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DS1819A, DS1819B, DS1819C：5 Volt and 3.3 Volt MicroMonitor

The DS1814 5-Volt MicroMonitor and the DS1819 3.3V MicroMonitor monitor three vital conditions for a microprocessor: power supply, software execution, and external override. First, a precision temperature-compensated reference and comparator circuit monitor the status of VCC. When an out-of-tolerance condition occurs, an internal power-fail signal is generated which forces the reset(s) to an active state. When VCC returns to an in-tolerance condition, the reset signal is kept in the active state for a minimum of 140ms to allow the power supply and processor to stabilize. The DS1814/DS1819 ‘A' and ‘C' perform pushbutton reset control. They debounce the pushbutton input and generate an active reset pulse width of 140ms minimum. The DS1814/9 'A' and 'B' versions perform a watchdog function. The watchdog is an internal timer that forces the reset signals to the active state if the strobe input does not change state every 1.12 seconds. The watchdog timer function can be disabled by leaving the watchdog strobe input disconnected.

Key Features Halts and restarts an out-of-control microprocessor Holds microprocessor in check during power transients Automatically restarts microprocessor after power failure Monitors pushbutton for external override Accurate 5%, 10%, or 20% (3V only) microprocessor power monitoring Eliminates the need for discrete components 20% tolerance for use with 3.0V systems Pin- and function-compatible with the MAX823/24/25 products Low cost SOT-23-5 package Industrial temperature range: -40°C to +85°C

DS1814, DS1819: Block Diagram

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