DS1810R-5+T&R Analog Devices

DS1810 5V EconoReset with Push-Pull Output www.maxim-ic.com FEATURES PIN ASSIGNMENT Automatically restarts a microprocessor after 3 power failure DALLAS DS1810 Maintains reset for 150 ms after V returns CC Econo Reset to an in-tolerance condition Reduces need for discrete components Precision temperature-compensated voltage 12 reference and voltage sensor TOP VIEW SOT-23 PACKAGE Low-cost TO-92 or space saving surface See Mech. mount SOT-23 packages available Drawings Section 1 2 3 On Website Push-Pull output for low current operation Operating temperature -40C to +85C 1 2 3 BOTTOM VIEW TO-92 PACKAGE See Mech. Drawings Section On Website PIN DESCRIPTION TO-92 1 RST Active Low Reset Output 2 V Power Supply CC 3 GND Ground SOT-23 1 RST Active Low Reset Output 2 V Power Supply CC 3 GND Ground DESCRIPTION The DS1810 EconoReset uses a precision temperature reference and comparator circuit to monitor the status of the power supply (V ). When an out-of-tolerance condition is detected, an internal power-fail CC signal is generated which forces reset to the active state. When V returns to an in-tolerance condition, CC the reset signal is kept in the active state for approximately 150 ms to allow the power supply and processor to stabilize. 1 of 5 041002DS1810 OPERATION - POWER MONITOR The DS1810 provides the function of detecting out-of-tolerance power supply conditions and warning a processor-based system of impending power failure. When V is detected as out-of-tolerance, the RST CC signal is asserted. On power-up, RST is kept active for approximately 150 ms after the power supply has reached the selected tolerance. This allows the power supply and microprocessor to stabilize before RST is released. BLOCK DIAGRAM (PUSH-PULL OUTPUT) Figure 1 APPLICATION EXAMPLE Figure 2 OUTPUT VALID CONDITIONS All versions of the DS1810 can maintain a valid output as long as V remains above 1.2 volt. However, CC the RST outputs on the DS1810 use a push-pull structure which can maintain a valid output below 1.2 volts on an input. To sink current below 1.2 volts, a resistor can be connected from RST to Ground (see Figure 3). This arrangement will maintain a valid value on the RST outputs even it V approaches 0 CC volts. During both power-up and -down this arrangement will draw current when RST is in the high state. A value of about 100 k should be adequate to maintain a valid condition. 2 of 5