Analog Devices ADM823 4 5 Datasheet

Supervisory Circuits with Watchdog and

FEATURES

Manual Reset in 5-Lead SC70 and SOT-23

ADM823/ADM824/ADM825

FUNCTIONAL BLOCK DIAGRAM

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)

V

CC

ADM823

V

REF

RESET

GENERATOR

V

CC

RESET

Push-pull output stages:

(ADM823)

RESET

, RESET (ADM824/ADM825)

RESET

MR

DEBOUNCE

WATCHDOG

DETECTOR

Low power consumption (5 µA)
Guaranteed reset output valid to V
Power supply glitch immunity
Specified over automotive temperature range
5-lead SC70 and SOT-23 packages

= 1 V

CC

GND WDI

Figure 1.

04534-0-001

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 push­button, through a manual reset input. The three parts feature

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.

different combinations of watchdog input, manual reset input
and output stage configuration, as shown in Table 1.

Table 1. Selection Table

Output Stage

Part No. Watchdog Timer Manual Reset

RESET

RESET

ADM823 Yes Yes Push-Pull –
ADM824 Yes – Push-Pull Push-Pull

ADM825 – Yes Push-Pull Push-Pull

Rev. 0

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ADM823/ADM824/ADM825

TABLE OF CONTENTS

Specifications..................................................................................... 3

Watch 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

10/04—Revision 0: Initial Version

Application Information................................................................ 10

Watch 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 Guides......................................................................... 11

Transie n t s ................................................ 10

CC

= 0 V........................................... 10

CC

Rev. 0 | Page 2 of 12

ADM823/ADM824/ADM825

SPECIFICATIONS

VCC = 4.75 V to 5.5 V for ADM82_L, VCC = 4.5 V to 5.5 V for ADM82_M, VCC = 3.15 V to 3.6 V for ADM82_T,

= 3 V to 3.6 V for ADM82_S, VCC = 2.7 V to 3.6 V for ADM82_R, VCC = 2.38 V to 2.75 V for ADM82_Z,

V

CC

V

= 2.25 V to 2.75 V for ADM82_Y, TA = T

CC

Table 2.

Parameter Min Typ Max Unit Test Conditions/Comments

SUPPLY

VCC Operating Voltage Range 1 5.5 V TA = 0°C to +70°C

1.2 V TA = T
Supply Current 10 24 µA

5 12 µA

RESET THRESHOLD VOLTAGE

ADM82_L

4.50 4.75 V TA = T
ADM82_M

4.25 4.50 V TA = T
ADM82_T

3.00 3.15 V TA = T
ADM82_S

2.85 3.00 V TA = T
ADM82_R

2.55 2.70 V TA = T
ADM82_Z (SC70 only)

2.25 2.38 V TA = T
ADM82_Y (SC70 only)

2.13 2.25 V TA = T
RESET THRESHOLD TEMPERATURE COEFFICIENT 40 ppm/°C
RESET THRESHOLD HYSTERESIS 10 mV ADM82_L/M
5 mV ADM82_T/S/R/Z/Y
RESET TIMEOUT PERIOD 140 200 280 ms
VCC TO RESET DELAY 40 µs VTH – VCC = 100 mV

RESET Output Voltage

0.3 V

0.3 V

V

0.8 × V

RESET Output Voltage 0.4 V

0.3 V

0.8 × V

MIN

to T

, unless otherwise noted.

MAX

WDI and
ADM82_L/M

WDI and
ADM82_T/S/R/Z/Y

4.56 4.63 4.70 V TA = 25°C

4.31 4.38 4.45 V TA = 25°C

3.04 3.08 3.11 V TA = 25°C

2.89 2.93 2.96 V TA = 25°C

2.59 2.63 2.66 V TA = 25°C

2.28 2.32 2.35 V TA = 25°C

2.16 2.19 2.22 V TA = 25°C

0.4 V

V

CC

ADM82_L/M
V

CC

ADM82_T/S/R/Z/Y

= 0°C to 70°C, VCC = 1 V,

T

A

V

CC

− 1.5 V

CC

V

CC

ADM82_L/M

V

CC

V

CC

ADM82_T/S/R/Z/Y
V

CC

ADM824L/M, ADM825L/M
V

CC

ADM824T/S/R/Z/Y,
ADM825T/S/R/Z/Y

V

CC

V

CC

to T

MIN

MAX

MR unconnected

MR unconnected

to T

MIN

MAX

to T

MIN

MAX

to T

MIN

MAX

to T

MIN

MAX

to T

MIN

MAX

to T

MIN

MAX

to T

MIN

MAX

= VTH min, I

= VTH min, I

falling, I

SINK

= VTH max, I

= VTH max, I

= VTH max, I

= VTH max, I

≥ 1.8 V, I

SOURCE

= 3.2 mA,

SINK

= 1.2 mA,

SINK

= 50 µA

= 120 µA,

SOURCE

= 30 µA,

SOURCE

= 3.2 mA,

SINK

= 1.2 mA,

SINK

= 150 µA

Rev. 0 | Page 3 of 12

ADM823/ADM824/ADM825

Parameter Min Typ Max Unit Test Conditions/Comments

WATCHDOG INPUT (ADM823, ADM824)

Watchdog Timeout Period 1.12 1.6 2.40 s
WDI Pulse Width 50 ns VIL = 0.4 V, V
WDI Input Threshold
V

IL

WDI Input Current 120 160 µA V

MANUAL RESET INPUT (ADM823, ADM825)

MR Input Threshold

0.7 × V
MR Input Pulse Width
MR Glitch Rejection
MR Pull-Up Resistance
MR to Reset Delay

0.7 × V

−20 −15 µA V

0.3 × V

0.3 × V

CC

V

CC

V

CC

V

CC

= VCC, time average

WDI

= 0, time average

WDI

= 0.8 × V

IH

CC

1 µs
100 ns
35 52 75 kΩ
500 ns

Rev. 0 | Page 4 of 12