Low Voltage Supervisory Circuits with
Watchdog & Manual Reset in 5-Lead SOT-23
Preliminary Technical Data
ADM6821–ADM6825
Rev. PrA
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Specifications subject to change without notice. No license is granted by implication
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registered trademarks are the property of their respective companies.
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Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.
FEATURES
Precision Low Voltage Monitoring down to 1.8V
9 Reset Threshold Options:
1.58V to 4.63V
140ms (Min) Reset Timeout
Watchdog Timer with 1.6s Timeout
Manual Reset Input
Reset Output Stages
Push-Pull Active-Low
Open-Drain Active-Low
Push-Pull Active-High
Low Power Consumption (3µA)
Guaranteed Reset Output valid to VCC=1V
Power Supply Glitch Immunity
Specified from -40°C to +125°C
5-Lead SOT-23 Package
APPLICATIONS
Microprocessor Systems
Computers
Controllers
Intelligent Instruments
Portable Equipment
GENERAL DESCRIPTION
The ADM6821-ADM6825 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 means of 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.
FUNCTIONAL BLOCK DIAGRAM
RESET
GENERATOR
MR
DEBOUNCE
GND
RESET
V
CC
V
REF
V
CC
ADM6821
WATCHDOG
DETECTOR
WDI
Each part is available in a choice of 9 reset threshold options
ranging from 1.58V to 4.63V. The reset and watchdog timeout
periods are fixed at 140ms (min) and 1.6s (typ), respectively.
The ADM6821-ADM6825 are available in 5-lead SOT-23
packages and typically consume only 3µA, making them
suitable for use in low power portable applications.
Table 1. Selection Table
Output Stage
Part No. Watchdog Timer Manual Reset RESET RESET
ADM6821 Yes Yes - Push-Pull
ADM6822 Yes Yes Open-Drain -
ADM6823 Yes Yes Push-Pull -
ADM6824 Yes - Push-Pull Push-Pull
ADM6825 - Yes Push-Pull Push-Pull
ADM6821–ADM6825 Preliminary Technical Data
Rev.PrA | Page 2 of 7
ADM6821–ADM6825—SPECIFICATIONS
Table 2. VCC=4. 5V to 5.5V for ADM682_L/M, VCC=2.7V to 3.6V for ADM682_T/S/R, VCC=2.1V to 2.75V for ADM682_Z/Y,
VCC=1.53V to 2.0V for ADM682_W/V, TA=-40°C to +125°C, unless otherwise noted.
Parameter Min Typ Max Units Test Conditions/Comments
SUPPLY
VCC Operating Voltage Range 1 5.5 V TA=0°C to +70°C
1.2 5.5 V TA=--40°C to +125°C
Supply Current (WDI and MR unconnected) 10 24 µA
VCC=5.5V, no load,
TA=--40°C to +85°C
30 µA
VCC=5.5V, no load,
TA=--40°C to +125°C
7 16 µA
VCC=3.6V, no load,
TA=--40°C to +85°C
25 µA
VCC=3.6V, no load,
TA=--40°C to +125°C
5 12 µA
VCC=3.6V, no load,
TA=--40°C to +85°C
(ADM6825 only)
20 µA
VCC=3.6V, no load,
TA=--40°C to +125°C
(ADM6825 only)
