Containing Lead (Pb).......................................................+240°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
CC
= +2.5V to +5.5V, SET_ = V
CC
or GND, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C and
V
CC
= +3V.) (Note 1)
PARAMETER
Operating Voltage Range
Supply Current
Input High Voltage
SYMBOL
V
CC
I
CC
V
IH
No load
T
A
= -40°C to +85°C
T
A
= -40°C to +125°C
WDI, SET0, SET1, SET2
V
CC
≥
3.3V,
T
A
= -40°C to +85°C
WDI, SET0,
SET1, SET2
V
CC
≥
3.3V,
T
A
= -40°C to +125°C
V
CC
≥
2.5V,
T
A
= -40°C to +85°C
V
CC
≥
2.5V,
T
A
= -40°C to +125°C
Logic Input Current (Note 2)
WDO
Output Low
Voltage
V
WDI
or V
SET_
= 0V or V
CC
I
SINK
= 1.2mA, V
CC
> 2.7V, watchdog
output asserted
V
OL
I
SINK
= 6mA, V
CC
> 4.5V, watchdog
output asserted
V
WDO
= 0 to +5.5V, output deasserted,
MAX6369/MAX6371/MAX6373
I
SOURCE
= 500µA, V
CC
> 2.7V, watchdog
output deasserted
V
OH
I
SOURCE
= 800µA, V
CC
> 4.5V, watchdog
output deasserted
0.8
×
V
CC
V
V
CC
- 1.5
0
0.8
×
V
CC
0.8
0.6
V
0.6
0.4
±10
0.3
0.4
1
nA
V
V
µA
CONDITIONS
MIN
2.5
8
10
TYP
MAX
5.5
20
µA
22
V
UNITS
V
Input Low Voltage
V
IL
WDO
Leakage Current
I
LKG
WDO
Output High
Voltage
2
Maxim Integrated
MAX6369–MAX6374
Pin-Selectable Watchdog Timers
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +2.5V to +5.5V, SET_ = V
CC
or GND, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C and
V
CC
= +3V.) (Note 1)
PARAMETER
MAX6369/MAX6370
V
SET2
= 0V, V
SET1
= 0V, V
SET0
= 0V
V
SET2
= 0V, V
SET1
= 0,V SET0 = V
CC
V
SET2
= 0V, SET1 = V
CC
, V
SET0
= 0V
Startup Delay Period
t
DELAY
V
SET2
= 0V, SET1 = V
CC
, SET0 = V
CC
SET2 = V
CC
, V
SET1
= 0V, V
SET0
= 0V
SET2 = V
CC
, V
SET1
= 0V, SET0 = V
CC
SET2 = V
CC
, SET1 = V
CC
, V
SET0
= 0V
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
V
SET2
= 0V, V
SET1
= 0V, V
SET0
= 0V
V
SET2
= 0V, V
SET1
= 0V, SET0 = V
CC
V
SET2
= 0V, SET1 = V
CC
, V
SET0
= 0V
Watchdog Timeout
Period
t
WD
V
SET2
= 0V, SET1 = V
CC
, SET0 = V
CC
SET2 = V
CC
, V
SET1
= 0V, V
SET0
= 0V
SET2 = V
CC
, V
SET1
= 0V, SET0 = V
CC
SET2 = V
CC
, SET1 = V
CC
, V
SET0
= 0V
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
MAX6371/MAX6372
Startup Delay Period
t
DELAY
V
SET2
= 0V, SET1 = V
CC
, SET0 = V
CC
All other SET_ conditions
V
SET2
= 0V, V
SET1
= 0V, V
SET0
= 0V
V
SET2
= 0V, V
SET1
= 0V, SET0 = V
CC
V
SET2
= 0V, SET1 = V
CC
, V
SET0
= 0V
Watchdog Time-Out
Period
t
WD
V
SET2
= 0V, SET1 = V
CC
, SET0 = V
CC
SET2 = V
CC
, V
SET1
= 0V, V
SET0
= 0V
SET2 = V
CC
, V
SET1
= 0V, SET0 = V
CC
SET2 = V
CC
, SET1 = V
CC
, V
SET0
= 0V
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
MAX6373/MAX6374
V
SET2
= 0V, V
SET1
= 0V, V
SET0
= 0V
V
SET2
= 0V, V
SET1
= 0V, SET0 = V
CC
V
SET2
= 0V, SET1 = V
CC
, V
SET0
= 0V
Startup Delay Period
t
DELAY
SET2 = 0V, SET1 = V
CC
, SET0 = V
CC
SET2 = V
CC
, V
SET1
= 0V, V
SET0
= 0V
SET2 = V
CC
, V
SET1
= 0V, SET0 = V
CC
SET2 = V
CC
, SET1 = V
CC
, V
SET0
= 0V
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
3
3
60
200
Watchdog Disabled
600
µs
First Edge (Note 3)
First Edge (Note 3)
60
180
s
9
9
180
ms
s
Watchdog Disabled
60
1
3
10
100
300
3
60
Watchdog Disabled
300
900
9
180
ms
s
180
3
9
30
ms
s
1
10
30
100
1
10
60
1
10
30
100
1
10
60
3
30
90
300
3
30
180
3
30
90
300
3
30
180
s
ms
ms
s
ms
ms
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Watchdog Disabled
