Preliminary Information
64K
X4643/5
CPU Supervisor with 64K EEPROM
DESCRIPTION
8K x 8 Bit
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
• 64Kbits 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
• 400kHz 2-wire interface
• 2.7V to 5.5V power supply operation
• Available packages
—8-lead SOIC
—8-lead TSSOP
The X4643/5 combines four popular functions, Power-on
Reset Control, Watchdog Timer, Supply Voltage
Supervision, and Serial EEPROM Memory in one
package. This combination lowers system cost,
reduces board space requirements, and increases reli-
ability.
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 set minimum V
CC
trip
point. RESET/RESET is asserted until V
CC
returns to
proper operating level and stabilizes. Four industry
BLOCK DIAGRAM
Watchdog Transition
Detector
WP
Data
Register
Command
Decode &
Control
Logic
V
CC
Threshold
Reset Logic
Block Lock Control
Protect Logic
Status
Register
EEPROM Array
RESET (X4643/5)
RESET (X4645)
Watchdog
Timer Reset
SDA
SCL
S0
S1
Reset &
Watchdog
Timebase
8Kbit
V
CC
V
TRIP
+
-
Power on and
Low Voltage
Reset
Generation
REV 1.26 4/30/02
www.xicor.com
Characteristics subject to change without notice.
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XICOR [ XICOR INC. ]