RESET THRESHOLD VOLTAGE
ADM682_L 4.50 4.63 4.75 V TA=-40°C to +85°C
4.47 4.78 V TA=-40°C to +125°C
ADM682_M 4.25 4.38 4.50 V TA=-40°C to +85°C
4.22 4.53 V TA=-40°C to +125°C
ADM682_T 3.00 3.08 3.15 V TA=-40°C to +85°C
2.97 3.17 V TA=-40°C to +125°C
ADM682_S 2.85 2.93 3.00 V TA=-40°C to +85°C
2.83 3.02 V TA=-40°C to +125°C
ADM682_R 2.55 2.63 2.70 V TA=-40°C to +85°C
2.53 2.72 V TA=-40°C to +125°C
ADM682_Z 2.25 2.32 2.38 V TA=-40°C to +85°C
2.24 2.40 V TA=-40°C to +125°C
ADM682_Y 2.12 2.19 2.25 V TA=-40°C to +85°C
2.11 2.27 V TA=-40°C to +125°C
ADM682_W 1.62 1.67 1.71 V TA=-40°C to +85°C
1.61 1.72 V TA=-40°C to +125°C
ADM682_V 1.52 1.58 1.62 V TA=-40°C to +85°C
RESET THRESHOLD TEMPERATURE COEFFICIENT 60 ppm/°C
RESET THRESHOLD HYSTERESIS 2x VTH mV
RESET TIMEOUT PERIOD 140 200 280 ms
100 320 ms
VCC TO RESET DELAY 20 µs VCC = VTH to (VTH - 100mV)
RESET Output Voltage Low 0.4 V
VCC>=4.25V, ISINK=3.2mA, reset
asserted
0.3 V
VCC>=2.55V, ISINK=1.2mA, reset
asserted
0.3 V
VCC>=1.25V, ISINK=100uA, reset
asserted
0.3 V
VCC>=1.0V, ISINK=50uA, reset
asserted, TA=-40°C to +85°C
RESET Output Voltage High 0.8×VCC V
VCC>=4.75V, ISOURCE=800uA,
reset not asserted
Preliminary Technical Data ADM6821–ADM6825
Rev.PrA | Page 3 of 7
Parameter Min Typ Max Units Test Conditions/Comments
0.8×VCC V
VCC>=3.15V, ISOURCE=500uA,
reset not asserted
0.8×VCC V
VCC>=1.8V, ISOURCE=200uA,
reset not asserted
RESET Output Voltage High 0.8×VCC
VCC>=4.25V, ISOURCE=800uA,
reset asserted
0.8×VCC
VCC>=2.55V, ISOURCE=500uA,
reset asserted
0.8×VCC
VCC>=1.50V, ISOURCE=100uA,
reset asserted
0.8×VCC
VCC>=1.0V, ISOURCE=1uA,
reset asserted, TA=-40°C to +85°C
RESET Output Voltage Low 0.4 V VCC>=4.75V, ISINK=3.2mA,
reset not asserted
0.3 V
VCC>=3.15V, ISINK=1.2mA,
reset not asserted
0.3 V
VCC>=1.8V, ISINK=500uA,
reset not asserted
WATCHDOG INPUT (ADM6821-ADM6824)
Watchdog Timeout Period 1.12 1.6 2.40 s
WDI Pulse Width 50 ns VIL=0.4V, VIH=0.8×VCC,
WDI Input Threshold
VIL 0.3xVCC V
VIH 0.7xVCC V
WDI Input Current 120 160 µA VWDI= VCC, time average
-20 -15 µA VWDI=0, time average
MANUAL RESET INPUT (ADM6821-ADM6823/ADM6825)
MR Input Threshold 0.3xVCC V
0.7xVCC V
MR Input Pulse Width 1 µs
MR Glitch Rejection 100 ns
MR Pull-up Resistance 25 50 75 k⍀
MR to Reset Delay 200 ns
ABSOLUTE MAXIMUM RATINGS
Table 3. TA = 25°C unless otherwise noted.
Parameter Rating
VCC -0.3V to +6V
Output Current (RESET, RESET) 20mA
Operating Temperature Range -40°C to +125°C
Storage Temperature Range -65°C to +150°C
θJA Thermal Impedance 270°C/W
Lead Temperature
Soldering (10 sec) 300°C
Vapour Phase (60 sec) 215°C
Infrared (15 sec) 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.
