Analog Devices ADM6821 25 prb Datasheet
Low Voltage Supervisory Circuits with
Watchdog and Manual Reset in 5-Lead SOT-23
Preliminary Technical Data
FEATURES
Precision low voltage monitoring down to 1.8 V
9 reset threshold options:
1.58 V to 4.63 V
140 ms (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 (3 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
GENERAL DESCRIPTION
The ADM6821–ADM6825 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, manual reset
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
= 1 V
CC
ADM6821–ADM6825
FUNCTIONAL BLOCK DIAGRAM
V
ADM6823
V
MR
CC
V
REF
DEBOUNCE
GND
RESET
GENERATOR
WATCHDOG
DETECTOR
WDI
Figure 1.
input and output stage configuration, as shown in table 1.
Each part is available in a choice of 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 1.6s (typ), respectively.
The ADM6821–ADM6825 are available in 5-lead SOT-23
packages and typically consume only 3 µA, making them
suitable for use in low power portable applications.
Output Stage
RESET
RESET
CC
RESET
Rev. PrB
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.
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 © 2005 Analog Devices, Inc. All rights reserved.
ADM6821–ADM6825 Preliminary Technical Data
TABLE OF CONTENTS
Specifications..................................................................................... 3
Watchdog Input.............................................................................9
Absolute Maximum Ratings............................................................ 5
ESD Caution.................................................................................. 5
Pin Configurations And Functional Descriptions ....................... 6
Typical Performance Characteristics ............................................. 7
Circuit Description........................................................................... 9
Reset Output ................................................................................. 9
Manual Reset Input ...................................................................... 9
REVISION HISTORY
Revision 0: Initial Version
Application Information................................................................ 10
Watchdog Input Current........................................................... 10
Negative-Going V
Ensuring Reset Valid to V
Watchdog Software Considerations......................................... 10
Outline Dimensions....................................................................... 11
ORDERING GUIDE.................................................................. 11
Transients ................................................ 10
CC
= 0 V............................................ 10
CC
Rev. PrB | Page 2 of 11
Preliminary Technical Data ADM6821–ADM6825
SPECIFICATIONS
Table 1. 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, V
Parameter Min Typ Max Unit Test Conditions/Comments
SUPPLY
VCC Operating Voltage Range 1 5.5 V TA = 0°C to +85°C
1.2 V TA = -40°C to 125°C
Supply Current 10 20 µA
7 16 µA
RESET THRESHOLD VOLTAGE
ADM682_L
V
ADM682_M
V
ADM682_T
V
ADM682_S
V
ADM682_R
V
ADM682_Z
V
ADM682_Y
V
ADM682_W
ADM682_V
RESET THRESHOLD TEMPERATURE COEFFICIENT 60 ppm/°C
RESET THRESHOLD HYSTERESIS 10 mV
RESET TIMEOUT PERIOD 140 200 280 ms
VCC TO RESET DELAY 40 µs VTH − VCC = 100mV
RESET
Output Voltage
VOL 0.3 V V
0.3 V V
0.3 V VCC >=2.55V, I
0.4 V VCC>=4.25V, I
VOH 0.8 × VCC V V
0.8 × VCC V V
0.8 × VCC V V
RESET
Output leakage Current
RESET Output Voltage
VOL 0.3 V V
0.3 V V
0.4 V VCC >=4.75V, I
VOH 0.8 × VCC V V
0.8 × VCC V V
0.8 × VCC V V
0.8 × VCC V V
WATCHDOG INPUT (ADM6821/2/3/4)
Watchdog Timeout Period 1.12 1.6 2.40 s
= 1.53 V to 2.0 V for ADM682_W/V, TA = –40°C to +125°C, unless otherwise noted
CC
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
2.13 2.19 2.25 V
1.62 1.67 1.71 V
1.52 1.58 1.62 V
1 µA
WDI and MR unconnected,
V
=5.5V
CC
WDI and MR unconnected,
V
=3.6V
CC
>=1V, I
CC
>=1.2V, I
CC
>=1.8V, I
CC
>=3.15V, I
CC
>=4.75V, I
CC
RESET
>=1.8V, I
CC
>=3.15V, I
CC
> = 1V, I
CC
>=1.5V, I
CC
>=2.55V, I
CC
>=4.25V, I
CC
= 50µA
SINK
= 100µA
SINK
= 1.2mA
SINK
= 3.2mA
SINK
= 200µA
SOURCE
SOURCE
SOURCE
not asserted
= 500µA
SINK
= 1.2mA
SINK
= 3.2mA
SINK
= 1µA
SOURCE
= 100µA
SOURCE
SOURCE
SOURCE
= 500µA
= 800µA
= 500µA
= 800µA
Rev. PrB | Page 3 of 11
ADM6821–ADM6825 Preliminary Technical Data
Parameter Min Typ Max Unit Test Conditions/Comments
WDI Pulse Width 50 ns
WDI Input Threshold
VIL 0.3 × VCC V
VIH 0.7 × VCC V
WDI Input Current 120 160 µA V
−20 −15 µA V
MANUAL RESET INPUT (ADM6821/2/3/5)
MR
Input Threshold
0.3 × V
V
CC
0.7 × VCC V
MR
Input Pulse Width
MR
Glitch Rejection
MR
Pull-up Resistance
MR
to Reset Delay
1 µs
100 ns
25 52 75
k⍀
200 ns
V
= 0.4 V, V
IL
= VCC, time average
WDI
= 0, time average
WDI
= 0.8×V
IH
CC
Rev. PrB | Page 4 of 11
Loading...