19-0487; Rev 5; 12/05
5-Pin Microprocessor Supervisory Circuits With
Watchdog Timer and Manual Reset
________________General Description
The MAX823/MAX824/MAX825* microprocessor (µP)
supervisory circuits combine reset output, watchdog,
and manual reset input functions in 5-pin SOT23 and
SC70 packages. They significantly improve system relia-
bility and accuracy compared to separate ICs or discrete
components. The MAX823/MAX824/MAX825 are specifi-
cally designed to ignore fast transients on V
CC
.
Seven preprogrammed reset threshold voltages are
available (see
Reset Threshold Table).
All three devices
have an active-low reset output, which is guaranteed to
be in the correct state for V
CC
down to 1V. The MAX823
also offers a watchdog input and manual reset input.
The MAX824 offers a watchdog input and a comple-
mentary active-high reset. The MAX825 offers a manual
reset input and a complementary active-high reset. The
Selector Guide
explains the functions offered in this
series of parts.
*Patents Pending
Features
♦
Precision Monitoring of +2.5V, +3V, +3.3V, and
+5V Power Supplies
♦
Operating Current: 6µA (MAX823L/M) (SC70)
2µA (MAX825T/S/R/Z/Y) (SC70)
♦
Fully Specified Over Temperature
♦
140ms min Power-On Reset
♦
Guaranteed
RESET
Valid to V
CC
= 1V
♦
Power-Supply Transient Immunity
♦
Watchdog Timer with 1.6s Timeout
(MAX823/MAX824)
♦
Manual Reset Input (MAX823/MAX825)
♦
No External Components
MAX823/MAX824/MAX825
Ordering Information
PART
†
MAX823_EXK-T
MAX823_EUK-T
MAX824_EXK-T
TEMP. RANGE
-40°C to +85°C
-40°C to +125°C
-40°C to +85°C
PIN-PACKAGE
5 SC70-5
5 SOT23-5
5 SC70-5
________________________Applications
Computers and Controllers
Embedded Controllers
Intelligent Instruments
Automotive Systems
Critical µP Monitoring
Portable/Battery-Powered Equipment
†Insert
the desired suffix letter (from the Reset Threshold table) into
the blank to complete the part number. All devices are available in
tape-and-reel only. There is a 2500 piece minimum order increment.
Devices are available in both leaded and lead-free packaging.
Specify lead-free by replacing “-T” with “+T” when ordering.
Ordering Information continued at end of data sheet.
Reset Threshold Table
SUFFIX
L
M
T
S
R
Z (SC70 only)
Y (SC70 only)
RESET
THRESHOLD (V)
4.63
4.38
3.08
2.93
2.63
2.32
2.19
______________________Selector Guide
FUNCTION
Active-Low Reset
Active-High Reset
Watchdog Input
Manual Reset Input
MAX823
✔
—
✔
✔
MAX824
✔
✔
✔
—
MAX825
✔
✔
—
✔
Typical Operating Circuit appears at end of data sheet.
Marking Information appears at end of data sheet.
Pin Configurations
TOP VIEW
RESET
1
5
V
CC
RESET
1
5
V
CC
RESET
1
5
V
CC
GND
2
MAX823
GND
2
MAX824
GND
2
MAX825
MR
3
4
WDI
RESET
3
4
WDI
RESET
3
4
MR
SOT23/SC70
SOT23/SC70
SOT23/SC70
________________________________________________________________
Maxim Integrated Products
1
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.