ADM6821–ADM6825 Preliminary Technical Data
Rev.PrA | Page 4 of 7
PIN CONFIGURATIONS AND FUNCTIONAL DESCRIPTIONS
1
2
34
5
ADM6822/
ADM6823
TOP VIEW
(Not to Scale)
VCC
RESET
GND
MR WDI
1
2
34
5
ADM6821
TOP VIEW
(Not to Scale)
VCC
RESET
GND
MR WDI
1
2
34
5
ADM6824
TOP VIEW
(Not to Scale)
VCC
RESET
GND
RESET WDI
1
2
34
5
ADM6825
TOP VIEW
(Not to Scale)
VCC
RESET
GND
RESET MR
Table 4. Pin Functional Descriptions
Pin No. Name Description
1 RESET (ADM6822/23/24/25) Active-Low Reset Output, which is asserted whenever VCC is below the reset.threshold,
VTH.
Open-Drain Output Stage for ADM6822.
Push-Pull Output Stage for ADM6823/24/25.
RESET (ADM6821) Active-High Reset Output
2 GND Ground
3 MR (ADM6821/22/23) Manual Reset Input. This is an active-low input which, when forced low for at least 1µs,
generates a reset.
Features a 52k⍀ internal pull-up.
RESET (ADM6824/ADM6825) Active-High Push-Pull Reset Output.
4 WDI (ADM6821/22/23/24) Watchdog Input. Generates a reset if the voltage on the pin remains low or high for the
duration of the watchdog timeout. The timer is cleared if a logic transition occurs on this
pin or if a reset is generated.
MR (ADM6825) Manual Reset Input.
5 VCC Power Supply Voltage being Monitored
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.
Preliminary Technical Data ADM6821–ADM6825
Rev. PrA | Page 5 of 7
ORDERING GUIDE
Model Reset Threshold (V) Temperature Range Quantity Package Type Branding
ADM6821LART-RL 4.63 -40°C to +125°C 10k SOT-23-5 N0A
ADM6821LART-RL7 4.63 -40°C to +125°C 3k SOT-23-5 N0A
ADM6821MART-RL 4.38 -40°C to +125°C 10k SOT-23-5 N0A
ADM6821MART-RL7 4.38 -40°C to +125°C 3k SOT-23-5 N0A
ADM6821TART-RL 3.08 -40°C to +125°C 10k SOT-23-5 N0A
ADM6821TART-RL7 3.08 -40°C to +125°C 3k SOT-23-5 N0A
ADM6821SART-RL 2.93 -40°C to +125°C 10k SOT-23-5 N0A
ADM6821SART-RL7 2.93 -40°C to +125°C 3k SOT-23-5 N0A
ADM6821RART-RL 2.63 -40°C to +125°C 10k SOT-23-5 N0A
ADM6821RART-RL7 2.63 -40°C to +125°C 3k SOT-23-5 N0A
ADM6821ZART-RL 2.32 -40°C to +125°C 10k SOT-23-5 N0A
ADM6821ZART-RL7 2.32 -40°C to +125°C 3k SOT-23-5 N0A
