ADM803/ADM809/ADM810 Data Sheet
Rev. I | Page 8 of 11
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 V
CC
. 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 V
CC
. This design simplifies
interfacing the ADM803/ADM809/ADM810 to other devices.
ENSURING A VALID RESET OUTPUT DOWN TO
V
CC
= 0 V
When V
CC
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.
Figure 12. Ensuring a Valid Reset Output Down to V
CC
= 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.
Figure 13. Interfacing to Microprocessors with Multiple Interrupts
GND
ADM809
V
CC
CC
RESET
03736-011
4-LINE BCD TO
MICROPROCESSOR
ADM809
GND
V
CC
V
CC
RESET
OTHER SENSING
DEVICES
PRIORITY ENCODER
74LS147
03736-012
