19-1838; Rev 4; 12/05
µP Supervisory Circuits with Windowed
(Min/Max) Watchdog and Manual Reset
General Description
The MAX6323/MAX6324 microprocessor (µP) supervi-
sory circuits monitor power supplies and µP activity in
digital systems. A watchdog timer looks for activity out-
side an expected window of operation. Six laser-
trimmed reset thresholds are available with ±2.5%
accuracy from +2.32V to +4.63V. Valid
RESET
output is
guaranteed down to V
CC
= +1.2V.
The
RESET
output is either push-pull (MAX6323) or
open-drain (MAX6324).
RESET
is asserted low when
V
CC
falls below the reset threshold, or when the manual
reset input (MR) is asserted low.
RESET
remains assert-
ed for at least 100ms after V
CC
rises above the reset
threshold and
MR
is deasserted.
The watchdog pulse output (WDPO) utilizes an open-
drain configuration. It can be triggered either by a fast
timeout fault (watchdog input pulses are too close to
each other) or a slow timeout fault (no watchdog input
pulse is observed within the timeout period). The
watchdog timeout is measured from the last falling
edge of watchdog input (WDI) with a minimum pulse
width of 300ns.
WDPO
is asserted for 1ms when a fault
is observed. Eight laser-trimmed timeout periods are
available.
The MAX6323/MAX6324 are offered in a 6-pin SOT23
package and operate over the extended temperature
range (-40°C to +125°C).
♦
Min/Max (Windowed) Watchdog,
8 Factory-Trimmed Timing Options
♦
Pulsed Open-Drain, Active-Low Watchdog Output
♦
Power-On Reset
♦
Precision Monitoring of +2.5V, +3.0V, +3.3V,
and +5.0V Power Supplies
♦
Open-Drain or Push-Pull
RESET
Outputs
♦
Low-Power Operation (23µA typ)
♦
Debounced Manual Reset Input
♦
Guaranteed Reset Valid to V
CC
= +1.2V
Features
MAX6323/MAX6324
Ordering Information
PART*
TEMP
RANGE
PIN-
PACKAGE
RESET
OUTPUT
Applications
Automotive
Industrial
Medical
Embedded Control Systems
MAX6323_UT__-T
-40°C to +125°C 6 SOT23-6 Push-Pull
MAX6324_UT__-T
-40°C to +125°C 6 SOT23-6 Open Drain
*These devices are factory trimmed to one of eight watchdog-
timeout windows and one of six reset voltage thresholds. Insert
the letter corresponding to the desired watchdog-timeout window
(A, B, C, D, E, F, G, or H) into the blank following the number
6323 or 6324 (see Watchdog Timeout table). Insert the two-digit
code (46, 44, 31, 29, 26, or 23) after the letters UT for the desired
nominal reset threshold (see Reset Threshold Range table at end
of data sheet).
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Note:
There are eight standard versions of each device available
(see Standard Versions table). Sample stock is generally held on
standard versions only. Standard versions have an order incre-
ment requirement of 2500 pieces. Nonstandard versions have an
order increment requirement of 10,000 pieces. Contact factory for
availability of nonstandard versions.
Pin Configuration
TOP VIEW
MR
1
6
RESET
Watchdog Timeout
SUFFIX
A
B
C
D
E
F
G
H
WATCHDOG TIMEOUT*
FAST
SLOW
MAX
MIN
UNITS
UNITS
1.5
ms
10
15
ms
100
ms
15
ms
300
15
ms
10
s
15
ms
60
23
ms
47
ms
39
ms
82
719
ms
1.3
s
1
GND
2
MAX6323
MAX6324
5
WDPO
WDI
3
4
V
CC
SOT23
Typical Operating Circuit appears at end of data sheet.
*See
Figure 1 for operation.
________________________________________________________________
Maxim Integrated Products
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.
