1
®
FN8121.1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Copyright Intersil Americas Inc. 2005-2006. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
X4283, X4285
128K, 16K x 8 Bit
CPU Supervisor with 128K EEPROM
FEATURES
• Selectable watchdog timer
•Low V
CC
detection and reset assertion
—Four standard reset threshold voltages
—Adjust low V
CC
reset threshold voltage using
special programming sequence
—Reset signal valid to V
CC
= 1V
• Low power CMOS
—<20µA max standby current, watchdog on
—<1µA standby current, watchdog OFF
—3mA active current
• 128Kbits of EEPROM
—64 byte page write mode
—Self-timed write cycle
—5ms write cycle time (typical)
• Built-in inadvertent write protection
—Power-up/power-down protection circuitry
—Protect 0, 1/4, 1/2, all or 64, 128, 256 or 512
bytes of EEPROM array with programmable
Block Lock
™
protection
• 400kHz 2-wire interface
• 2.7V to 5.5V power supply operation
• Available packages
—8 Ld SOIC
—8 Ld TSSOP
• Pb-free plus anneal available (RoHS compliant)
DESCRIPTION
The X4283, X4285 combines four popular functions,
Power-on Reset Control, Watchdog Timer, Supply
Voltage Supervision, and Block Lock protect serial
EEPROM memory in one package. This combination
lowers system cost, reduces board space require-
ments, and increases reliability.
Applying power to the device activates the power-on
reset circuit which holds RESET
/RESET active for a
period of time. This allows the power supply and oscilla-
tor to stabilize before the processor can execute code.
The Watchdog Timer provides an independent protec-
tion mechanism for microcontrollers. When the micro-
controller fails to restart a timer within a selectable
time out interval, the device activates the
RESET
/RESET signal. The user selects the interval
from three preset values. Once selected, the interval
does not change, even after cycling the power.
The device’s low V
CC
detection circuitry protects the
user’s system from low voltage conditions, resetting
the system when V
CC
falls below the set minimum V
CC
trip point. RESET/RESET is asserted until V
CC
returns
to proper operating level and stabilizes. Four industry
standard Vtrip thresholds are available, however, Inter-
sil’s unique circuits allow the threshold to be repro-
grammed to meet custom requirements or to fine-tune
the threshold for applications requiring higher precision.
BLOCK DIAGRAM
Watchdog
Timer Reset
Data
Register
Command
Decode &
Control
Logic
SDA
SCL
V
CC
Reset &
Watchdog
Timebase
Power-on and
Generation
V
TRIP
+
-
RESET (X4283)
Reset
Low Voltage
Status
Register
Protect Logic
EEPROM Array
Watchdog Transition
Detector
WP
V
CC
Threshold
Reset logic
Block Lock Control
8Kb 4Kb 4Kb
RESET (X4285)
S0
S1
Kb=Kilobyte
Data Sheet May 23, 2006
