ADM706P/R/S/T, ADM708R/S/T
Microprocessor activity is monitored using the WDI input. This
is driven using an output line from the processor. The software
routines should toggle this line at least once every 1.6 seconds.
If a problem occurs and this line is not toggled, then WDO goes
low and a nonmaskable interrupt is generated. This interrupt
routine may be used to clear the problem.
If, in the event of inactivity on the WDI line, a system reset is
required, then the
WDO
output should be connected to the
input as shown in Figure 16.
RESET
RESET
V
X
+3V/+3.3V
V
CC
R1
RESET
WDI
RESET
ADM706
PFI
MR
GND
PFO
P
Figure 17. Monitoring 3 V/3.3 V and an Additional
Supply, V
X
P
ADM706
PFI
MR
WDI
WDO
GND
I/O LINE
Ps with Bidirectional
RESET
Figure 16.
RESET
from WDO
Monitoring Additional Supply Levels
In order to prevent contention for microprocessors with a bidi-
rectional reset line, a current limiting resistor should be inserted
between the ADM70x
RESET
output pin and the
µP
reset pin.
This will limit the current to a safe level if there are conflicting
output reset levels. A suitable resistor value is 4.7 kΩ. If the re-
set output is required for other uses, then it should be buffered
as shown in Figure 18.
+3V/+3.3V
BUFFERED
RESET
It is possible to use the power-fail comparator to monitor a
second supply as shown in Figure 17. The two sensing resistors
R1 and R2 are selected such that the voltage on PFI drops below
1.25 V at the minimum acceptable input supply. The
PFO
output
may be connected to the
MR
input so that a RESET is gener-
ated when the supply drops out of tolerance. In this case if
either supply drops out of tolerance, a RESET will be generated.
V
CC
ADM70x
RESET
GND
RESET
P
GND
Figure 18. Bidirectional I-O RESET
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Plastic DIP
(N-8)
0.430 (10.92)
0.348 (8.84)
8
5
8-Lead SOIC
(SO-8)
0.1968 (5.00)
0.1890 (4.80)
0.280 (7.11)
0.240 (6.10)
0.325 (8.25)
0.300 (7.62)
0.060 (1.52)
0.015 (0.38)
0.130
(3.30)
MIN
0.015 (0.381)
0.008 (0.204)
0.195 (4.95)
0.115 (2.93)
8
5
4
1
4
0.1574 (4.00)
0.1497 (3.80)
PIN 1
1
0.2440 (6.20)
0.2284 (5.80)
PIN 1
0.100 (2.54)
BSC
0.160 (4.06)
0.115 (2.93)
SEATING
PLANE
0.0192 (0.49)
0.0138 (0.35)
8
0.0098 (0.25) 0
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
0.022 (0.558) 0.070 (1.77) SEATING
0.014 (0.356) 0.045 (1.15) PLANE
–8–
REV. A
PRINTED IN U.S.A.
0.210
(5.33)
MAX
0.0500 (1.27)
BSC
0.0098 (0.25)
0.0040 (0.10)
0.0688 (1.75)
0.0532 (1.35)
0.0196 (0.50)
0.0099 (0.25)
45
C1998a–0–12/99
R2
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