DS1819 Datasheet | Dallas Semiconductor

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 ponents 20% tolerance for use with 3.0V systems Pin- and function-patible with the MAX823/24/25 products Low cost SOT-23-5 package Industrial temperature range: -40°C to +85°C PIN ASSIGNMENT 3 2 1 SOT-23-5 PACKAGE See Mech. Drawing PIN DESCRIPTION DS181x A 1 RST 2 GND PBRST 3 4 ST 5 VCC DS181x B 1 RST 2 GND 3 RST 4 ST 5 VCC DS181x C 1 RST 2 GND 3 RST 4 PBRST 5 VCC Active Low Reset Output Ground Pushbutton Reset Input Strobe Input Power Supply DEVICE PBRST WD X X DS181x A X DS181x B X X DS181x C X X x = "DS1814" for 5V devices x = "DS1819" for 3V devices Active Low Reset Output Ground Active High Reset Output Strobe Input Power Supply Active Low Reset Output Ground Active High Reset Output Pushbutton Reset Input Power Supply DESCRIPTION The DS1814 5-Volt Micro Monitor and the DS1819 3.3V Micro Monitor monitor three vital conditions for a microprocessor: power supply, software execution, and external override. First, a precision temperaturepensated reference and parator 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. 1 of 8 122001 DS1814/DS1819 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...