Pin-Selectable Watchdog Timers

_______________________________________________________________________________________

5

PIN

NAME

FUNCTION

1

WDI

triggers a pulse. The internal watchdog timer clears whenever a WDO is asserted or whenever WDI sees a

rising or falling edge.

2

GND

Ground

3

N.C.

Not Connected. Do not make any connection to this pin.

4

SET0

Set Zero. Logic input for selecting startup delay and watchdog timeout periods. See Table 1 for timing details.

5

SET1

Set One. Logic input for selecting startup delay and watchdog timeout periods. See Table 1 for timing details.

6

SET2

Set Two. Logic input for selecting startup delay and watchdog timeout periods. See Table 1 for timing details.

7

WDO

out. The MAX6369/MAX6371/MAX6373 have open-drain outputs and require a pull-up resistor. The

MAX6370/MAX6372/MAX6374 outputs are push-pull.

Supply Voltage (+2.5V to +5.5V)

Table 1. Minimum Timeout Settings

Pin Description

Detailed Description

The MAX6369–MAX6374 are flexible watchdog circuits

for monitoring µP activity. During normal operation, the

internal timer is cleared each time the µP toggles the

WDI with a valid logic transition (low to high or high to

remains high as long as the input is strobed within the

selected timeout period. If the input is not strobed

before the timeout period expires, the watchdog output

is asserted low for the watchdog output pulse width

control pins (SET0, SET1, and SET2) determine watch-

dog timing characteristics. The three basic timing varia-

tions for the watchdog startup delay and the normal

watchdog timeout period are summarized below (see

Table 1 for the timeout characteristics for all devices in

the family):

• Watchdog Startup Delay:

Provides an initial delay before the watchdog timer is

started.

Allows time for the µP system to power up and initial-

ize before assuming responsibility for normal watch-

dog timer updates.

Includes several fixed or pin-selectable startup delay

options from 200µs to 60s, and an option to wait for

the first watchdog input transition before starting the

watchdog timer.

LOGIC INPUTS

MAX6369/MAX6370

MAX6371/MAX6372

MAX6373/MAX6374

SET2

SET1

SET0

0

0

0

1ms

1ms

3ms

3ms

0

0

1

10ms

3ms

3s

3s

0

1

0

30ms

10ms

60s

1s

0

1

1

Disabled

Disabled

Disabled

Disabled

1

0

0

100ms

100ms

200

µs30µs

1

0

1

1s

300ms

First Edge

1s

1

1

0

10s

3s

First Edge

10s

1

1

1

60s

60s

60s

10s