• Dual voltage monitoring
• Active low reset outputs
• Two standard reset threshold voltages
  • Factory programmable threshold
• Lowline Output
  • zero delayed POR
• Reset signal valid to V_CC = 1V
• System battery switch-over circuitry
• Selectable watchdog timer
  • (0.15s, 0.4s, 0.8s, off)
• 256Kbits of EEPROM
• Built-in inadvertent write protection
  • Power-up/power-down protection circuitry
  • Protect 0, 1/4, 1/2 or all of EEPROM array with programmable Block Lock™ protection
  • In circuit programmable ROM mode
• Minimize EEPROM programming time
  • 64 byte page write mode
  • Self-timed write cycle
  • 5ms write cycle time (typical)
• 400kHz 2-wire Interface
• 2.7V to 5.5V power supply operation
• Available package — 20-lead TSSOP

The Xicor X45620 combines power-on reset control, battery switch circuit, watchdog timer, supply voltage supervision, secondary voltage supervision, block lock protect and serial EEPROM 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 active for a period of time. This allows the power supply and oscillator to stabilize before the processor can execute code.

A system battery switch circuit compares V_CC (V1MON) with V_BATT input and connects V_OUT to whichever is higher. This provides voltage to external SRAM or other circuits in the event of main power failure. The X45620 can drive 50mA from V_CC and 250µA from V_BATT . The device switches to V_BATT when V_CC drops below the low V_CC voltage threshold and VBATT > V_CC.

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 WDO 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 (V1MON) falls below the minimum V_CC trip point (V_TRIP1 ). RESET is asserted until V_CC returns to proper operating level and stabilizes. A second voltage monitor circuit tracks the unregulated supply or monitors a second power supply voltage to provide a power fail warning. Xicor's unique circuits allow the threshold for either voltage monitor to be reprogrammed to meet special needs or to fine-tune the threshold for applications requiring higher precision. (Contact factory for custom V_TRIP options)