General Description
The MAX6369MAX6374 are pin-selectable watchdog
timers that supervise microprocessor (P) activity and
signal when a system is operating improperly. During
normal operation, the microprocessor should repeated-
ly toggle the watchdog input (WDI) before the selected
watchdog timeout period elapses to demonstrate that
the system is processing code properly. If the P does
not provide a valid watchdog input transition before the
timeout period expires, the supervisor asserts a watch-
dog (WDO) output to signal that the system is not exe-
cuting the desired instructions within the expected time
frame. The watchdog output pulse can be used to reset
the P or interrupt the system to warn of processing
errors.
The MAX6369MAX6374 are flexible watchdog timer
supervisors that can increase system reliability through
notification of code execution errors. The family offers
several pin-selectable watchdog timing options to
match a wide range of system timing applications:
Watchdog startup delay: provides an initial delay
before the watchdog timer is started.
Watchdog timeout period: normal operating watch-
dog timeout period after the initial startup delay.
Watchdog output/timing options: open drain (100ms)
or push-pull (1ms).
The MAX6369MAX6374 operate over a +2.5V to +5.5V
supply range and are available in miniature 8-pin
SOT23 packages.
________________________Applications
Embedded Control Systems
Industrial Controllers
Critical P and Microcontroller (C) Monitoring
Automotive
Telecommunications
Networking
Features
o Precision Watchdog Timer for Critical
P Applications
o Pin-Selectable Watchdog Timeout Periods
o Pin-Selectable Watchdog Startup Delay Periods
o Ability to Change Watchdog Timing Characteristics
Without Power Cycling
o Open-Drain or Push-Pull Pulsed Active-Low
Watchdog Output
o Watchdog Timer Disable Feature
o +2.5V to +5.5V Operating Voltage
o 8A Low Supply Current
o No External Components Required
o Miniature 8-Pin SOT23 Package
MAX6369MAX6374
Pin-Selectable Watchdog Timers
________________________________________________________________ Maxim Integrated Products
1
PART
TEMP
RANGE
PIN-
PACKAGE
TOP
MARKS
MAX6369KA-T
-40
C to +85C
8 SOT23-8
AADC
MAX6370KA-T
-40
C to +85C
8 SOT23-8
AADD
MAX6371KA-T
-40
C to +85C
8 SOT23-8
AADE
MAX6372KA-T
-40
C to +85C
8 SOT23-8
AADF
MAX6373KA-T
-40
C to +85C
8 SOT23-8
AADG
MAX6374KA-T
-40
C to +85C
8 SOT23-8
AADH
19-1676; Rev 2; 2/03
Ordering Information
PART
OUTPUT
WDO PULSE
WIDTH (ms)
MINIMUM STARTUP DELAY
MINIMUM WATCHDOG TIMEOUT
MAX6369
Open Drain
100
Selectable: 1ms to 60s
S el ectab l e: 1ms to 60s
MAX6370
Push-Pull
1
Selectable: 1ms to 60s
S el ectab l e: 1ms to 60s
MAX6371
Open Drain
100
60s
S el ectab l e: 1ms to 60s
MAX6372
Push-Pull
1
60s
S el ectab l e: 1ms to 60s
MAX6373
Open Drain
100
S el ectab l e: 200s to 60s or fi r st ed g e
S el ectab l e: 30s to 10s
MAX6374
Push-Pull
1
S el ectab l e: 200s to 60s or fi r st ed g e
S el ectab l e: 30s to 10s
Pin Configuration appears at end of data sheet.
Note: All devices are available in tape-and-reel only. Required
order increment is 2,500 pieces.
Selector Guide
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
MAX6369MAX6374
Pin-Selectable Watchdog Timers
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
CC
= +2.5V to +5.5V, SET_ = V
CC
or GND, T
A
= -40C to +85C, unless otherwise noted. Typical values are at T
A
= +25C and
V
CC
= +3V.) (Note 1)
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.
