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SP802MCP Datasheet(PDF) 9 Page - Sipex Corporation |
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SP802MCP Datasheet(HTML) 9 Page - Sipex Corporation |
9 / 16 page SP690A/692ADS/08 SP690A/692A Low Power Microprocessor Supervisory with Battery Switch-Over © Copyright 2000 Sipex Corporation 9 THEORY OF OPERATION The SP690A/692A/802L/802M/805L/805M microprocessor ( µP) supervisory circuits monitor the power supplied to digital circuits such as microprocessors, microcontrollers, or memory. The series is an ideal solution for portable, battery-powered equipment that requires power supply monitoring. Implementing this series will reduce the number of components and overall complexity. The watchdog functions of this product family will continuously oversee the operational status of a system. The operational features and benefits of the SP690A/692A/802L/802M/805L/805M are described in more detail below. Reset Output The microprocessor's ( µP's) reset input starts the µP in a known state. When the µP is in an unknown state, it should be held in reset. The SP690A/SP692A/SP802 assert reset during power-up and prevent code execution errors during power-down or brownout conditions. On power-up, once V CC reaches 1V, RESET is guaranteed to be a logic low. As V CC rises, RESET remains low. When V CC exceeds the reset threshold, RESET will remain low for 200ms, Figure 9. If a brownout condition occurs and V CC dips below the reset threshold, RESET is triggered. Each time RESET is triggered, it stays low for the reset pulse width interval. If a brownout condition interrupts a previously initiated reset pulse, the reset pulse continues for another 200ms. On power-down, once V CC goes below the threshold, RESET is guaranteed to be logic low until V CC drops below 1V. RESET is also triggered by a watchdog timeout. If WDI remains either high or low for a period that exceeds the watchdog timeout period (1.6 sec), RESET pulses low for 200mS. As long as RESET is asserted, the watchdog timer remains clear. When RESET comes high, the watchdog resumes timing and must be serviced within 1.6sec. If WDI is tied high or low, a RESET pulse is triggered every 1.8sec (t WD plus tRS). FEATURES The SP690A/692A/802L/802M/805L/805M provide four key functions: 1. A battery backup switching for CMOS RAM, CMOS microprocessors, or other logic. 2. A reset output during power-up, power-down and brownout conditions. 3. A reset pulse if the optional watchdog timer has not been toggled within a specified time. 4. A 1.25V threshold detector for power-fail warning, low battery detection, or to monitor a power supply other than +5V. The parts differ in their reset-voltage threshold levels and reset outputs. The SP690A/802L/ 805L generate a reset when the supply voltage drops below 4.65V. The SP692A/802M/805M generate a reset below 4.40V. The SP690A/692A/802L/802M/805L/805M are ideally suited for applications in automotive systems, intelligent instruments, and battery- powered computers and controllers. All designs into an environment where it is critical to monitor the power supply to the µP and it’s related digital components will find the SSP690A/692A/802L/802M/805L/805M ideal. Figure 12. Typical Operating Circuit GND GND RESET NMI I/O LINE VCC RESET PFO WDI VOUT BUS VCC GND VBATT R2 R1 Unregulated Regulated +5V VCC 0.1 µF PFI DC Lithium Battery 3.6V µP CMOS RAM |
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