ANALOG DEVICES ADM6821, ADM6822, ADM6823, ADM6824 Service Manual

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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

ically consume only 7 μA, making them suitable for use in

typ
low power, portable applications.

Output Stage

RESET

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: [phone] www.analog.com
Fax: [phone] © 2005 Analog Devices, Inc. All rights reserved.

RESET

ADM6821/ADM6822/ADM6823/ADM6824/ADM6825

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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

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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 MR
WDI and MR

mV

VTH − VCC = 100 mV

RESET not asserted

V

CC

unconnected, VCC = 5.5 V
unconnected, VCC = 3.6 V

= 50 μA

SINK

= 100 μA

SINK

= 1.2 mA

SINK

= 3.2 mA

SINK

= 200 μA

SOURCE

= 500 μA

SOURCE

= 800 μA

SOURCE

= 1 μA

SOURCE

= 100 μA

SOURCE

= 500 μA

SOURCE

= 800 μA

SOURCE

= 500 μA

SINK

= 1.2 mA

SINK

= 3.2 mA

SINK

Rev. 0 | Page 3 of 12

ADM6821/ADM6822/ADM6823/ADM6824/ADM6825

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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