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The X4643/5 combines four popular functions, Poweron Reset Control, Watchdog Timer, Supply Voltage Supervision, and Serial EEPROM Memory in one package. 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 oscillator 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 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 set minimum V_CC trip point. RESET/RESET is asserted until V_CC returns to proper operating level and stabilizes. Four industry standard V_TRIP thresholds are available, however, Intersil's unique circuits allow the threshold to be reprogrammed to meet custom requirements or to fine-tune the threshold for applications requiring higher precision.

Key Features

• Selectable watchdog timer
• Low VCC detection and reset assertion
  • Four standard reset threshold voltages
  • Adjust low VCC reset threshold voltage using special programming sequence
  • Reset signal valid to VCC = 1V
• Low power CMOS
  • <20µA max standby current, watchdog on
  • <1µA standby current, watchdog off
  • 3mA active current
• 64Kbits of EEPROM
  • 64-byte page write mode
  • Self-timed write cycle
  • 5ms write cycle time (typical)
• Built-in inadvertent write protection
  • Power-up/power-down protection circuitry
• 400kHz 2-wire interface
• 2.7V to 5.5V power supply operation
• Available packages
  • 8-lead SOIC
  • 8-lead TSSOP

Applications

• Selectable watchdog timer
• Low VCC detection and reset assertion
  • Four standard reset threshold voltages
  • Adjust low VCC reset threshold voltage using special programming sequence
  • Reset signal valid to VCC = 1V
• Low power CMOS
  • <20µA max standby current, watchdog on
  • <1µA standby current, watchdog off
  • 3mA active current
• 64Kbits of EEPROM
  • 64-byte page write mode
  • Self-timed write cycle
  • 5ms write cycle time (typical)
• Built-in inadvertent write protection
  • Power-up/power-down protection circuitry
• 400kHz 2-wire interface
• 2.7V to 5.5V power supply operation
• Available packages
  • 8-lead SOIC
  • 8-lead TSSOP