AT89LP428 Atmel Corporation, AT89LP428 Datasheet - Page 25

• Manufacturer Part Number: AT89LP428
• Manufacturer: Atmel Corporation

Specifications of AT89LP428

• Flash (kbytes): 4 Kbytes
• Max. Operating Frequency: 25 MHz
• Cpu: 8051-1C
• Max I/o Pins: 30
• Spi: 1
• Uart: 1
• Sram (kbytes): 0.75
• Eeprom (bytes): 512
• Self Program Memory: IAP
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 3
• Isp: SPI/OCD
• Watchdog: Yes

7.2
3654A–MICRO–8/09
Brown-out Reset
Table 7-1.
The AT89LP428/828 has an on-chip Brown-out Detector (BOD) circuit for monitoring the V
level during operation by comparing it to a fixed trigger level. The trigger level V
is nominally 2.2V. The purpose of the BOD is to ensure that if V
speed, the system will gracefully enter reset without the possibility of errors induced by incorrect
execution. A BOD sequence is shown in
trigger level V
trigger level, the start-up timer releases the internal reset after the specified time-out period has
expired
and falling V
Enable Fuse.
The AT89LP428/828 allows for a wide V
cient to prevent incorrect execution if V
as when a 5V supply is coupled with high frequency operation. In such cases an external Brown-
out Reset circuit connected to the RST pin may be required.
Figure 7-3.
SUT Fuse 1
Time-out
Internal
Reset
0
0
1
1
(Table
V
CC
BOD
(See “User Configuration Fuses” on page
BOD
Start-up Timer Settings
Brown-out Detector Reset
7-1). Note that there is approximately 200 mV of hysteresis between the rising
V POR
, the internal reset is immediately activated. When V
thresholds. The Brown-out Detector must be enabled by setting the BOD
SUT Fuse 0
0
1
0
1
Clock Source
Internal RC/External Clock
Crystal Oscillator
Internal RC/External Clock
Crystal Oscillator
Internal RC/External Clock
Crystal Oscillator
Internal RC/External Clock
Crystal Oscillator
BOD
CC
Figure
is lower than the minimum required V
operating range. The on-chip BOD may not be suffi-
7-3. When V
121.)
V BOD
t SUT
CC
CC
decreases to a value below the
fails or dips while executing at
AT89LP428/828
CC
increases above the
t
SUT
BOD
CC
16384
(± 5%) µs
1024
2048
1024
4096
N/A
N/A
16
for the BOD
range, such
25
CC