ADM803MAKS-REEL データシートの表示（PDF） - Analog Devices

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ADM803MAKS-REEL

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

Analog Devices 

400

350

300

250

200

ADM8_L/M/J

150

100

ADM8_R/S/T/Z

50

0

1

10

100

1000

RESET COMPARATOR OVERDRIVE, VTH – VCC (mV)

TPC 7. Maximum Transient Duration without Causing a

Reset Pulse vs. Reset Comparator Overdrive

ADM803/ADM809/ADM810

Benefits of a Very 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 ADM803/ADM809/ADM810 series

can operate effectively even when there are large degradations

of the supply voltages. Another advantage of the ADM803/

ADM809/ADM810 series is its very accurate internal voltage

reference circuit. These benefits combine to produce an excep-

tionally 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 (e.g., thermal, altitude, and velocity sensors).

The ADM803/ADM809/ADM810 can easily be integrated into

existing interrupt-handling circuits (Figure 4) or be used as a

standalone device.

INTERFACING TO OTHER DEVICES’ OUTPUT

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 part to be used in

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

and maximum specifications for VCC. Because of this design

approach, interfacing this device to other devices is simplified.

Ensuring a Valid Reset Output Down to VCC = 0 V

When VCC falls below 0.8 V, the ADM803/ADM809’s 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

PRIORITY ENCODER

74LS147

VCC

4-LINE BCD TO

MICROPROCESSOR

VCC

ADM809

RESET

OTHER SENSING

DEVICES

GND

Figure 4. Interfacing to Microprocessors with

Multiple Interrupts

GND

Figure 3. Ensuring a Valid Reset Output Down

to VCC = 0 V

REV. C

–7–

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