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3 V, Voltage Monitoring
Microprocessor Supervisory Circuits
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
FEATURES
Precision supply voltage monitor
2.63 V (ADM706P, ADM706R, ADM708R)
2.93 V (ADM706S, ADM708S)
3.08 V (ADM706T, ADM708T)
100 μA quiescent current
200 ms reset pulse width
Debounced manual reset input (MR)
Independent watchdog timer
1.6 second timeout (ADM706x)
Reset output
Active high (ADM706P)
Active low (ADM706R, ADM706S, ADM706T)
Both active high and active low (ADM708R, ADM708S,
ADM708T)
Voltage monitor for power-fail or low battery warning
Guaranteed RESET valid with V
CC
= 1 V
Superior upgrade for MAX706P/R/S/T, MAX708R/S/T
WATCHDOG
INPUT (WDI)
FUNCTIONAL BLOCK DIAGRAMS
WATCHDOG
TRANSITION
DETECTOR
V
CC
70μA
MR
V
CC
V
REF
*
POWER-FAIL
INPUT (PFI)
1.25V
WATCHDOG
TIMER
WATCHDOG
OUTPUT (WDO)
RESET AND
WATCHDOG
TIMEBASE
RESET
GENERATOR
RESET,
(P = RESET)
ADM706P/ADM706R/
ADM706S/ADM706T
POWER-FAIL
OUTPUT (PFO)
06435-001
* VOLTAGE REFERENCE = 2.63V (P/R), 2.93V (S), 3.08V (T)
Figure 1. ADM706P/ADM706R/ADM706S/ADM706T
V
CC
70μA
MR
RESET
GENERATOR
V
REF
*
POWER-FAIL
INPUT (PFI)
1.25V
* VOLTAGE REFERENCE = 2.63V (R), 2.93V (S), 3.08V (T)
RESET
RESET
APPLICATIONS
Microprocessor systems
Computers
Controllers
Intelligent instruments
Critical microprocessor monitoring
Battery-operated systems
Portable instruments
V
CC
ADM708R/ADM708S/
ADM708T
06435-002
POWER-FAIL
OUTPUT (PFO)
Figure 2. ADM708R/ADM708S/ADM708T
GENERAL DESCRIPTION
The ADM706P/ADM706R/ADM706S/ADM706T and the
ADM708R/ADM708S/ADM708T microprocessor supervisory
circuits are suitable for monitoring either 3 V or 3.3 V power
supplies.
The ADM706P/ADM706R/ADM706S/ADM706T provide
power-supply monitoring circuitry that generate a reset output
during power-up, power-down, and brownout conditions. The
reset output remains operational with V
CC
as low as 1 V.
Independent watchdog monitoring circuitry is also provided.
This is activated if the watchdog input has not been toggled
within 1.6 seconds.
In addition, there is a 1.25 V threshold detector for power-fail
warning, low battery detection, or to monitor an additional power
supply. An active low debounced MR input is also included.
The ADM706R, ADM706S, and ADM706T are identical except
for the reset threshold monitor levels, which are 2.63 V, 2.93 V, and
3.08 V, respectively. The ADM706P is identical to the ADM706R in
that the reset threshold is 2.63 V. It differs only in that it has an
active high reset output.
The ADM708R/ADM708S/ADM708T provide similar functio-
nality as the ADM706R/ADM706S/ADM706T and only differ
in that a watchdog timer function is not available. Instead, an
active high reset output (RESET) is provided in addition to the
active low (RESET) output.
All parts are available in narrow 8-lead PDIP and 8-lead SOIC
packages.
Rev. C
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: 781.461.3113 ©1995–2008 Analog Devices, Inc. All rights reserved.
