DESCRIPTION
   The X40420, X40421 combines power-on reset control, watchdog timer, supply voltage supervision, and secondary supervision, manual reset, and Block Lock™ protect serial EEPROM in one package. This combination lowers system cost, reduces board space requirements, and increases reliability.

FEATURES
• Dual voltage detection and reset assertion
   —Three standard reset threshold settings
      (4.6V/2.9V, 4.6V/2.6V, 2.9V/1.6V)
   —VTRIP2 programmable down to 0.9V
   —Adjust low voltage reset threshold voltages
      using special programming sequence
   —Reset signal valid to VCC = 1V
   —Monitor two voltages or detect power fail
• Battery switch backup
• VOUT: 5mA to 50mA from VCC; or 250µA from
   VBATT
• Fault detection register
• Selectable power-on reset timeout
   (0.05s, 0.2s, 0.4s, 0.8s)
• Selectable watchdog timer interval
   (25ms, 200ms, 1.4s, off)
• Debounced manual reset input
• Low power CMOS
   —25µA typical standby current, watchdog on
   —6µA typical standby current, watchdog off
   —1µA typical battery current in backup mode
• 4Kbits of EEPROM
   —16 byte page write mode
   —Self-timed write cycle
   —5ms write cycle time (typical)
• Built-in inadvertent write protection
   —Power-up/power-down protection circuitry
   —Block lock protect 0 or 1/2, of EEPROM
• 400kHz 2-wire interface
• 2.7V to 5.5V power supply operation
• Available packages
   —14 Ld SOIC, TSSOP
• Pb-free plus anneal available (RoHS compliant)
• Monitor voltages: 5V to 1.6V
• Memory security
• Battery switch backup
• VOUT 5mA to 50mA

APPLICATIONS
• Communications equipment
   —Routers, hubs, switches
   —Disk arrays
• Industrial systems
   —Process control
   —Intelligent instrumentation
• Computer systems
   —Desktop computers
   —Network servers