19-0487; Rev 1; 6/97
5-Pin Microprocessor Supervisory Circuits
_______________General Description
The MAX823/MAX824/MAX825* microprocessor (µP)
supervisory circuits combine reset output, watchdog,
and manual-reset input functions in a 5-pin SOT23-5
package. They significantly improve system reliability
and accuracy compared to separate ICs or discrete
components. The MAX823/MAX824/MAX825 are
specifically designed to ignore fast transients on V
CC
.
Five preprogrammed reset threshold voltages are
available, designated by the following package
suffixes: L = 4.63V, M = 4.38V, T = 3.08V, S = 2.93V,
and R = 2.63V. 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 MAX824/MAX825 also
have an active-high reset output. The following
Selector
Guide
explains the functions offered in this series of
parts.
____________________________Features
o
Precision Monitoring of +3V, +3.3V, and +5V
Power Supplies
o
Operating Current: 10µA (MAX823L/M)
3µA (MAX825T/S/R)
o
Fully Specified Over Temperature
o
140ms Min Power-On Reset
o
Guaranteed RESET Valid to V
CC
= 1V
o
Power-Supply Transient Immunity
o
Watchdog Timer with 1.6sec Timeout
(MAX823/MAX824)
o
Manual-Reset Input (MAX823/MAX825)
o
No External Components
MAX823/MAX824/MAX825
________________________Applications
Battery-Powered Computers and Controllers
Embedded Controllers
Intelligent Instruments
Automotive Systems
Critical µP Monitoring
Portable/Battery-Powered Equipment
______________Ordering Information
PART
†
MAX823_EUK
MAX824_EUK
MAX825_EUK
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
5 SOT23-5
5 SOT23-5
5 SOT23-5
†
Insert the desired suffix letter (from the table below) into the
blank to complete the part number.
RESET
THRESHOLD (V)
4.63
4.38
3.08
2.93
2.63
_____________________Selector Guide
SUFFIX
FUNCTION
Active-Low Reset
Active-High Reset
Watchdog Input
Manual-Reset Input
—
—
—
MAX823
MAX824
MAX825
L
M
T
S
R
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
SOT23-5
SOT23-5
SOT23-5
*Patents Pending
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
5-Pin Microprocessor Supervisory Circuits
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
Rate of Rise, V
CC
............................................................100V/µs
Continuous Power Dissipation (T
A
= +70°C)
SOT23-5 (derate 7.1mW/°C above +70°C)...................571mW
Operating Temperature Range
MAX82_EUK .....................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+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, T
A
= T
MIN
to T
MAX
, 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
= -40°C to +85°C
WDI and
MR
unconnected
MAX823L/M,
MAX824L/M
MAX823T/S/R,
MAX824T/S/R
MAX825L/M
MAX825T/S/R
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
T
A
= +25°C
T
A
= -40°C to +85°C
4.56
4.50
4.31
4.25
3.04
3.00
2.89
2.85
2.59
2.55
10
5
40
t
RP
MAX82_L/M
MAX82_T/S/R
140
140
200
200
280
280
2.63
2.93
3.08
4.38
MIN
1.0
1.2
10
5
4.5
3
4.63
24
12
12
8
4.70
4.75
4.45
4.50
3.11
3.15
2.96
3.00
2.66
2.70
mV
ppm/°C
ms
V
µA
TYP
MAX
5.5
UNITS
V
Supply Current
I
SUPPLY
MR
unconnected
MAX82_L
MAX82_M
Reset Threshold
V
RST
MAX82_T
MAX82_S
MAX82_R
Reset Threshold Hysteresis
Reset Threshold Temperature
Coefficient
Reset Timeout Period
MAX82_L/M
MAX82_T/S/R
2
_______________________________________________________________________________________
5-Pin Microprocessor Supervisory Circuits
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, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at
T
A
= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MAX82_L/M, V
CC
= V
RST
max,
I
SOURCE
= 120µA
MAX82_T/S/R, V
CC
= V
RST
max,
I
SOURCE
= 30µA
MAX82_L/M, V
CC
= V
RST
min,
I
SINK
= 3.2mA
MAX82_T/S/R, 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
= -40°C to +85°C, 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,
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, MAX825T/S/R,
V
CC
= V
RST
max, I
SINK
= 1.2mA
V
RST
- V
CC
= 100mV
t
WD
t
WDI
V
IL
V
IH
V
IL
= 0.4V, V
IH
= 0.8V
CC
V
CC
= 5V
WDI = V
CC
, time average
WDI = 0V, time average
V
IL
V
IH
1.0
100
500
35
52
75
-20
0.3V
CC
0.7V
CC
1.12
50
0.3V
CC
0.7V
CC
120
-15
160
20
1.60
2.40
0.8V
CC
0.4
0.3
µs
sec
ns
V
µA
V
MIN
V
CC
- 1.5
0.8V
CC
0.4
V
0.3
0.3
0.3
800
400
µA
TYP
MAX
UNITS
MAX823/MAX824/MAX825
V
OH
RESET
Output Voltage
V
OL
V
OL
V
CC
to
RESET
Delay
WATCHDOG INPUT (MAX823/MAX824)
Watchdog Timeout Period
WDI Pulse Width
WDI Input Threshold (Note 3)
WDI Input Current (Note 4)
MANUAL-RESET INPUT (MAX823/MAX825)
MR
Input Threshold
MR
Pulse Width
MR
Noise Immunity (pulse width
with no reset)
MR
to Reset Delay
MR
Pull-Up Resistance (internal)
Note 1:
Note 2:
Note 3:
Note 4:
V
µs
ns
ns
kΩ
Over-temperature limits are guaranteed by design and not production tested.
