ADM809LART Просмотр технического описания (PDF) - Analog Devices
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ADM809LART Datasheet PDF : 6 Pages
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ADM809/ADM810
INTERFACING TO OTHER DEVICES OUTPUT
The ADM809/ADM810 Series is designed to integrate with as
many devices as possible and therefore has a standard output
dependant on VCC. This enables the part to be used in both 3 V
and 5 V or any nominal voltage within the minimum and maxi-
mum 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, 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
THE BENEFITS OF A VERY ACCURATE RESET
THRESHOLD
In other microprocessor supervisory circuits, tolerances in sup-
ply 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 ADM809 and
ADM810 series can operate effectively even when there are
large degradations of the supply voltages. Another advantage of
the ADM809 and ADM810 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 (i.e., thermal, attitude and velocity sen-
sors). The ADM809 and ADM810 can easily be integrated into
existing interrupt-handling circuits (Figure 11) or used as a
stand-alone device.
PRIORITY ENCODER
74LS147
VCC
4 LINE BCD
TO µP
GND
Figure 10. Ensuring a Valid RESET Output Down to
VCC = 0 V
VCC
ADM809
RESET
GND
OTHER SENSING
DEVICES
Figure 11. Interfacing to µPs with Multiple Interrupts
REV. 0
–5–
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