Supervisory Circuits with Watchdog and
Manual Reset in 5-Lead SC70 and SOT-23
ADM823/ADM824/ADM825
FEATURES
Precision 2.5 V to 5 V power supply monitor
7 reset threshold options: 2.19 V to 4.63 V
140 ms (min) reset timeout
Watchdog timer with 1.6s timeout (ADM823, ADM824)
Manual reset input (ADM823, ADM825)
Push-pull output stages:
RESET (ADM823)
RESET, RESET (ADM824/ADM825)
Low power consumption (5 µA)
Guaranteed reset output valid to V
CC
= 1 V
Power supply glitch immunity
Specified over automotive temperature range
5-lead SC70 and SOT-23 packages
FUNCTIONAL BLOCK DIAGRAM
ADM823
V
CC
V
CC
V
REF
RESET
GENERATOR
RESET
MR
DEBOUNCE
WATCHDOG
DETECTOR
04534-0-001
GND
WDI
Figure 1.
APPLICATIONS
Microprocessor systems
Computers
Controllers
Intelligent instruments
Portable equipment
GENERAL DESCRIPTION
The ADM823/ADM824/ADM825 are supervisory circuits
which monitor power supply voltage levels and code execution
integrity in microprocessor-based systems. As well as providing
power on reset signals, an on-chip watchdog timer can reset the
microprocessor if it fails to strobe within a preset timeout
period. A reset signal can also be asserted by an external push-
button, through a manual reset input. The three parts feature
different combinations of watchdog input, manual reset input
and output stage configuration, as shown in Table 1.
Each part is available in a choice of seven reset threshold
options ranging from 2.19 V to 4.63 V. The reset and watchdog
timeout periods are fixed at 140 ms (min) and 1.6s (typ),
respectively.
The ADM823/ADM824/ADM825 are available in 5-lead SC70
and SOT-23 packages and typically consume only 3 µA, making
them suitable for use in low power portable applications.
Table 1. Selection Table
Output Stage
Part No.
ADM823
ADM824
ADM825
Watchdog Timer
Yes
Yes
–
Manual Reset
Yes
–
Yes
RESET
Push-Pull
Push-Pull
Push-Pull
RESET
–
Push-Pull
Push-Pull
Rev. 0
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However, no responsibility is assumed by Analog Devices for its use, nor for any
infringements of patents or other rights of third parties that may result from its use.
Specifications subject to change without notice. No license is granted by implication
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registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.326.8703
© 2004 Analog Devices, Inc. All rights reserved.
ADM823/ADM824/ADM825
TABLE OF CONTENTS
Specifications..................................................................................... 3
Absolute Maximum Ratings............................................................ 5
ESD Caution.................................................................................. 5
Pin Configurations and Function Descriptions ........................... 6
Typical Performance Characteristics ............................................. 7
Circuit Description........................................................................... 9
Reset Output ................................................................................. 9
Manual Reset Input ...................................................................... 9
Watchdog Input .............................................................................9
Application Information................................................................ 10
Watchdog Input Current ........................................................... 10
Negative-Going V
CC
Transients ................................................ 10
Ensuring Reset Valid to V
CC
= 0 V ........................................... 10
Watchdog Software Considerations......................................... 10
Outline Dimensions ....................................................................... 11
Ordering Guides......................................................................... 11
REVISION HISTORY
10/04—Revision 0: Initial Version
Rev. 0 | Page 2 of 12
ADM823/ADM824/ADM825
SPECIFICATIONS
V
CC
= 4.75 V to 5.5 V for ADM82_L, V
CC
= 4.5 V to 5.5 V for ADM82_M, V
CC
= 3.15 V to 3.6 V for ADM82_T,
V
CC
= 3 V to 3.6 V for ADM82_S, V
CC
= 2.7 V to 3.6 V for ADM82_R, V
CC
= 2.38 V to 2.75 V for ADM82_Z,
V
CC
= 2.25 V to 2.75 V for ADM82_Y, T
A
= T
MIN
to T
MAX
, unless otherwise noted.
Table 2.
