X4003/X4005
CPU Supervisor
FEATURES
• Selectable watchdog timer
—Select 200ms, 600ms, 1.4s, off
• Low V
CC
detection and reset assertion
—Five standard reset threshold voltages
nominal 4.62V, 4.38V, 2.92V, 2.68V, 1.75V
—Adjust low V
CC
reset threshold voltage using
special programming sequence
—Reset signal valid to V
CC
= 1V
• Low power CMOS
—12µA typical standby current, watchdog on
—800nA typical standby current watchdog off
—3mA active current
• 400kHz I
2
C interface
• 1.8V to 5.5V power supply operation
• Available packages
—8-lead SOIC
—8-lead MSOP
DESCRIPTION
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.
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
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.
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
V
CC
V
TRIP
+
-
Power on and
Low Voltage
Reset
Generation
Watchdog
Timer Reset
RESET (X4003)
Control
Register
Reset &
Watchdog
Timebase
RESET (X4005)
SCL
REV 1.1.3 4/30/02
www.xicor.com
Characteristics subject to change without notice.
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XICOR [ XICOR INC. ]