µP Supervisory Circuits with Windowed
(Min/Max) Watchdog and Manual Reset
MAX6323/MAX6324
ABSOLUTE MAXIMUM RATINGS
Terminal Voltage (with respect to GND)
V
CC
..................................................................-0.3V to +6.0V
MR, RESET
(MAX6323), WDI .............-0.3V to (V
CC
+ +0.3V)
WDPO, RESET
(MAX6324) ..............................-0.3V to +6.0V
Input Current, V
CC
, WDI,
MR
..............................................20mA
Output Current,
RESET, WDPO
..........................................20mA
Rate of Rise, V
CC
............................................................100V/µs
Continuous Power Dissipation (T
A
= +70°C)
6-Pin SOT23 (derate 8.7mW/°C above +70°C) ..........696mW
Operating Temperature Range .........................-40°C to +125°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°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
= full range, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
CC
= 3V, T
A
= +25°C.) (Note 1)
PARAMETER
Operating Voltage Range
Supply Current
SYMBOL
V
CC
I
CC
No load,
RESET
deasserted
MAX632_ _UT46
MAX632_ _UT44
Reset Threshold Voltage
V
TH
MAX632_ _UT31
MAX632_ _UT29
MAX632_ _UT26
MAX632_ _UT23
Reset Timeout Delay
V
CC
to
RESET
Delay
t
RP
RESET
deasserted
10mV/ms, V
TH
+100mV to V
TH
-100mV
I
SINK
= 1.2mA, V
CC
= 2.25V (MAX632_ _UT23,
MAX632_ _UT26, MAX632_ _UT29,
MAX632_ _UT31)
WDPO, RESET
Output Voltage
V
OL
I
SINK
= 3.2mA, V
CC
= 4.25V (MAX632_ _UT44,
MAX632_ _UT46)
I
SINK
= 100µA, V
CC
> 1.2V,
RESET
asserted
I
SOURCE
= 500µA, V
CC
= 3.15V,
RESET
deasserted (MAX632_ _UT23, MAX632_ _UT26, 0.8 x V
CC
MAX632_ _UT29, MAX632_ _UT31)
I
SOURCE
= 800µA, V
CC
= 4.75V,
RESET
V
- 1.5
deasserted, (MAX632_ _UT44, MAX632_ _UT46)
CC
I
LKG
V
RESET
= V
WDPO
= +5.5V,
RESET, WDPO
deasserted
1
µA
V
CC
= 2.5V or 3.3V
V
CC
= 5.5V
4.50
4.25
3.00
2.85
2.55
2.25
100
CONDITIONS
MIN
1.2
23
27
4.63
4.38
3.08
2.93
2.63
2.32
180
20
0.4
V
0.4
0.4
TYP
MAX
5.5
45
57
4.75
4.50
3.15
3.00
2.70
2.38
280
ms
µs
V
UNITS
V
µA
RESET
Output Voltage
(MAX6323)
V
OH
V
WDPO, RESET
Output Leakage
2
_______________________________________________________________________________________
µP Supervisory Circuits with Windowed
(Min/Max) Watchdog and Manual Reset
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= full range, T
A
= -40°C to +125°C, unless otherwise noted. Typical values are at V
CC
= 3V, T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MAX632_AUT_ _
MAX632_BUT_ _
MAX632_CUT_ _
Watchdog Timeout (Fast)
(Notes 2, 3)
t
WD1
MAX632_DUT_ _
MAX632_EUT_ _
MAX632_FUT_ _
MAX632_GUT_ _
MAX632_HUT_ _
MAX632_AUT_ _
MAX632_BUT_ _
MAX632_CUT_ _
Watchdog Timeout (Slow)
(Note 4)
t
WD2
MAX632_DUT_ _
MAX632_EUT_ _
MAX632_FUT_ _
MAX632_GUT_ _
MAX632_HUT_ _
Minimum Watchdog Input
Pulse Width
WDI Glitch Immunity
WDI Input Voltage
WDI Input Current
WDPO
Pulse Width
MANUAL RESET INPUT
MR
Input Voltage
MR
Minimum Pulse Width
MR
Glitch Immunity
MR
to Reset Delay
MR
Pullup Resistance
V
CC
= 2.5V
V
CC
= 2.5V
50
V
IH
V
IL
1
100
120
85
0.7 x V
CC
0.3 x V
CC
V
µs
ns
ns
kΩ
V
IH
V
IL
WDI = 0
WDI = V
CC
V
IL
= 0.8V, V
IH
= 0.75V x V
CC
0.5
-1.5
-1
1
1
1.5
3
V
CC
= 5.5V
0.75 x V
CC
0.8
MIN
1
10
10
10
10
17
29
543
10
100
300
10
60
47
82
1.3
300
100
TYP
MAX
1.5
15
15
15
15
23
39
719
15
150
450
15
90
63
108
1.8
s
ms
s
ns
ns
V
µA
ms
ms
ms
UNITS
WATCHDOG INPUT AND OUTPUT
MAX6323/MAX6324
3
Note 1:
Devices are tested at T
A
= +25°C and guaranteed by design for T
A
= T
MIN
to T
MAX
, as specified.
Note 2:
WDPO
will pulse low if a falling edge is detected on WDI before this timeout period expires.
Note 3:
To avoid a potential fake fault, the first WDI pulse after the rising edge of
RESET
or
WDPO
will not create a fast watchdog
timeout fault.
Note 4:
WDPO
will pulse low if no falling edge is detected on WDI after this timeout period expires.