5-Pin Microprocessor Supervisory Circuits With
Watchdog Timer and Manual Reset
MAX823/MAX824/MAX825
ABSOLUTE MAXIMUM RATINGS
V
CC
........................................................................-0.3V to +6.0V
All Other Pins..............................................-0.3V to (V
CC
+ 0.3V)
Input Current, All Pins Except RESET and
RESET..............20mA
Output Current, RESET,
RESET
..........................................20mA
Continuous Power Dissipation (T
A
= +70°C)
5-Pin SC70 (derate 3.1mW/°C above +70°C) ...............247mW
5-Pin SOT23 (derate 7.1mW/°C above +70°C).............571mW
Operating Temperature Range
MAX82_EXK......................................................-40°C to +85°C
MAX82_EUK ...................................................-40°C to +125°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
= +4.75V to +5.5V for MAX82_L, V
CC
= +4.5V to +5.5V for MAX82_M, V
CC
= +3.15V to +3.6V for MAX82_T, V
CC
= +3V
to +3.6V for MAX82_S, V
CC
= +2.7V to +3.6V for MAX82_R, V
CC
= +2.38V to +2.75V for MAX82_Z, V
CC
= +2.25V to +2.75V for
MAX82_Y, T
A
= T
MIN
to T
MAX
, T
A
= -40°C
to +85°C (SC70), T
A
= -40°C to +125°C (SOT23), unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 1)
PARAMETER
Operating Voltage Range
SYMBOL
V
CC
CONDITIONS
T
A
= 0°C to +70°C
T
A
= T
MIN
to T
MAX
WDI and
MR
unconnected
MAX823L/M
MAX824L/M
MAX823T/S/R/Z/Y
MAX824T/S/R/Z/Y
MAX825L/M
MAX825T/S/R/Z/Y
MAX823L/M
MAX824L/M
MAX823T/S/R/Z/Y
MAX824T/S/R/Z/Y
MAX825L/M
MAX825T/S/R/Z/Y
T
A
= +25°C
T
A
= T
MIN
to T
MAX
T
A
= +25°C
T
A
= T
MIN
to T
MAX
T
A
= +25°C
T
A
= T
MIN
to T
MAX
T
A
= +25°C
T
A
= T
MIN
to T
MAX
T
A
= +25°C
T
A
= T
MIN
to T
MAX
T
A
= +25°C
T
A
= T
MIN
to T
MAX
T
A
= +25°C
T
A
= T
MIN
to T
MAX
4.56
4.50
4.31
4.25
3.04
3.00
2.89
2.85
2.59
2.55
2.28
2.25
2.16
2.13
2.19
2.32
2.63
2.93
3.08
4.38
MIN
1.0
1.2
10
5
4.5
3
6
4
3
2
4.63
24
12
12
8
17
12
8
6
4.70
4.75
4.45
4.50
3.11
3.15
2.96
3.00
2.66
2.70
2.35
2.38
2.22
2.25
V
µA
µA
TYP
MAX
5.5
UNITS
V
Supply Current
(SOT23 Only)
I
SUPPLY
MR
unconnected
Supply Current
(SC70 Only)
I
SUPPLY
WDI and
MR
unconnected
MR
unconnected
MAX82_L
MAX82_M
MAX82_T
Reset Threshold
V
RST
MAX82_S
MAX82_R
MAX82_Z
(SC70 only)
MAX82_Y
(SC70 only)
2
_______________________________________________________________________________________
5-Pin Microprocessor Supervisory Circuits With
Watchdog Timer and Manual Reset
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +4.75V to +5.5V for MAX82_L, V
CC
= +4.5V to +5.5V for MAX82_M, V
CC
= +3.15V to +3.6V for MAX82_T, V
CC
= +3V
to +3.6V for MAX82_S, V
CC
= +2.7V to +3.6V for MAX82_R, V
CC
= +2.38V to +2.75V for MAX82_Z, V
CC
= +2.25V to +2.75V for
MAX82_Y, T
A
= T
MIN
to T
MAX
, T
A
= -40°C to +85°C (SC70), T
A
= -40°C to +125°C (SOT23), unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 1)
PARAMETER
Reset Threshold Hysteresis
Reset Threshold Temperature
Coefficient
Reset Timeout Period
V
CC
to
RESET
Delay
t
RP
V
RST
- V
CC
= 100mV
MAX82_L/M, V
CC
= V
RST
max,
I
SOURCE
= 120µA
MAX82_T/S/R/Z/Y, V
CC
= V
RST
max,
I
SOURCE
= 30µA
MAX82_L/M, V
CC
= V
RST
min,
I
SINK
= 3.2mA
MAX82_T/S/R/Z/Y V
CC
= V
RST
min,
I
SINK
= 1.2mA
T
A
= 0°C to +70°C, V
CC
= 1V,
V
CC
falling, I
SINK
= 50µA
T
A
= T
MIN
to T
MAX
, V
CC
= 1.2V,
V
CC
falling, V
BATT
= 0V, I
SINK
= 100µA
RESET
Output Short-Circuit
Current (Note 2)
I
SOURCE
V
OH
RESET Output Voltage
MAX82_L/M,
RESET
= 0V, V
CC
= 5.5V
MAX82_T/S/R/Z/Y,
RESET
= 0V, V
CC
= 3.6V
V
CC
> 1.8V, I
SOURCE
= 150µA
MAX824L/M, MAX825L/M,
V
CC
= V
RST
max, I
SINK
= 3.2mA
MAX824T/S/R/Z/Y, MAX825T/S/R/Z/Y,
V
CC
= V
RST
max, I
SINK