Parameter
SUPPLY
V
CC
Operating Voltage Range
Supply Current
Min
1
1.2
10
5
RESET THRESHOLD VOLTAGE
ADM82_L
ADM82_M
ADM82_T
ADM82_S
ADM82_R
ADM82_Z (SC70 only)
ADM82_Y (SC70 only)
RESET THRESHOLD TEMPERATURE COEFFICIENT
RESET THRESHOLD HYSTERESIS
RESET TIMEOUT PERIOD
V
CC
TO RESET DELAY
RESET Output Voltage
140
Typ
Max
5.5
24
12
Unit
V
V
µA
µA
Test Conditions/Comments
T
A
= 0°C to +70°C
T
A
= T
MIN
to T
MAX
WDI and MR unconnected
ADM82_L/M
WDI and MR unconnected
ADM82_T/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
ADM82_L/M
ADM82_T/S/R/Z/Y
V
TH
– V
CC
= 100 mV
V
CC
= V
TH
min, I
SINK
= 3.2 mA,
ADM82_L/M
V
CC
= V
TH
min, I
SINK
= 1.2 mA,
ADM82_T/S/R/Z/Y
T
A
= 0°C to 70°C, V
CC
= 1 V,
V
CC
falling, I
SINK
= 50 µA
V
CC
= V
TH
max, I
SOURCE
= 120 µA,
ADM82_L/M
V
CC
= V
TH
max, I
SOURCE
= 30 µA,
ADM82_T/S/R/Z/Y
V
CC
= V
TH
max, I
SINK
= 3.2 mA,
ADM824L/M, ADM825L/M
V
CC
= V
TH
max, I
SINK
= 1.2 mA,
ADM824T/S/R/Z/Y,
ADM825T/S/R/Z/Y
V
CC
≥
1.8 V, I
SOURCE
= 150 µA
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
4.63
4.38
3.08
2.93
2.63
2.32
2.19
40
10
5
200
40
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
280
0.4
0.3
0.3
V
V
V
V
V
V
V
V
V
V
V
V
V
V
ppm/°C
mV
mV
ms
µs
V
V
V
V
V
V
CC
− 1.5
0.8 × V
CC
RESET Output Voltage
0.4
0.3
V
V
0.8 × V
CC
V
Rev. 0 | Page 3 of 12
ADM823/ADM824/ADM825
Parameter
WATCHDOG INPUT (ADM823, ADM824)
Watchdog Timeout Period
WDI Pulse Width
WDI Input Threshold
V
IL
WDI Input Current
MANUAL RESET INPUT (ADM823, ADM825)
MR Input Threshold
MR Input Pulse Width
MR Glitch Rejection
MR Pull-Up Resistance
MR to Reset Delay
0.7 × V
CC
1
35
100
52
500
75
Min
1.12
50
0.7 × V
CC
−20
120
−15
Typ
1.6
Max
2.40
Unit
s
ns
V
µA
µA
V
V
µs
ns
kΩ
ns
Test Conditions/Comments
V
IL
= 0.4 V, V
IH
= 0.8 × V
CC
0.3 × V
CC
160
V
WDI
= V
CC
, time average
V
WDI
= 0, time average
0.3 × V
CC
Rev. 0 | Page 4 of 12
ADM823/ADM824/ADM825
ABSOLUTE MAXIMUM RATINGS
T
A
= 25°C, unless otherwise noted.
Table 3.
Parameter
V
CC
Output Current (RESET, RESET)
All Other Pins
Operating Temperature Range
Storage Temperature Range
θ
JA
Thermal Impedance
SC70
SOT-23
Lead Temperature
Soldering (10 s)
Vapor Phase (60 s)
Infrared (15 s)
Rating
–0.3 V to +6 V
20 mA
–0.3 V to (V
CC
+ 0.3 V)
–40°C to +125°C
–65°C to +150°C
146°C/W
270°C/W
300°C
215°C
220°C
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only and functional operation of the device at these or
any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
ESD CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on
the human body and test equipment and can discharge without detection. Although this product features
proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy
electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance
degradation or loss of functionality.
Rev. 0 | Page 5 of 12
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