET
TIME-OUT
INTERNAL
RESET
V
BOT-
V
BOT+
t
TOUT
1 CK Cycle