= 1.2mA
1.12
V
IL
= 0.4V, V
IH
= 0.8
✕
V
CC
50
0.3
✕
V
CC
0.7
✕
V
CC
WDI = V
CC
, time average
WDI = 0, time average
-20
120
-15
160
1.60
0.8
✕
V
CC
0.4
0.3
V
800
400
µA
V
CC -
1.5
0.8
✕
V
CC
0.4
V
0.3
0.3
140
SYMBOL
MAX82_L/M
MAX82_T/S/R/Z/Y
CONDITIONS
MIN
TYP
10
5
40
200
20
280
MAX
UNITS
mV
ppm/°C
ms
µs
MAX823/MAX824/MAX825
V
OH
RESET
Output Voltage
V
OL
V
OL
WATCHDOG INPUT (MAX823/MAX824)
Watchdog Timeout Period
WDI Pulse Width
WDI Input Voltage (Note 3)
WDI Input Current (Note 4)
t
WD
t
WDI
V
IL
V
IH
2.40
s
ns
V
µA
_______________________________________________________________________________________
3
5-Pin Microprocessor Supervisory Circuits With
Watchdog Timer and Manual Reset
MAX823/MAX824/MAX825
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +4.75V to +5.5V for MAX82_L, V
CC
= +4.5V to +5.5V for MAX82_M, V
CC
= +3.15V to +3.6V for MAX82_T, V
CC
= +3V
to +3.6V for MAX82_S, V
CC
= +2.7V to +3.6V for MAX82_R, V
CC
= +2.38V to +2.75V for MAX82_Z, V
CC
= +2.25V to +2.75V for
MAX82_Y, T
A
= T
MIN
to T
MAX
, T
A
= -40°C to +85°C (SC70), T
A
= -40°C to +125°C (SOT23), unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
V
IL
V
IH
0.7
✕
V
CC
1.0
100
500
35
52
75
CONDITIONS
MIN
TYP
MAX
UNITS
MANUAL RESET INPUT (MAX823/MAX825)
MR
Input Voltage
MR
Pulse Width
MR
Noise Immunity (pulse width
with no reset)
MR
to Reset Delay
MR
Pullup Resistance
(internal)
0.3
✕
V
CC
V
µs
ns
ns
kΩ
Note 1:
Note 2:
Note 3:
Note 4:
Over-temperature limits are guaranteed by design and not production tested.
The
RESET
short-circuit current is the maximum pullup current when
RESET
is driven low by a µP bidirectional reset pin.
WDI is internally serviced within the watchdog period if WDI is left unconnected.
The WDI input current is specified as the average input current when the WDI input is driven high or low. The WDI input is
designed to drive a three-stated output device with a 10µA maximum leakage current and a maximum capacitive load of
200pF. This output device must be able to source and sink at least 200µA when active.
4
_______________________________________________________________________________________
5-Pin Microprocessor Supervisory Circuits With
Watchdog Timer and Manual Reset
MAX823/MAX824/MAX825
__________________________________________Typical Operating Characteristics
MAX823_, V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
V
CC
SUPPLY CURRENT
vs. TEMPERATURE
MAX823/4/5 toc01
RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX823/4/5 toc02
RESET COMPARATOR PROPAGATION DELAY
vs. TEMPERATURE
V
CC
FALLING
PROPAGATION DELAY (µs)
25
20
15
10
5
0
MAX823/4/5 toc03
9
(SC70 ONLY)
8
SUPPLY CURRENT (µA)
7
6
5
4
3
MAX825R
2
1
-40 -20
0
20
40
60
80
100 120
TEMPERATURE (°C)
MAX824Y
MAX823L
250
240
RESET TIMEOUT PERIOD (ms)
230
220
210
200
190
180
170
160
150
-40
-20
0
20
40
60
80
30
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
MAX823/4/5 toc04
NORMALIZED RESET THRESHOLD
VOLTAGE vs. TEMPERATURE
MAX823/4/5 toc05
MAXIMUM V
CC
TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
45
TRANSIENT DURATION (µs)
40
35
30
25
20
15
10
5
MAX82_L
0
20 40 60 80 100 120 140 160 180 200
RESET OCCURS
ABOVE CURVE
MAX82_Y
MAX82_R
(SC70 ONLY)
MAX823/4/5 toc06
2.0
WATCHDOG TIMEOUT PERIOD (s)
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
-40
-20
0
20
40
60
80
1.06
NORMALIZED RESET THRESHOLD (V)
1.04
1.02
1.00
0.98
0.96
0.94
50
0
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
RESET THRESHOLD OVERDRIVE (mV), V
RST
- V
CC
100
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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