Terminal Voltage (with respect to GND)
V
CC
.....................................................................-0.3V to +6V
WDI.....................................................................-0.3V to +6V
WDO (Open Drain: MAX6369/71/73) .................-0.3V to +6V
WDO (Push-Pull: MAX6370/72/74 .......-0.3V to (V
CC
+ 0.3V)
SET0, SET1, SET2 ................................-0.3V to (V
CC
+ 0.3V)
Maximum Current, Any Pin (input/output)...........................20mA
Continuous Power Dissipation (T
A
= +70C)
SOT23-8 (derate 8.75mW/C above +70C)...............700mW
Operating Temperature Range ...........................-40C to +85C
Storage Temperature Range .............................-65C to +150C
Junction Temperature ......................................................+150C
Lead Temperature (soldering, 10s) .................................+300C
V
CC
Rise or Fall Rate......................................................0.05V/s
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Operating Voltage Range
V
CC
2.5
5.5
V
Supply Current
I
CC
No load
8
20
A
Input High Voltage
V
IH
WDI, SET0, SET1, SET2
0.8
V
CC
V
V
CC
3.3V
0.8
Input Low Voltage
V
IL
WDI, SET0, SET1,
SET2
V
CC
2.5V
0.6
V
Logic Input Current (Note 2)
WDI or SET_ = 0 or V
CC
0
10
nA
I
SINK
= 1.2mA, V
CC
> 2.7V, watchdog
output asserted
0.3
V
WDO Output Low
Voltage
V
OL
I
SINK
= 6mA, V
CC
> 4.5V, watchdog
output asserted
0.4
V
WDO Leakage Current
I
LKG
V
NDO
= 0 to +5.5V, output deasserted,
MAX6369/MAX6371/MAX6373
1
A
I
SOURCE
= 500A, V
CC
> 2.7V, watchdog
output deasserted
0.8
V
CC
WDO Output High
Voltage
V
OH
I
SOURCE
= 800A, V
CC
> 4.5V, watchdog
output deasserted
V
CC
- 1.5
V
MAX6369/MAX6370
SET2 = 0, SET1 = 0, SET0 = 0
1
3
SET2 = 0, SET1 = 0, SET0 = V
CC
10
30
SET2 = 0, SET1 = V
CC
, SET0 = 0
30
90
ms
SET2 = 0, SET1 = V
CC
, SET0 = V
CC
Watchdog Disabled
SET2 = V
CC
, SET1 = 0, SET0 = 0
100
300
ms
SET2 = V
CC
, SET1 = 0, SET0 = V
CC
1
3
SET2 = V
CC
, SET1 = V
CC
, SET0 = 0
10
30
Startup Delay Period
t
DELAY
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
60
180
s
MAX6369MAX6374
Pin-Selectable Watchdog Timers
_______________________________________________________________________________________
3
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +2.5V to +5.5V, SET_ = V
CC
or GND, T
A
= -40C to +85C, unless otherwise noted. Typical values are at T
A
= +25C and
V
CC
= +3V.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SET2 = 0, SET1 = 0, SET0 = 0
1
3
SET2 = 0, SET1 = 0, SET0 = V
CC
10
30
SET2 = 0, SET1 = V
CC
, SET0 = 0
30
90
ms
SET2 = 0, SET1 = V
CC
, SET0 = V
CC
Watchdog Disabled
SET2 = V
CC
, SET1 = 0, SET0 = 0
100
300
ms
SET2 = V
CC
, SET1 = 0, SET0 = V
CC
1
3
SET2 = V
CC
, SET1 = V
CC
, SET0 = 0
10
30
Watchdog Timeout
Period
t
WD
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
60
180
s
MAX6371/MAX6372
SET2 = 0, SET1 = V
CC
, SET0 = V
CC
Watchdog Disabled
Startup Delay Period
t
DELAY
All other SET_ conditions
60
180
s
SET2 = 0, SET1 = 0, SET0 = 0
1
3
SET2 = 0, SET1 = 0, SET0 = V
CC
3
9
SET2 = 0, SET1 = V
CC
, SET0 = 0
10
30
ms
SET2 = 0, SET1 = V
CC
, SET0 = V
CC
Watchdog Disabled
SET2 = V
CC
, SET1 = 0, SET0 = 0
100
300
SET2 = V
CC
, SET1 = 0, SET0 = V
CC
300
900
ms
SET2 = V
CC
, SET1 = V
CC
, SET0 = 0
3
9
Watchdog Time-Out
Period
t
WD