ADM6821YART-RL 2.19 -40°C to +125°C 10k SOT-23-5 N0A
ADM6821YART-RL7 2.19 -40°C to +125°C 3k SOT-23-5 N0A
ADM6821WART-RL 1.67 -40°C to +125°C 10k SOT-23-5 N0A
ADM6821WART-RL7 1.67 -40°C to +125°C 3k SOT-23-5 N0A
ADM6821VART-RL 1.58 -40°C to +125°C 10k SOT-23-5 N0A
ADM6821VART-RL7 1.58 -40°C to +125°C 3k SOT-23-5 N0A
ADM6822LART-RL 4.63 -40°C to +125°C 10k SOT-23-5 N0B
ADM6822LART-RL7 4.63 -40°C to +125°C 3k SOT-23-5 N0B
ADM6822MART-RL 4.38 -40°C to +125°C 10k SOT-23-5 N0B
ADM6822MART-RL7 4.38 -40°C to +125°C 3k SOT-23-5 N0B
ADM6822TART-RL 3.08 -40°C to +125°C 10k SOT-23-5 N0B
ADM6822TART-RL7 3.08 -40°C to +125°C 3k SOT-23-5 N0B
ADM6822SART-RL 2.93 -40°C to +125°C 10k SOT-23-5 N0B
ADM6822SART-RL7 2.93 -40°C to +125°C 3k SOT-23-5 N0B
ADM6822RART-RL 2.63 -40°C to +125°C 10k SOT-23-5 N0B
ADM6822RART-RL7 2.63 -40°C to +125°C 3k SOT-23-5 N0B
ADM6822ZART-RL 2.32 -40°C to +125°C 10k SOT-23-5 N0B
ADM6822ZART-RL7 2.32 -40°C to +125°C 3k SOT-23-5 N0B
ADM6822YART-RL 2.19 -40°C to +125°C 10k SOT-23-5 N0B
ADM6822YART-RL7 2.19 -40°C to +125°C 3k SOT-23-5 N0B
ADM6822WART-RL 1.67 -40°C to +125°C 10k SOT-23-5 N0B
ADM6822WART-RL7 1.67 -40°C to +125°C 3k SOT-23-5 N0B
ADM6822VART-RL 1.58 -40°C to +125°C 10k SOT-23-5 N0B
ADM6822VART-RL7 1.58 -40°C to +125°C 3k SOT-23-5 N0B
ADM6823LART-RL 4.63 -40°C to +125°C 10k SOT-23-5 N0C
ADM6823LART-RL7 4.63 -40°C to +125°C 3k SOT-23-5 N0C
ADM6823MART-RL 4.38 -40°C to +125°C 10k SOT-23-5 N0C
ADM6823MART-RL7 4.38 -40°C to +125°C 3k SOT-23-5 N0C
ADM6823TART-RL 3.08 -40°C to +125°C 10k SOT-23-5 N0C
ADM6823TART-RL7 3.08 -40°C to +125°C 3k SOT-23-5 N0C
ADM6823SART-RL 2.93 -40°C to +125°C 10k SOT-23-5 N0C
ADM6823SART-RL7 2.93 -40°C to +125°C 3k SOT-23-5 N0C
ADM6823RART-RL 2.63 -40°C to +125°C 10k SOT-23-5 N0C
ADM6823RART-RL7 2.63 -40°C to +125°C 3k SOT-23-5 N0C
ADM6823ZART-RL 2.32 -40°C to +125°C 10k SOT-23-5 N0C
ADM6823ZART-RL7 2.32 -40°C to +125°C 3k SOT-23-5 N0C
ADM6823YART-RL 2.19 -40°C to +125°C 10k SOT-23-5 N0C
ADM6823YART-RL7 2.19 -40°C to +125°C 3k SOT-23-5 N0C
ADM6821–ADM6825 Preliminary Technical Data
Rev.PrA | Page 6 of 7
ORDERING GUIDE (CONTD.)
