DS1834+ Analog Devices

DS1834/A/D Dual EconoReset with Pushbutton www.dalsemi.com FEATURES PIN ASSIGNMENT 5V power-on reset 3.3V IN 5V 1 8 IN 3.3V power-on reset 2 5V RST 7 3.3V RST Internal power is drawn from higher of either the 5V input or the 3.3V input 3 6 IN IN 5V TOL 3.3V TOL Excellent for systems designed to operate 4 5 PBRST GND with dual power supplies DS1834 8-Pin DIP (300-mil) Asserts resets during power transients Pushbutton reset input for system override 3.3V 5V 1 8 IN IN Maintains reset for 350 ms after V returns CC 5V RST 2 7 3.3V RST to an in-tolerance condition 5V TOL 3 6 3.3V TOL Reduces need for discrete components PBRST GND 4 5 Precision temperature-compensated voltage DS1834 8-Pin SOIC (150-mil) reference and voltage sensor 8-pin DIP, 8-pin SOIC, and 8-pin -SOP 5V 3.3V IN 1 8 IN available 5V RST (*RST) 2 7 3.3V RST (*RST) 5V TOL 3 6 3.3V TOL CMOS output for low current operation on GND 4 5 PBRST the DS1834 and DS1834D DS1834 8-Pin -SOP (118-mil) Operating temperature of -40C to +85C PIN DESCRIPTION 5V - 5V Power Supply Input IN 5V RST (*RST) - 5V Reset Output 5V TOL - Selects 5V Input Tolerance GND - Ground PBRST - Pushbutton Reset 3.3V TOL - Selects 3.3V Input Tolerance 3.3V RST (*RST) - 3.3V Reset Output 3.3V - 3.3V Power Supply Input IN *DS1834D Active High Reset DESCRIPTION The DS1834 Dual EconoResets monitors three vital system conditions: 5-volt supply, 3.3-volt supply, and an external override. First a precision temperature reference and comparator circuit monitor the status of the 5-volt supply and the 3.3-volt supply. When an out-of-tolerance condition is detected, an internal power-fail signal is generated which forces the reset of the affected supply to an active state. Lastly, the DS1834 supports an external reset via an internally debounced pushbutton input. When the pushbutton is pulled low both resets will be asserted for approximately 350 ms after the pushbutton is released. 1 of 7 071700DS1834/A/D OPERATION Power Monitor The DS1834 provides the functions of detecting out-of-tolerance conditions on a 3.3-volt and 5-volt power supply and warning a processor-based system of impending power failure. When an input is detected as out of tolerance on either voltage input the RST for that supply will be forced active. When that input returns to a valid state the RST will remain active for about 350 ms and then return to an inactive state until the next input out-of-tolerance condition. On power-up both resets are kept active for approximately 350 ms after the power supply inputs have reached the selected tolerance. This allows the power supply and system power to stabilize before RST is released. All internal operating current for the DS1834 will be drawn from the input with the highest voltage level. The outputs will draw current only from the controlling input (5V IN or 3.3V IN). DS1834 BLOCK DIAGRAM Figure 1 DS1834A BLOCK DIAGRAM OUTPUT Figure 2 2 of 7