MAX6369 Maxim, MAX6369 Datasheet - Page 5

• Manufacturer Part Number: MAX6369
• Description: Pin-Selectable Watchdog Timers
• Manufacturer: Maxim

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
low) within the selected timeout period (t
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
(t
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
Table 1. Minimum Timeout Settings
WDO
PIN
SET2
1
2
3
4
5
6
7
8
0
0
0
0
1
1
1
1
). The device type and the state of the three logic
LOGIC INPUTS
NAME
SET0
SET1
SET2
WDO
GND
N.C.
WDI
V
CC
SET1
0
0
1
1
0
0
1
1
Watchdog Input. If WDI remains either high or low for the duration of the watchdog timeout period (t
triggers a pulse. The internal watchdog timer clears whenever a WDO is asserted or whenever WDI sees a
rising or falling edge.
Ground
Not Connected. Do not make any connection to this pin.
S et Z er o. Log i c i np ut for sel ecti ng star tup d el ay and w atchd og ti m eout p er i od s. S ee Tab l e 1 for ti m i ng d etai l s.
S et One. Log i c i np ut for sel ecti ng star tup d el ay and w atchd og ti m eout p er i od s. S ee Tab l e 1 for ti m i ng d etai l s.
S et Tw o. Log i c i np ut for sel ecti ng star tup d el ay and w atchd og ti m eout p er i od s. S ee Tab l e 1 for ti m i ng d etai l s.
Watchdog Output. Pulses low for the watchdog output pulse width, t
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)
_______________________________________________________________________________________
SET0
Detailed Description
0
1
0
1
0
1
0
1
MAX6369/MAX6370
t
DELAY
Disabled
100ms
Pin-Selectable Watchdog Timers
10ms
30ms
1ms
10s
60s
1s
WD
, t
WD
). The WDO
MAX6371/MAX6372
t
DELAY
Disabled
100ms
300ms
watchdog timeout period are summarized below (see
Table 1 for the timeout characteristics for all devices in
the family):
• Watchdog Startup Delay:
10ms
1ms
3ms
FUNCTION
60s
= 60s, t
3s
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.
WD
WDO
, when the internal watchdog times
First Edge
First Edge
Disabled
t
200µs
DELAY
3ms
60s
60s
3s
MAX6373/MAX6374
Pin Description
Disabled
WD
30µs
3ms
t
10s
10s
WD
3s
1s
1s
), WDO
5