Preliminary Information
128K
16K x 8 Bit
X4283/85
CPU Supervisor with 128K EEPROM
FEATURES
DESCRIPTION
• Selectable watchdog timer
The X4283/85 combines four popular functions,
Power-on Reset Control, Watchdog Timer, Supply Volt-
age Supervision, and Block Lock protect serial
EEPROM memory in one package. This combination
lowers system cost, reduces board space require-
ments, and increases reliability.
• Low V
detection and reset assertion
CC
—Four standard reset threshold voltages
—Adjust low V reset threshold voltage using
CC
special programming sequence
—Reset signal valid to V = 1V
CC
• Low power CMOS
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.
—<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
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.
—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
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
CC
CC
returns
trip point. RESET/RESET is asserted until V
CC
—8-lead SOIC
—8-lead TSSOP
to proper operating level and stabilizes. Four industry
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
V
Threshold
CC
Reset logic
Power on and
Low Voltage
Reset
+
-
V
CC
Generation
V
TRIP
Characteristics subject to change without notice. 1 of 22
REV 1.17 11/27/00
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