4K
X4043/45
CPU Supervisor with 4Kbit EEPROM
512 x 8 Bit
FEATURES
• Selectable watchdog timer
• Low V
CC
detection and reset assertion
—Five 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
• 4Kbits of EEPROM
—16-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 16, 32, 64 or 128 bytes
of EEPROM array with Block Lock
™
protection
• 400kHz 2-wire interface
• 2.7V to 5.5V power supply operation
• Available packages
—8-lead SOIC
—8-lead MSOP
—8-lead PDIP
DESCRIPTION
The X4043/45 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 protection
mechanism for microcontrollers. When the microcon-
troller 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 minimum V
CC
trip
point. RESET/RESET is asserted until V
CC
returns to
proper operating level and stabilizes. Five industry stan-
dard V
TRIP
thresholds are available, however, Xicor’s
unique circuits allow the threshold to be reprogrammed
to meet custom requirements or to fine-tune the thresh-
old for applications requiring higher precision.
BLOCK DIAGRAM
Watchdog Transition
Detector
WP
SDA
Data
Register
Command
Decode &
Control
Logic
V
CC
Threshold
Reset logic
Block Lock Control
Protect Logic
Status
Register
EEPROM Array
2Kbits 1Kb 1Kb
RESET (X4043)
RESET (X4045)
Reset &
Watchdog
Timebase
Watchdog
Timer Reset
SCL
V
CC
V
TRIP
+
-
Power on and
Low Voltage
Reset
Generation
REV 1.1.17 9/14/01
www.xicor.com
Characteristics subject to change without notice.
1 of 25
XICOR [ XICOR INC. ]
