MEGA128CAN Datasheet, PDF (50/413 Pages) ATMEL Corporation – Microcontroller WITH 128K BYTES OF ISP FLASH AND CAN CONTROLLER

Figure 26. External Reset During Operation
CC
Brown-out Detection
AT90CAN128 has an On-chip Brown-out Detection (BOD) circuit for monitoring the V_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+ = V_BOT + V_HYST/2 and V_BOT- = V_BOT - V_HYST/2.
Table 20. BODLEVEL Fuse Coding⁽¹⁾
BODLEVEL 2..0 Fuses
111
Min V_BOT
Typ V_BOT
Max V_BOT
BOD Disabled
Units
110
4.1
V
101
4.0
V
100
3.9
V
011
3.8
V
010
2.7
V
001
2.6
V
000
2.5
V
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 V_CC = V_BOT 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 = 010 for Low Operating Voltage and
BODLEVEL = 101 for High Operating Voltage .
Table 21. Brown-out Characteristics
Symbol Parameter
Min.
Typ.
Max. Units
V_HYST
Brown-out Detector Hysteresis
70
mV
t_BOD
Min Pulse Width on Brown-out Reset
2
µs
When the BOD is enabled, and V_CC decreases to a value below the trigger level (V_BOT-
in Figure 27), the Brown-out Reset is immediately activated. When V_CC increases above
the trigger level (V_BOT+ in Figure 27), the delay counter starts the MCU after the Time-
out period t_TOUT has expired.
50 AT90CAN128
4250E–CAN–12/04