Model Reset Threshold (V) Temperature Range Quantity Package Type Branding
ADM6823WART-RL 1.67 -40°C to +125°C 10k SOT-23-5 N0C
ADM6823WART-RL7 1.67 -40°C to +125°C 3k SOT-23-5 N0C
ADM6823VART-RL 1.58 -40°C to +125°C 10k SOT-23-5 N0C
ADM6823VART-RL7 1.58 -40°C to +125°C 3k SOT-23-5 N0C
ADM6824LART-RL 4.63 -40°C to +125°C 10k SOT-23-5 N0D
ADM6824LART-RL7 4.63 -40°C to +125°C 3k SOT-23-5 N0D
ADM6824MART-RL 4.38 -40°C to +125°C 10k SOT-23-5 N0D
ADM6824MART-RL7 4.38 -40°C to +125°C 3k SOT-23-5 N0D
ADM6824TART-RL 3.08 -40°C to +125°C 10k SOT-23-5 N0D
ADM6824TART-RL7 3.08 -40°C to +125°C 3k SOT-23-5 N0D
ADM6824SART-RL 2.93 -40°C to +125°C 10k SOT-23-5 N0D
ADM6824SART-RL7 2.93 -40°C to +125°C 3k SOT-23-5 N0D
ADM6824RART-RL 2.63 -40°C to +125°C 10k SOT-23-5 N0D
ADM6824RART-RL7 2.63 -40°C to +125°C 3k SOT-23-5 N0D
ADM6824ZART-RL 2.32 -40°C to +125°C 10k SOT-23-5 N0D
ADM6824ZART-RL7 2.32 -40°C to +125°C 3k SOT-23-5 N0D
ADM6824YART-RL 2.19 -40°C to +125°C 10k SOT-23-5 N0D
ADM6824YART-RL7 2.19 -40°C to +125°C 3k SOT-23-5 N0D
ADM6824WART-RL 1.67 -40°C to +125°C 10k SOT-23-5 N0D
ADM6824WART-RL7 1.67 -40°C to +125°C 3k SOT-23-5 N0D
ADM6824VART-RL 1.58 -40°C to +125°C 10k SOT-23-5 N0D
ADM6824VART-RL7 1.58 -40°C to +125°C 3k SOT-23-5 N0D
ADM6825LART-RL 4.63 -40°C to +125°C 10k SOT-23-5 N0E
ADM6825LART-RL7 4.63 -40°C to +125°C 3k SOT-23-5 N0E
ADM6825MART-RL 4.38 -40°C to +125°C 10k SOT-23-5 N0E
ADM6825MART-RL7 4.38 -40°C to +125°C 3k SOT-23-5 N0E
ADM6825TART-RL 3.08 -40°C to +125°C 10k SOT-23-5 N0E
ADM6825TART-RL7 3.08 -40°C to +125°C 3k SOT-23-5 N0E
ADM6825SART-RL 2.93 -40°C to +125°C 10k SOT-23-5 N0E
ADM6825SART-RL7 2.93 -40°C to +125°C 3k SOT-23-5 N0E
ADM6825RART-RL 2.63 -40°C to +125°C 10k SOT-23-5 N0E
ADM6825RART-RL7 2.63 -40°C to +125°C 3k SOT-23-5 N0E
ADM6825ZART-RL 2.32 -40°C to +125°C 10k SOT-23-5 N0E
ADM6825ZART-RL7 2.32 -40°C to +125°C 3k SOT-23-5 N0E
ADM6825YART-RL 2.19 -40°C to +125°C 10k SOT-23-5 N0E
ADM6825YART-RL7 2.19 -40°C to +125°C 3k SOT-23-5 N0E
ADM6825WART-RL 1.67 -40°C to +125°C 10k SOT-23-5 N0E
ADM6825WART-RL7 1.67 -40°C to +125°C 3k SOT-23-5 N0E
ADM6825VART-RL 1.58 -40°C to +125°C 10k SOT-23-5 N0E
ADM6825VART-RL7 1.58 -40°C to +125°C 3k SOT-23-5 N0E
Preliminary Technical Data ADM6821–ADM6825
Rev. PrA | Page 7 of 7
OUTLINE DIMENSIONS
PIN 1
1.60 BSC 2.80 BSC
1.90
BSC
0.95 BSC
1 3
4 5
2
0.22
0.08
10
5
0
0.50
0.3
0.15 MAX SEATING
PLANE
1.45 MAX
1.30
1.15
0.90
2.90 BSC
0.$
0.45
0.3
COMPLIANT TO JEDEC STANDARDS MO-178AA
Figure 1. 5-Lead Small Outline Transistor Package [SOT-23]
(RT-5)
Dimensions shown in millimeters
© 2004 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective companies.
Printed in the U.S.A.
PR04535-0-2/04(PrA)
