Replaces X25643/X25645
X5643/X5645
CPU Supervisor with 64Kbit SPI EEPROM
FEATURES
• Selectable watchdog timer
• Low V
CC
detection and reset assertion
—Five standard reset threshold voltages
—Re-program low V
CC
reset threshold voltage
using special programming sequence
—Reset signal valid to V
CC
= 1V
• Determine watchdog or low voltage reset with a
volatile flag bit
• Long battery life with low power consumption
—<50µA max standby current, watchdog on
—<1µA max standby current, watchdog off
—<400µA max active current during read
• 64Kbits of EEPROM
• Built-in inadvertent write protection
—Power-up/power-down protection circuitry
—Protect 0, 1/4, 1/2 or all of EEPROM array with
Block Lock
™
protection
—In circuit programmable ROM mode
• 2MHz SPI interface modes (0,0 & 1,1)
• Minimize EEPROM programming time
—32-byte page write mode
—Self-timed write cycle
—5ms write cycle time (typical)
• 2.7V to 5.5V and 4.5V to 5.5V power supply
operation
• Available packages
—8-lead PDIP, 14-lead SOIC
BLOCK DIAGRAM
Watchdog Transition
Detector
WP
SI
SO
SCK
CS/WDI
Data
Register
Command
Decode &
Control
Logic
V
CC
Threshold
Reset logic
Protect Logic
RESET/RESET
Status
Register
EEPROM Array
16Kbits
16Kbits
32Kbits
Reset &
Watchdog
Timebase
Watchdog
Timer Reset
DESCRIPTION
These devices combine 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 sys-
tem cost, reduces board space requirements, 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
standard V
TRIP
thresholds are available, however,
Xicor’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.
X5643 = RESET
X5645 = RESET
V
CC
V
TRIP
+
-
Power On and
Low Voltage
Reset
Generation
REV 1.1.1 3/5/01
www.xicor.com
Characteristics subject to change without notice.
1 of 19
XICOR [ XICOR INC. ]
