REV. A

–8–

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.

ADM706

RESET

GND

I/O LINE

P

MR

PFI

WDI

WDO

RESET

Figure 16.

RESET from WDO

Monitoring Additional Supply Levels

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.

ADM706

RESET

GND

P

MR

PFI

WDI

PFO

RESET

R1

R2

+3V/+3.3V

Figure 17. Monitoring 3 V/3.3 V and an Additional

Ps with Bidirectional

RESET

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 k

Ω. If the re-

set output is required for other uses, then it should be buffered

as shown in Figure 18.

ADM70x

RESET

GND

P

RESET

GND

BUFFERED

RESET

+3V/+3.3V

Figure 18. Bidirectional I-O RESET

OUTLINE DIMENSIONS

Dimensions shown in inches and (mm).

8-Lead SOIC

(SO-8)

8-Lead Plastic DIP

(N-8)

SEATING

PLANE

0.060 (1.52)

0.015 (0.38)

0.210

(5.33)

MAX

0.022 (0.558)

0.014 (0.356)

0.160 (4.06)

0.115 (2.93)

0.070 (1.77)

0.045 (1.15)

0.130

(3.30)

MIN

8

14

5

PIN 1

0.280 (7.11)

0.240 (6.10)

0.100 (2.54)

BSC

0.430 (10.92)

0.348 (8.84)

0.195 (4.95)

0.115 (2.93)

0.015 (0.381)

0.008 (0.204)

0.325 (8.25)

0.300 (7.62)

0.0098 (0.25)

0.0075 (0.19)

0.0500 (1.27)

0.0160 (0.41)

8

0

0.0196 (0.50)

0.0099 (0.25)

45

85

4

1

0.1968 (5.00)

0.1890 (4.80)

0.2440 (6.20)

0.2284 (5.80)

PIN 1

0.1574 (4.00)

0.1497 (3.80)

0.0500 (1.27)

BSC

0.0688 (1.75)

0.0532 (1.35)

SEATING

PLANE

0.0098 (0.25)

0.0040 (0.10)

0.0192 (0.49)

0.0138 (0.35)