X4003/X4005
CPU Supervisor
FEATURES
DESCRIPTION
• Selectable watchdog timer
—Select 200ms, 600ms, 1.4s, off
These devices combine three popular functions, Power-
on Reset Control, Watchdog Timer, and Supply Voltage
Supervision. This combination lowers system cost,
reduces board space requirements, and increases
reliability.
• Low V
detection and reset assertion
CC
—Five standard reset threshold voltages
nominal 4.62V, 4.38V, 2.92V, 2.68V, 1.75V
—Adjust low V
special programming sequence
—Reset signal valid to V = 1V
reset threshold voltage using
CC
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.
CC
• Low power CMOS
—12µA typical standby current, watchdog on
—800nA typical standby current watchdog off
—3mA active current
The Watchdog Timer provides an independent
protection mechanism for microcontrollers. When the
microcontroller fails to restart a timer within a select-
able 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.
• 400kHz I2C interface
• 1.8V to 5.5V power supply operation
• Available packages
—8-lead SOIC
—8-lead MSOP
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 minimum V trip
CC
CC
returns to
point. RESET/RESET is asserted until V
CC
proper operating level and stabilizes. Five industry stan-
dard V thresholds are available; however, Xicor’s
TRIP
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
Watchdog
Timer Reset
WP
RESET (X4003)
RESET (X4005)
Data
Register
SDA
Control
Register
Command
Decode &
Control
Reset &
Watchdog
Timebase
SCL
Logic
V
Threshold
CC
Reset logic
Power on and
Low Voltage
V
Reset
Generation
+
-
CC
V
TRIP
Characteristics subject to change without notice. 1 of 18
REV 1.1.3 4/30/02
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