|Dual Voltage Supervisory Circuits with I2C Serial 2k-bit CMOS EEPROM FEATURES
s Precision VCC power supply voltage monitor s Low power CMOS technology s 16-Byte page write buffer
s Built-in inadvertent write protection s 1,000,000 Program/Erase cycles s Manual reset capability s 100 year data retention s 8-pin DIP, SOIC, TSSOP, MSOP or TDFNs Watchdog timer (CAT1027 only) s Active high or low reset
The CAT1026 and CAT1027 are complete memory and supervisory solutions for microcontroller-based systems. A 2k-bit serial EEPROM memory and a system power supervisor with brown-out protection are integrated together in low power CMOS technology. Memory interface is via 400kHz I2C bus. The CAT1026 and CAT1027 provide a precision VCC sense circuit with five reset threshold voltage options that support 5V, 3.3V and 3V systems. The power supply monitor and reset circuit protects memory and systems controllers during power up/down and against brownout conditions. If power supply voltages are out of tolerance reset signals become active preventing the system microcontroller, ASIC, or peripherals from operating. used as an input for push-button manual reset capability. The CAT1026 and CAT1027 provide an auxiliary voltage sensor input, VSENSE, which is used to monitor a second system supply. The auxiliary high impedance comparator drives the open drain output, VLOW, whenever the sense voltage is below 1.25V threshold. The CAT1027 is designed with a 1.6 second watchdog timer circuit that resets a system to a known state if software or a hardware glitch halts or "hangs" the system. The CAT1027 features a watchdog timer interrupt input, WDI.
The on-chip 2k-bit EEPROM memory features a 16-byte 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. The CAT1026 features two open drain reset outputs: one (RESET) drives high and the other (RESET) drives Available packages include 8-pin DIP and surface mount, low whenever VCC falls below the threshold. Reset 8-pin SO, 8-pin TSSOP, 8-pin TDFN and 8-pin MSOP outputs become inactive typically 200 ms after the packages. The TDFN package thickness is 0.8mm supply voltage exceeds the reset threshold value. With maximum. TDFN footprint options are or 3x4.9mm both active high and low reset signals, interface to (MSOP pad layout). microcontrollers and other ICs is simple. CAT1027 has only a RESET output. In addition, the RESET pin can be2004 by Catalyst Semiconductor, Inc. Characteristics subject to change without notice
EXTERNAL LOAD DOUT ACK VCC VSS WORD ADDRESS BUFFERS COLUMN DECODERS SENSE AMPS SHIFT REGISTERS
RESET Threshold Options Part Dash Minimum Maximum Number Threshold
HIGH VOLTAGE/ TIMING CONTROL STATE COUNTERS
DIP Package (P, L) SOIC Package (S, V) TSSOP Package (U, Y) MSOP Package (R, Z)
(Bottom View) TDFN Package: 4.9mm 0.8mm maximum height (RD2, ZD2)
(Bottom View) TDFN Package: 3mm 0.8mm maximum height (RD4, ZD4)
RESET/RESET: RESET OUTPUTS (RESET CAT1026 Only) These are open drain pins and RESET can be used as a manual reset trigger input. By forcing a reset condition on the pin the device will initiate and maintain a reset condition. The RESET pin must be connected through a pull-down resistor, and the RESET pin must be connected through a pull-up resistor. SDA: SERIAL DATA ADDRESS The bidirectional serial data/address pin is used to transfer all data into and out of the device. The SDA pin is an open drain output and can be wire-ORed with other open drain or open collector outputs. SCL: SERIAL CLOCK Serial clock input. VSENSE: AUXILIARY VOLTAGE MONITOR INPUT The VSENSE input is a second voltage monitor which is compared against CAT1026 and CAT1027 internal reference voltage of 1.25V typically. Whenever the input voltage is lower than 1.25V, the open drain VLOW output will be driven low. An external resistor divider is used to set the voltage level to be sensed. Connect VSENSE to VCC if unused. VLOW: AUXILIARY VOLTAGE MONITOR OUTPUT This open drain output goes low when VSENSE is less than 1.25V and goes high when VSENSE exceeds the reference voltage. WDI (CAT1027 Only): WATCHDOG TIMER INTERRUPT Watchdog Timer Interrupt Input is used to reset the watchdog timer. If a transition from high to low or low to high does not occur every 1.6 seconds, the RESET outputs will be driven active.
Active Low Reset Input/Output Ground Serial Data/Address Clock Input Active High Reset Output (CAT1026 only) Power Supply Auxiliary Voltage Monitor Input Auxiliary Voltage Monitor Output Watchdog Timer Interrupt (CAT1027 only)
Device Manual Reset Input Pin Watchdog Monitor Pin SDA WDI Write Protection Pin Independent Auxiliary Voltage Sense RESET: Active High and LOW EEPROM
For supervisory circuits with embedded 16k EEPROM, please refer to the CAT1161, CAT1162 and CAT1163 data sheets.