Watchdog Disabled
Maxim Integrated
3
MAX6369–MAX6374
Pin-Selectable Watchdog Timers
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +2.5V to +5.5V, SET_ = V
CC
or GND, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at T
A
= +25°C and
V
CC
= +3V.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
V
SET2
= 0V, V
SET1
= 0V, V
SET0
= 0V
V
SET2
= 0V, V
SET1
= 0V, SET0 = V
CC
V
SET2
= 0V, SET1 = V
CC
, V
SET0
= 0V
Watchdog Timeout
Period
t
WD
V
SET2
= 0V, SET1 = V
CC
, SET0 = V
CC
SET2 = V
CC
, V
SET1
= 0V, V
SET0
= 0V
SET2 = V
CC
, V
SET1
= 0V, SET0 = V
CC
SET2 = V
CC
, SET1 = V
CC
, V
SET0
= 0V
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
Watchdog Input Pulse Width
(Note 2)
Watchdog Output Pulse Width
Internal Setup Time
(Note 4)
t
WDI
t
WDO
t
SETUP
After
WDO
deasserted
MAX6369/MAX6371/MAX6373
MAX6370/MAX6372/MAX6374
After
WDO
deasserted
MIN
3
3
1
Watchdog Disabled
30
1
10
10
100
100
1
100
300
3
300
90
3
30
30
ns
ms
ms
ms
s
µs
TYP
MAX
9
9
3
UNITS
ms
s
Note 1:
Production tested at T
A
= +25°C. Guaranteed by design over temperature limits.
Note 2:
Guaranteed by design.
Note 3:
In this setting the watchdog timer is inactive and startup delay ends when WDI sees its first level transition. See the
Selecting
Device Timing
section for more information.
Note 4:
After power-up, or a setting change, there is an internal setup time during which WDI is ignored.
Typical Operating Characteristics
(Circuit of Figure 1, T
A
= +25°C, unless otherwise noted
.)
SUPPLY CURRENT
vs. TEMPERATURE
MAX6369/74-01
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
NORMALIZED WATCHDOG TIMEOUT PERIOD
MAX6369/74-02
14
1.003
1.002
1.001
1.000
0.999
0.998
0.997
12
SUPPLY CURRENT (μA)
V
CC
= +5.5V
10
8
V
CC
= +2.5V
6
4
-40
-15
10
35
60
85
TEMPERATURE (°C)
-40
-15
10
35
60
85
TEMPERATURE (°C)
4
Maxim Integrated
MAX6369–MAX6374
Pin-Selectable Watchdog Timers
Pin Description
PIN
1
2
3
4
5
6
7
8
NAME
WDI
GND
N.C.
SET0
SET1
SET2
WDO
V
CC
FUNCTION
Watchdog Input. If WDI remains either high or low for the duration of the watchdog timeout period (t
WD
),
WDO
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.
Set Zero. Logic input for selecting startup delay and watchdog timeout periods. See Table 1 for timing details.
Set One. Logic input for selecting startup delay and watchdog timeout periods. See Table 1 for timing details.
Set Two. Logic input for selecting startup delay and watchdog timeout periods. See Table 1 for timing details.
Watchdog Output. Pulses low for the watchdog output pulse width, t
WDO
, when the internal watchdog times
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
LOGIC INPUTS
SET2
0
0
0
0
1
1
1
1
SET1
0
0
1
1
0
0
1
1
SET0
0
1
0
1
0
1
0
1
MAX6369/MAX6370
t
DELAY
, t
WD
1ms
10ms
30ms
Disabled
100ms
1s
10s
60s
MAX6371/MAX6372
t
DELAY
= 60s, t
WD
1ms
3ms
10ms
Disabled
100ms
300ms
3s
60s
MAX6373/MAX6374
t
DELAY
3ms
3s
60s
Disabled
200μs
First Edge
First Edge
60s
t
WD
3ms
3s
1s
Disabled
30μs
1s
10s
10s
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
low) within the selected timeout period (t
WD
). The
WDO
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
WDO
). The device type and the state of the three logic
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
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