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
60
180
s
MAX6373/MAX6374
SET2 = 0, SET1 = 0, SET0 = 0
3
9
ms
SET2 = 0, SET1 = 0, SET0 = V
CC
3
9
SET2 = 0, SET1 = V
CC
, SET0 = 0
60
180
s
SET2 = 0, SET1 = V
CC
, SET0 = V
CC
Watchdog Disabled
SET2 = V
CC
, SET1 = 0, SET0 = 0
200
600
s
SET2 = V
CC
, SET1 = 0, SET0 = V
CC
First Edge (Note 3)
SET2 = V
CC
, SET1 = V
CC
, SET0 = 0
First Edge (Note 3)
Startup Delay Period
t
DELAY
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
60
180
s
SET2 = 0, SET1 = 0, SET0 = 0
3
9
ms
SET2 = 0, SET1 = 0, SET0 = V
CC
3
9
SET2 = 0, SET1 = V
CC
, SET0 = 0
1
3
s
SET2 = 0, SET1 = V
CC
, SET0 = V
CC
Watchdog Disabled
SET2 = V
CC
, SET1 = 0, SET0 = 0
30
90
s
SET2 = V
CC
, SET1 = 0, SET0 = V
CC
1
3
SET2 = V
CC
, SET1 = V
CC
, SET0 = 0
10
30
Watchdog Timeout
Period
t
WD
SET2 = V
CC
, SET1 = V
CC
, SET0 = V
CC
10
30
s
MAX6369MAX6374
Pin-Selectable Watchdog Timers
4
_______________________________________________________________________________________
4
6
10
8
12
14
-40
10
-15
35
60
85
SUPPLY CURRENT
vs. TEMPERATURE
MAX6369/74-01
TEMPERATURE (
C)
SUPPLY CURRENT (
A)
V
CC
= +5.5V
V
CC
= +2.5V
Typical Operating Characteristics
(Circuit of Figure 1, T
A
= +25C, unless otherwise noted
.)
0.997
0.999
0.998
1.001
1.000
1.002
1.003
-40
10
-15
35
60
85
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
MAX6369/74-02
TEMPERATURE (C)
NORMALIZED WATCHDOG TIMEOUT PERIOD
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +2.5V to +5.5V, SET_ = V
CC
or GND, T
A
= -40C to +85C, unless otherwise noted. Typical values are at T
A
= +25C and
V
CC
= +3V.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Watchd og Inp ut P ul se Wi d th
( N ote 2)
t
WDI
After WDO deasserted
100
ns
MAX6369/MAX6371/MAX6373
100
300
ms
Watchdog Output Pulse Width
t
WDO
MAX6370/MAX6372/MAX6374
1
3
ms
Internal Setup Time
(Note 4)
t
SETUP
After WDO deasserted
100
300
s
Note 1: Production tested at T
A
= +25C. 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 Selecting
Device Timing for more information.
Note 4: After power-up, or a setting change, there is an internal setup time during which WDI is ignored.
MAX6369MAX6374
Pin-Selectable Watchdog Timers
_______________________________________________________________________________________
5
PIN
NAME
FUNCTION
1
WDI
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.
2
GND
Ground
3
N.C.
Not Connected. Do not make any connection to this pin.
4
SET0
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.
5
SET1
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.
6
SET2
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.
7
WDO
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.
8
V
CC
Supply Voltage (+2.5V to +5.5V)
Table 1. Minimum Timeout Settings
Pin Description
Detailed Description
The MAX6369MAX6374 are flexible watchdog circuits
for monitoring P activity. During normal operation, the
internal timer is cleared each time the P 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 P 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 200s 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
t
DELAY
, t
WD
t
DELAY
= 60s, t
WD
t
DELAY
t
WD
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
200s
30s
1
0
1
1s
300ms
First Edge
1s
1
1
0
10s
3s
First Edge
10s
1
1
1
60s
60s
60s
10s
PDF 
ZIP