ANALOG DEVICES ADM825 Service Manual

Supervisory Circuits with Watchdog and

Manual Reset in 5-Lead SC70 and SOT-23

FEATURES

Precision 2.5 V to 5 V power supply monitor
7 reset threshold options: 2.19 V to 4.63 V
140 ms (minimum) reset timeout
Watchdog timer with 1.6 sec timeout (ADM823, ADM824)
Manual reset input (ADM823, ADM825)
Push-pull output stages

(ADM823)

RESET

, RESET (ADM824/ADM825)

RESET
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

APPLICATIONS

Microprocessor systems
Computers
Controllers
Intelligent instruments
Portable equipment

= 1 V

CC

ADM823/ADM824/ADM825

FUNCTIONAL BLOCK DIAGRAM

ADM823

V

MR

CC

V

REF

DEBOUNCE

GND WDI

RESET

GENERATOR

WATCHDOG

DETECTOR

Figure 1.

V

CC

RESET

04534-001

GENERAL DESCRIPTION

The ADM823/ADM824/ADM825 are supervisory circuits that
monitor power supply voltage levels and code execution integrity
in microprocessor-based systems. In addition to 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
different combinations of watchdog input, manual reset input,
and output stage configuration, as shown in Tab le 1 .

Table 1. Selection Table

Part No. Watchdog Timer Manual Reset
ADM823 Yes Yes Push-Pull –
ADM824 Yes – Push-Pull Push-Pull
ADM825 – Yes Push-Pull Push-Pull

These parts are 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 (minimum) and 1.6 sec
(typical), respectively.

The ADM823/ADM824/ADM825 are available in 5-lead SC70
and SOT-23 packages and typically consume only 5 µA, making
them suitable for use in low power, portable applications.

Output Stage

RESET

RESET

Rev. C

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ADM823/ADM824/ADM825

TABLE OF CONTENTS

Features.............................................................................................. 1

Applications....................................................................................... 1

Functional Block Diagram .............................................................. 1

General Description ......................................................................... 1

Revision History ............................................................................... 2

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

Absolute Maximum Ratings............................................................ 5

ESD Caution.................................................................................. 5

Pin Configurations and Function Descriptions ........................... 6

Typical Performance Characteristics ............................................. 7

Circuit Description........................................................................... 9

REVISION HISTORY

10/10—Rev. B to Rev. C

Updated Outline Dimensions....................................................... 11

Changes to Ordering Guide.......................................................... 11

5/08—Rev. A to Rev. B

Changes to General Description Section ...................................... 1

Changes to Table 4............................................................................ 6

Changes to Ordering Guide.......................................................... 11

2/07—Rev. 0 to Rev. A

Updated Format..................................................................Universal

Changes to Ordering Guide.......................................................... 11

10/04—Revision 0: Initial Version

Reset Output ..................................................................................9

Manual Reset Input.......................................................................9

Watchdog Input.............................................................................9

Applications Information.............................................................. 10

Watchdog Input Current........................................................... 10

Negative-Going VCC Transients................................................ 10

Ensuring Reset Valid to VCC = 0 V........................................... 10

Watchdog Software Considerations......................................... 10

Outline Dimensions....................................................................... 11

Ordering Guide .......................................................................... 11

Rev. C | Page 2 of 12

ADM823/ADM824/ADM825

SPECIFICATIONS

VCC = 4.75 V to 5.5 V for ADM82xL, VCC = 4.5 V to 5.5 V for ADM82xM, VCC = 3.15 V to 3.6 V for ADM82xT, VCC = 3 V to 3.6 V
for ADM82xS, V
T

= T

MIN

to T

A

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

ADM82xL

4.50 4.75 V TA = T

ADM82xM

4.25 4.50 V TA = T

ADM82xT

3.00 3.15 V TA = T

ADM82xS

2.85 3.00 V TA = T

ADM82xR

2.55 2.70 V TA = T

ADM82xZ (SC70 Only)

2.25 2.38 V TA = T

ADM82xY (SC70 Only)

2.13 2.25 V TA = T
RESET THRESHOLD TEMPERATURE COEFFICIENT 40 ppm/°C
RESET THRESHOLD HYSTERESIS 10 mV ADM82xL/M
5 mV ADM82xT/S/R/Z/Y
RESET TIMEOUT PERIOD 140 200 280 ms
VCC TO RESET DELAY 40 μs VTH − VCC = 100 mV

RESET/RESET

RESET Output Voltage

0.3 V

0.3 V

V

0.8 × VCC V

RESET Output Voltage (ADM824, ADM825) 0.4 V

0.3 V

0.8 × VCC V V

= 2.7 V to 3.6 V for ADM82xR, VCC = 2.38 V to 2.75 V for ADM82xZ, VCC = 2.25 V to 2.75 V for ADM82xY,

CC

, unless otherwise noted.

MAX

to T

MIN

MAX

WDI and MR

unconnected

ADM82xL/M
WDI and MR

unconnected

ADM82xT/S/R/Z/Y

4.56 4.63 4.70 V TA = 25°C
to T

MIN

4.31 4.38 4.45 V TA = 25°C
to T

MIN

3.04 3.08 3.11 V TA = 25°C
to T

MIN

2.89 2.93 2.96 V TA = 25°C
to T

MIN

2.59 2.63 2.66 V TA = 25°C
to T

MIN

2.28 2.32 2.35 V TA = 25°C
to T

MIN

2.16 2.19 2.22 V TA = 25°C
to T

MIN

MAX

MAX

MAX

MAX

MAX

MAX

MAX

0.4 V

VCC = VTH min, I
ADM82xL/M

= VTH min, I

V

CC

ADM82xT/S/R/Z/Y

= 0°C to 70°C, VCC = 1 V,

T

A

V

falling, I

− 1.5 V

CC

CC

= VTH max, I

V

CC

SINK

ADM82xL/M

= VTH max, I

V

CC

ADM82xT/S/R/Z/Y

= VTH max, I

V

CC

ADM82xL/M

= VTH max, I

V

CC

ADM82xT/S/R/Z/Y

≥ 1.8 V, I

CC

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. C | 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 sec
WDI Pulse Width 50 ns VIL = 0.4 V, VIH = 0.8 × VCC
WDI Input Threshold, VIL 0.7 × VCC 0.3 × VCC V
WDI Input Current 120 160 μA V

MANUAL RESET INPUT (ADM823, ADM825)

MR Input Threshold
MR Input Pulse Width
MR Glitch Rejection
MR Pull-Up Resistance
MR to Reset Delay

= VCC, time average

WDI

−20 −15 μA V

0.7 × V

0.3 × VCC V

CC

= 0 V, time average

WDI

1 μs
100 ns
35 52 75 kΩ
500 ns

Rev. C | Page 4 of 12