SGM803/809/810

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APPLICATION NOTES

BENEFITS OF AN ACCURATE RESET

THRESHOLD

In other microprocessor supervisory circuits, tolerances in

supply voltages lead to an overall increase in reset tolerance

levels due to the deterioration of the microprocessor reset

circuit’s power supply. The possibility of a malfunction during a

power failure is greatly reduced because the SGM803/

SGM809/SGM810 series can operate effectively even when

there are large degradations of the supply voltages. Another

advantage of the SGM803/ SGM809/SGM810 series is its very

accurate internal voltage reference circuit. These benefits

combine to produce an exceptionally reliable voltage monitor

circuit.

INTERFACING TO MICROPROCESSORS WITH

MULTIPLE INTERRUPTS

In a number of cases, it is necessary to interface many

interrupts from different devices (for example, thermal, altitude,

and velocity sensors). The SGM803/SGM809/SGM810 can

easily be integrated into existing interrupt-handling circuits, as

shown in Figure 1, or can be used as a standalone device.

SGM809

GND

RESET

OTHER SENSING

DEVICES

PRIORITY ENCODER

74LS147

4-LINE BCD TO

MICROPROCESSOR

Figure 1. Interfacing to Microprocessors with Multiple

Interrupts

INTERFACING TO OTHER DEVICES’ OUTPUT

The SGM803/SGM809/SGM810 series is designed to integrate

with as many devices as possible and, therefore, has a

be used in both 3 V and 5 V, or any nominal voltage within the

simplifies interfacing this device to other devices.

ENSURING A VALID RESET OUTPUT DOWN TO

longer sinks current. A high impedance CMOS logic input

levels. To eliminate this problem, a 100kΩ resistor should be

connected from RESET to ground.

SGM809

GND

RESET