X4283, X4285
®
128K, 16K x 8 Bit
Data Sheet
March 29, 2005
FN8121.0
DESCRIPTION
CPU Supervisor with 128K EEPROM
The X4283/85 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.
FEATURES
• Selectable watchdog timer
• Low V detection and reset assertion
CC
—Four standard reset threshold voltages
—Adjust low V reset threshold voltage using
CC
special programming sequence
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.
—Reset signal valid to V = 1V
CC
• 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
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.
—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
The device’s low V
detection circuitry protects the
CC
user’s system from low voltage conditions, resetting
the system when V falls below the set minimum V
™
Block Lock protection
CC
CC
• 400kHz 2-wire interface
• 2.7V to 5.5V power supply operation
• Available packages
—8-lead SOIC
trip point. RESET/RESET is asserted until V returns
CC
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.
—8-lead TSSOP
BLOCK DIAGRAM
Watchdog Transition
Detector
Watchdog
Timer Reset
WP
Protect Logic
RESET (X4283)
RESET (X4285)
Data
Register
SDA
Status
Register
EEPROM Array
Command
Reset &
Watchdog
Timebase
SCL
Decode &
Control
Logic
S0
S1
VCC Threshold
Reset logic
Power-on and
Low Voltage
+
-
VCC
Reset
Kb=Kilobyte
Generation
VTRIP
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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1
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