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CAT1021, CAT1022, CAT1023
Supervisory Circuits with I2C Serial 2k-bit CMOS EEPROM, Manual Reset
and Watchdog Timer
TM
FEATURES
■ Precision power supply voltage monitor
— 5V, 3.3V and 3V systems
— Five threshold voltage options
■ Watchdog timer
■ Built-in inadvertent write protection
— WP pin (CAT1021)
■ 1,000,000 Program/Erase cycles
■ Manual reset input
■ Active high or low reset
— Valid reset guaranteed at VCC = 1 V
■ 400kHz I2C bus
■ 100 year data retention
■ 8-pin DIP, SOIC, TSSOP, MSOP or TDFN
(3 x 3 mm foot-print) packages
— TDFN max height is 0.8mm
■ 3.0V to 5.5V operation
■ Industrial and extended temperature ranges
■ Low power CMOS technology
■ 16-Byte page write buffer
DESCRIPTION
The CAT1021, CAT1022 and CAT1023 are complete The power supply monitor and reset circuit protect memory
memory and supervisory solutions for microcontroller- and system controllers during power up/down and against
based systems. A 2k-bit serial EEPROM memory and a brownout conditions. Five reset threshold voltages support
system power supervisor with brown-out protection are 5V, 3.3V and 3V systems. If power supply voltages are out
integrated together in low power CMOS technology. of tolerance reset signals become active, preventing the
Memory interface is via a 400kHz I2C bus.
systemmicrocontroller, ASICorperipheralsfromoperating.
Reset signals become inactive typically 200 ms after the
supply voltage exceeds the reset threshold level. With both
activehighandlowresetsignals,interfacetomicrocontrollers
and other ICs is simple. In addition, the RESET pin or a
separate input, MR, can be used as an input for push-button
manual reset capability.
The CAT1021 and CAT1023 provide a precision VCC
sense circuit and two open drain outputs: one (RESET)
drives high and the other (RESET) drives low whenever
VCC fallsbelowtheresetthresholdvoltage.TheCAT1022
has only a RESET output and does not have a Write
Protect input. The CAT1021 also has a Write Protect
input (WP). Write operations are disabled if WP is The on-chip, 2k-bit EEPROM memory features a 16-byte
connected to a logic high.
page. In addition, hardware data protection is provided by a
VCC sense circuit that prevents writes to memory whenever
VCC falls below the reset threshold or until VCC reaches the
reset threshold during power up.
Allsupervisorshavea1.6secondwatchdogtimercircuit
that resets a system to a known state if software or a
hardware glitch halts or “hangs” the system. For the
CAT1021 and CAT1022, the watchdog timer monitors Available packages include an 8-pin DIP, 8-pin SOIC, 8-pin
theSDAsignal.TheCAT1023hasaseparatewatchdog TSSOP, 8-pin TDFN and 8-pin MSOP. The TDFN package
timer interrupt input pin, WDI.
thickness is 0.8mm maximum. TDFN footprint options are
3x3mm.
© 2004 by Catalyst Semiconductor, Inc.
Doc No. 3009, Rev. K
Characteristics subject to change without notice
CATALYST [ CATALYST SEMICONDUCTOR ]