_______________________________________________________________________________________
µP Supervisory Circuits with Windowed
(Min/Max) Watchdog and Manual Reset
MAX6323/MAX6324
Typical Operating Characteristics
(V
CC
= full range, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX6323/24-01
POWER-DOWN RESET DELAY
vs. TEMPERATURE
MAX6323/24-02
MR TO RESET DELAY
vs. TEMPERATURE
140
MR TO RESET DELAY (ns)
120
100
80
60
40
20
0
MAX6323/24-03
40
35
SUPPLY CURRENT (µA)
30
25
20
15
10
5
0
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
V
CC
= 1.0V
V
CC
= 3.3V
V
CC
= 5.5V
30
POWER-DOWN RESET DELAY (µs)
25
20
15
10
5
0
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
V
OD
= 20mV
160
V
OD
= 100mV
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
MAX6323/24-04
NORMALIZED POWER-UP RESET TIMEOUT
vs. TEMPERATURE
NORMALIZED WATCHDOG TIMEOUT PERIOD (FAST)
MAX6323/24-05
NORMALIZED WATCHDOG TIMEOUT
PERIOD (FAST) vs. TEMPERATURE
1.006
1.004
1.002
1.000
0.998
0.996
0.994
0.992
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
MAX6323/24-06
1.0005
1.0000
RESET THRESHOLD
1.008
1.006
POWER-UP RESET TIMEOUT
1.004
1.002
1.000
0.998
0.996
1.008
0.9995
0.9990
0.9985
0.9980
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
0.994
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
NORMALIZED WATCHDOG OUTPUT PULSE WIDTH (µs)
NORMALIZED WATCHDOG TIMEOUT
PERIOD (SLOW) vs. TEMPERATURE
NORMALIZED WATCHDOG TIMEOUT PERIOD (SLOW)
MAX6323/24-07
NORMALIZED WATCHDOG OUTPUT
PULSE WIDTH vs. TEMPERATURE
MAX6323/24-08
MAXIMUM TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
V
OD
= V
TH
- V
CC
MAXIMUM TRANSIENT DURATION (µs)
350
300
250
200
150
100
50
0
1
10
MAX632_AUT23
100
1000
RESET ASSERTED
ABOVE THIS LINE
MAX6323/24-09
1.003
1.002
1.001
1.000
0.999
0.998
0.997
0.996
0.995
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
1.008
1.006
1.004
1.002
1.000
0.998
0.996
0.994
0.992
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
400
RESET COMPARATOR OVERDRIVE (mV)
4
_______________________________________________________________________________________
µP Supervisory Circuits with Windowed
(Min/Max) Watchdog and Manual Reset
MAX6323/MAX6324
Typical Operating Characteristics (continued)
(V
CC
= full range, T
A
= +25°C, unless otherwise noted.)
SLOW WATCHDOG TIMEOUT PERIOD
MAX6323/24-11
FAST WATCHDOG TIMEOUT PERIOD
MAX6323/24-10
WDI
2V/div
WDI
2V/div
WDPO
2V/div
WDPO
2V/div
MAX6323AUT23
500µs/div
MAX6323AUT23
5ms/div
Pin Description
PIN
NAME
FUNCTION
Active-Low, Manual Reset Input. When
MR
is asserted low,
RESET
is asserted low, the internal watchdog
timer is reset to zero, and
WDPO
is reset to high impedance (open drain). After the rising edge of
MR,
RESET
is asserted for at least 100ms. Leave
MR
unconnected or connect to V
CC
if unused.
Ground
Watchdog Input. The internal watchdog timer clears to zero on the falling edge of WDI or when
RESET
goes
high. If WDI sees another falling edge within the factory-trimmed watchdog window,
WDPO
will remain
unasserted. Transitions outside this window, either faster or slower, will cause
WDPO
to pulse low for 1ms
(typ).
Supply Voltage for the Device. Input for V
CC
reset monitor. For noisy systems, bypass V
CC
with a 500pF
(min) capacitor.
Watchdog Pulse Output. The open-drain
WDPO
output is pulsed low for 1ms (typ) upon detection of a fast
or slow watchdog fault.
WDPO
is only active when
RESET
is high.
Active-Low. Reset is asserted when V
CC
drops below V
TH
and remains asserted until V
CC
rises above V
TH
for the duration of the reset timeout period. The MAX6323 has a push-pull output and the MAX6324 has an
open-drain output. Connect a pullup resistor from
RESET
to any supply voltage up to +6V.
1
MR
2
GND
3
WDI
4
V
CC
WDPO
5
6
RESET
_______________________________________________________________________________________
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