AT90PWM81 View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
'AT90PWM81' PDF : 325 Pages View PDF
AT90PWM81/161
7.1.5
Brown-out Detection
AT90PWM81/161 has an On-chip Brown-out Detection (BOD) circuit for monitoring the VCC 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
VBOT+ = VBOT + VHYST/2 and VBOT- = VBOT - VHYST/2.
Table 7-2. BODLEVEL fuse coding (1)(2).
BODLEVEL 2..0 fuses
111
Min VBOT
Typ VBOT
Max VBOT
Forbidden, BOD must be enabled
Units
110
1.8
101 (default configuration)
2.7
100
3.9
4.3
4.6
011
2.3
V
010
2.2
001
1.9
000
2.5
2.0
2.9
Notes:
1. VBOT 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 VCC drops to a voltage where correct
operation of the microcontroller is no longer guaranteed. The test is performed using
BODLEVEL = 010 for Low Operating Voltageand BODLEVEL = 101 for High Operating
Voltage.
2. Values are guidelines only.
Table 7-3. Brown-out characteristics (1).
Symbol Parameter
VHYST
tBOD
Brown-out detector hysteresis
Minimum pulse width on brown-out reset
Minimum
Typical
70
2
Maximum
Units
mV
µs
Notes: 1. Values are guidelines only.
When VCC decreases to a value below the trigger level (VBOT- in Figure 7-5 on page 54), the
Brown-out Reset is immediately activated. When VCC increases above the trigger level (VBOT+ in
Figure 7-5 on page 54), the delay counter starts the MCU after the Time-out period tTOUT has
expired.
The BOD circuit will only detect a drop in VCC if the voltage stays below the trigger level for lon-
ger than tBOD given in Table 7-3.
53
7734Q–AVR–02/12
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