ADM809RAKS-REEL データシートの表示（PDF） - Analog Devices

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ADM809RAKS-REEL

Microprocessor Supervisory Circuits in 3-Lead SC70 and SOT-23

Analog Devices 

ADM803/ADM809/ADM810

INTERFACING TO OTHER DEVICES

The ADM803/ADM809/ADM810 series is designed to integrate

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

output dependent on VCC. This enables the parts to be used in

both 3 V and 5 V, or any nominal voltage within the minimum

and maximum specifications for VCC. This design simplifies

interfacing the ADM803/ADM809/ADM810 to other devices.

ENSURING A VALID RESET OUTPUT DOWN TO

VCC = 0 V

When VCC falls below 0.8 V, the ADM803/ADM809 RESET no

longer sinks current. A high impedance CMOS logic input

connected to RESET may, therefore, drift to undetermined logic

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

connected from RESET to ground.

VCC

VCC

ADM809

RESET

GND

Figure 12. Ensuring a Valid Reset Output Down to VCC = 0 V

BENEFITS OF AN ACCURATE RESET THRESHOLD

In other microprocessors, tolerances in supply voltages lead

to an overall increase in reset tolerance levels due to the

deterioration of the reset circuit’s power supply. In the

ADM803/ADM809/ADM810, the possibility of a malfunction

during a power failure is greatly reduced because the devices

can operate effectively even when there are large degradations

of the supply voltages. Another advantage is the very accurate

internal voltage reference circuit of the ADM803/ADM809/

ADM810. 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 ADM803/ADM809/ADM810 can easily

be integrated into existing interrupt-handling circuits, as shown

in Figure 13, or can be used as standalone devices.

PRIORITY ENCODER

74LS147

4-LINE BCD TO

MICROPROCESSOR

VCC

VCC

ADM809

RESET

OTHER SENSING

DEVICES

GND

Figure 13. Interfacing to Microprocessors with Multiple Interrupts

Rev. H | Page 8 of 12

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