DS1836DS-20+ Analog Devices

DS1836/A/B/C/D 3.3V/5V MicroManager www.maxim-ic.com FEATURES PIN ASSIGNMENT 5V or 3.3V power-on reset RST(*RST) V 1 8 CC True 3V operation power switch 2 V 7 NMI BAT Switches to battery at 3.8V (2.6V for 3.3V versions) 3 6 NC IN Excellent for systems designed to operate 4 5 GND V OUT with dual power supplies 8-Pin DIP (300mil) Asserts resets during power transients Maintains reset for 350ms after V returns to CC RST(*RST) V 1 8 CC an in-tolerance condition 2 7 V NMI BAT Reduces need for discrete components NC 3 6 IN Precision temperature-compensated voltage 4 5 GND V OUT reference and voltage sensor 8-Pin SO (150mil) 8-pin DIP or space saving 8-pin SO surface mount available DS1836A/C (*DS1836B/D) CMOS reset output for low current operation Operating temperature of -40C to +85C PIN DESCRIPTION Perfect for PIC microprocessor applications V - Power Supply Input CC V - Battery Supply Input BAT NC - No Connect V - Power Supply Output OUT GND - Ground IN - Sense Input NMI - Non-maskable Interrupt RST (*RST) - Reset Output DESCRIPTION The DS1836 MicroManager performs three vital system functions. First, a precision temperature- compensated reference and comparator circuit monitor the status of the voltage on V and when an out- CC of-tolerance condition is detected, an internal power-fail signal is generated that forces the reset active. If V continues to degrade, it switches to the battery supply when V drops below 3.8V (2.6V for 3.3V CC CC versions). When V exceeds 3.9V (2.8V for 3.3V versions) V will again be supplied from V . CC OUT CC Reset will remain active for 350 ms after V returns to an in-tolerance condition. CC Lastly, the DS1836 supports a sense input that sends a non-maskable interrupt whenever the sense input drops below 1.25V. 1 of 9 121906 DS1836A/B/C/D OPERATION Power Monitor The DS1836 provides the functions of detecting out-of-tolerance conditions on a 3.3V or 5V power supply and warning a processor-based system of impending power failure. When V is detected as out of CC tolerance the RST will be forced active. When V returns to a valid state the RST will remain active for CC about 350ms and then return to an inactive state until the next V out-of-tolerance condition. CC On power-up reset is kept active for approximately 350ms after the power supply input has reached the selected tolerance. This allows the power supply and system power to stabilize before RST is released. Power Switch (DS1836A & B) The DS1836 switches the V output between V and V . On the initial power-up, V draws OUT CC BAT OUT current from the V input until V exceeds 3.9V. When V exceeds 3.9V V switches from V BAT CC CC OUT BAT to V and will not switch back to V until V drops below 3.8V. When V is below 3.8V, power CC BAT CC CC will be drawn from the supply with the highest voltage: either V or V . CC BAT Power Switch (DS1836C & D) The DS1836 switches the V output between V and V . On the initial power up, V draws OUT CC BAT OUT current from the V input until V exceeds 2.8V. When V exceeds 2.8V V switches from V BAT CC CC OUT BAT to V and will not switch back to V until V drops below 2.6V. When V is below 2.6V, power CC BAT CC CC will be drawn from the supply with the highest voltage either V or V . CC BAT BLOCK DIAGRAM Figure 1 * DS1836B and DS1836D 2 of 9