The
RESET
short-circuit current is the maximum pull-up 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.
_______________________________________________________________________________________
3
5-Pin Microprocessor Supervisory Circuits
MAX823/MAX824/MAX825
__________________________________________Typical Operating Characteristics
(MAX823L, V
CC
= +5V, T
A
= +25°C, unless otherwise noted.)
V
CC
SUPPLY CURRENT
vs. TEMPERATURE
MAX823/4/5-01
RESET TIMEOUT PERIOD
vs. TEMPERATURE
MAX823/4/5-02
RESET COMPARATOR PROPAGATION DELAY
vs. TEMPERATURE
V
CC
FALLING
PROPAGATION DELAY (µs)
25
20
15
10
5
0
MAX823/4/5-03
12.5
12.0
SUPPLY CURRENT (µA)
11.5
11.0
10.5
10.0
9.5
9.0
8.5
8.0
7.5
-40
-20
0
20
40
60
80
250
240
RESET TIMEOUT PERIOD (ms)
230
220
210
200
190
180
170
160
150
30
100
-40
-20
0
20
40
60
80
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
WATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
MAX823/4/5-04
NORMALIZED RESET THRESHOLD
VOLTAGE vs. TEMPERATURE
MAX823/4/5-05
MAXIMUM V
CC
TRANSIENT DURATION
vs. RESET THRESHOLD OVERDRIVE
140
TRANSIENT DURATION (µs)
120
100
80
60
40
20
RESET OCCURS
ABOVE CURVE
MAX823/4/5-06
2.0
WATCHDOG TIMEOUT PERIOD (sec)
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
160
0
-40
-20
0
20
40
60
80
100
0
20 40 60 80 100 120 140 160 180 200
TEMPERATURE (°C)
RESET THRESHOLD OVERDRIVE (mV), V
RST
- V
CC
100
TEMPERATURE (°C)
4
_______________________________________________________________________________________
5-Pin Microprocessor Supervisory Circuits
______________________________________________________________Pin Description
MAX823
PIN
MAX824
MAX825
NAME
FUNCTION
Active-Low Reset Output. Pulses low for 200ms when triggered, and remains
low whenever V
CC
is below the reset threshold or when
MR
is a logic low. It
remains low for 200ms after one of the following occurs: V
CC
rises above the
reset threshold, the watchdog triggers a reset, or
MR
goes low to high.
Ground. 0V reference for all signals.
Manual-Reset Input. A logic low on
MR
asserts reset. Reset remains asserted as
long as
MR
is held low and for 200ms after
MR
returns high. The active-low input
has an internal 52kΩ pull-up resistor. It can be driven from a CMOS-logic line or
shorted to ground with a switch. Leave open or connect to V
CC
if unused.
Active-High Reset Output. Inverse of
RESET.
Watchdog Input. If WDI remains either high or low for longer than the watch-
dog timeout period, the internal watchdog timer runs out and a reset is trig-
gered. The internal watchdog timer clears whenever reset is asserted, or
whenever WDI sees a rising or falling edge. If WDI is left unconnected or is
connected to a three-stated buffer output, the watchdog feature is disabled.
Supply Voltage
MAX823/MAX824/MAX825
1
1
1
RESET
2
2
2
GND
3
—
4
MR
—
3
3
RESET
4
4
—
WDI
5
5
5
V
CC
V
CC
MAX823
MAX824
MAX825
RESET
GENERATOR
V
CC
1.25V
RESET
RESET
(MAX824/MAX825
ONLY)
MR
(MAX823/MAX825
ONLY)
WDI
(MAX823/MAX824
ONLY)
WATCHDOG
TRANSITION
DETECTOR
WATCHDOG
TIMER
GND
Figure 1. Functional Diagram
_______________________________________________________________________________________
5
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