ANALOG DEVICES ADM6825 Service Manual
Low Voltage Supervisory Circuits with
FEATURES
Precision low voltage monitoring
9 reset threshold options: 1.58 V to 4.63 V
140 ms (min) reset timeout
Watchdog timer with 1.6 sec timeout
Manual reset input
Reset output stages
Push-pull active-low
Open-drain active-low
Push-pull active-high
Low power consumption (7 μA)
Guaranteed reset output valid to V
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
= 1 V
CC
Watchdog and Manual Reset in 5-Lead SOT-23
ADM6821/ADM6822/ADM6823/ADM6824/ADM6825
FUNCTIONAL BLOCK DIAGRAM
ADM6823
V
MR
CC
V
REF
DEBOUNCE
GND WDI
RESET
GENERATOR
WATCHDOG
DETECTOR
Figure 1.
V
CC
RESET
04535-001
GENERAL DESCRIPTION
The ADM682x are supervisory circuits that 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 parts
feature different combinations of watchdog input and manual
reset input and output stage configurations, as shown in
Tabl e 1.
Table 1. Selection Table
Part No. Watchdog Timer Manual 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
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable.
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
or otherwise under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective owners.
Each part is available in nine reset threshold options, ranging
from 1.58 V to 4.63 V. The reset and watchdog timeout periods
are fixed at 140 ms (min) and 1.6 sec (typ), respectively.
The ADM682x are available in 5-lead SOT-23 packages and
typically consume only 7 μA, making them suitable for use in
low power, portable applications.
Output Stage
RESET
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 © 2005 Analog Devices, Inc. All rights reserved.
RESET
ADM6821/ADM6822/ADM6823/ADM6824/ADM6825
TABLE OF CONTENTS
Specifications..................................................................................... 3
Watc h d og I nput .............................................................................9
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
REVISION HISTORY
6/05—Revision 0: Initial Version
Application Information................................................................ 10
Watc h d og I nput C ur r ent ........................................................... 10
Negative-Going V
Ensuring Reset Valid to V
Watchdog Software Considerations......................................... 10
Outline Dimensions ....................................................................... 11
Ordering Guide .......................................................................... 11
Transi e n t s ................................................ 10
CC
= 0 V........................................... 10
CC
Rev. 0 | Page 2 of 12
ADM6821/ADM6822/ADM6823/ADM6824/ADM6825
SPECIFICATIONS
VCC = 4.5 V to 5.5 V for ADM682_L/M; VCC = 2.7 V to 3.6 V for ADM682_T/S/R; VCC = 2.1 V to 2.75 V for ADM682_Z/Y; VCC = 1.53 V
to 2.0 V for ADM682_W/V; T
Table 2.
Parameter Min Typ Max Unit Test Conditions/Comments
SUPPLY
VCC Operating Voltage Range 1 5.5 V
Supply Current 10 20 μA
7 16 μA
RESET THRESHOLD VOLTAGE
ADM682xL
ADM682xM
ADM682xT
ADM682xS
ADM682xR
ADM682xZ
ADM682xY
ADM682xW
ADM682xV
RESET THRESHOLD TEMPERATURE COEFFICIENT 60 ppm/°C
RESET THRESHOLD HYSTERESIS 2 x V
VCC TO RESET DELAY 20 μs
RESET TIMEOUT PERIOD 140 200 280 ms
RESET Output Voltage
VOL (Push-Pull or Open-Drain) 0.3 V VCC > = 1 V, I
0.3 V VCC > = 1.2 V, I
0.3 V VCC > = 2.55 V, I
0.4 V VCC > = 4.25 V, I
VOH (Push-Pull Only) 0.8 × V
0.8 × V
0.8 × V
RESET OUTPUT LEAKAGE CURRENT (Open-Drain
Only)
RESET OUTPUT VOLTAGE (Push-Pull Only)
V
OH
0.8 × V
0.8 × V
0.8 × V
V
OL
0.3 V VCC > = 3.15 V, I
0.4 V VCC > = 4.75 V, I
MANUAL RESET INPUT
(ADM6821/ADM6822/ADM6823/ADM6825)
MR Input Threshold
V
IL
V
IH
MR Input Pulse Width
MR Glitch Rejection
MR to Reset Delay
MR Pull-Up Resistance
= –40°C to +125°C, unless otherwise noted.
A
4.50 4.63 4.75 V
4.25 4.38 4.50 V
3.00 3.08 3.15 V
2.85 2.93 3.00 V
2.55 2.63 2.70 V
2.25 2.32 2.38 V
2.12 2.19 2.25 V
1.62 1.67 1.71 V
1.52 1.58 1.62 V
TH
V VCC > = 1.8 V, I
CC
V VCC > = 3.15 V, I
CC
V VCC > = 4.75 V, I
CC
1 μA
0.8 × V
V VCC > = 1 V, I
CC
V VCC > = 1.5 V, I
CC
V VCC > = 2.55 V, I
CC
V VCC > = 4.25 V, I
CC
0.3 V VCC > = 1.8 V, I
0.3 × V
0.7 × V
V
CC
1 μs
100 ns
200 ns
25 50 75 kΩ
WDI and
WDI and
MR unconnected, VCC = 5.5 V
MR unconnected, VCC = 3.6 V
mV
VTH − VCC = 100 mV
RESET not asserted
V
CC
= 50 μA
SINK
SINK
SINK
SINK
SOURCE
SOURCE
SOURCE
SOURCE
SOURCE
SOURCE
SOURCE
SINK
SINK
SINK
= 100 μA
= 1.2 mA
= 3.2 mA
= 200 μA
= 500 μA
= 800 μA
= 1 μA
= 100 μA
= 500 μA
= 800 μA
= 500 μA
= 1.2 mA
= 3.2 mA
Rev. 0 | Page 3 of 12
ADM6821/ADM6822/ADM6823/ADM6824/ADM6825
Parameter Min Typ Max Unit Test Conditions/Comments
WATCHDOG INPUT
(ADM6821/ADM6822/ADM6823/ADM6824)
Watchdog Timeout Period 1.12 1.6 2.40 sec
WDI Pulse Width 50 ns
WDI Input Threshold
V
IL
V
IH
WDI Input Current 120 160 μA V
0.3 × V
0.7 × V
−20 −15
V
CC
μA V
V
CC
WDI
WDI
= V
= 0
CC
Rev. 0 | Page 4 of 12
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