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
Functional Block Diagrams ............................................................. 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 ............................................. 8
Circuit Information ........................................................................ 10
Power-Fail Reset ......................................................................... 10
Manual Reset............................................................................... 10
Watchdog Timer (ADM706x) .................................................. 10
Power-Fail Comparator ............................................................. 11
Adding Hysteresis to the Power-Fail Comparator ................. 11
Valid RESET Below 1 V V
CC
..................................................... 11
Applications Information .............................................................. 12
Monitoring Additional Supply Levels...................................... 12
Microprocessors with Bidirectional RESET ........................... 12
Outline Dimensions ....................................................................... 13
Ordering Guide .......................................................................... 14
REVISION HISTORY
5/08—Rev. B to Rev. C
Changes to Applications Section .................................................... 1
Changes to Table 2 ............................................................................ 5
Changes to Table 3 ............................................................................ 6
Changes to Figure 8 .......................................................................... 7
Changes to Figure 16 ........................................................................ 9
2/07—Rev. A to Rev. B
Updated Format .................................................................. Universal
Changes to Table 1 ............................................................................ 3
Updated Outline Dimensions ....................................................... 12
Changes to Ordering Guide .......................................................... 13
Rev. C | Page 2 of 16
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
SPECIFICATIONS
V
CC
= 2.70 V to 5.5 V (ADM706P/ADM70xR), V
CC
= 3.00 V to 5.5 V (ADM70xS), V
CC
= 3.15 V to 5.5 V (ADM70xT), T
A
= T
MIN
to T
MAX
unless otherwise noted.
Table 1.
Parameter
POWER SUPPLY
V
CC
Operating Voltage Range
Supply Current
LOGIC OUTPUT
Reset Threshold (V
RST
)
Min
1.0
100
150
2.55
2.85
3.00
160
160
2.63
2.93
3.08
20
200
200
200
Typ
Max
5.5
200
350
2.70
3.00
3.15
280
280
Unit
V
μA
μA
V
V
V
mV
ms
ms
ms
Test Conditions/Comments
V
CC
< 3.6 V
V
CC
< 5.5 V
ADM706P/ADM70xR
ADM70xS
ADM70xT
ADM706P/ADM70xR, V
CC
= 3 V
ADM70xS/ADM70xT, V
CC
= 3.3 V
V
CC
= 5.0 V
Reset Threshold Hysteresis
RESET PULSE WIDTH
RESET OUTPUT VOLTAGE
(ADM70xR/ADM70xS/ADM70xT)
V
OH
V
OL
V
OH
V
OL
V
OL
RESET OUTPUT VOLTAGE (ADM706P)
V
OH
V
OL
V
OH
V
OL
RESET OUTPUT VOLTAGE (ADM708x)
V
OH
V
OL
V
OH
V
OL
WATCHDOG INPUT (ADM706x)
Watchdog Timeout Period
0.8 × V
CC
0.3
V
CC
− 1.5 V
0.4
0.3
V
CC
− 0.6 V
0.3
V
CC
− 1.5 V
0.4
0.8 × V
CC
0.3
V
CC
− 1.5 V
0.4
1.00
1.60
2.25
V
V
V
V
V
V
V
V
V
V
V
V
V
sec
V
RST
(max) < V
CC
< 3.6 V, I
SOURCE
= 500 μA
V
RST
(max) < V
CC
< 3.6 V, I
SINK
= 1.2 mA
4.5 V < V
CC
< 5.5 V, I
SOURCE
= 800 μA
4.5 V < V
CC
< 5.5 V, I
SINK
= 3.2 mA
V
CC
= 1 V, I
SINK
= 100 μA
V
RST
(max) < V
CC
< 3.6 V, I
SOURCE
= 215 μA
V
RST
(max) < V
CC
< 3.6 V, I
SINK
= 1.2 mA
4.5 V < V
CC
< 5.5 V, I
SOURCE
= 800 μA
4.5 V < V
CC
< 5.5 V, I
SINK
= 3.2 mA
V
RST
(max) < V
CC
< 3.6 V, I
SOURCE
= 500 μA
V
RST
(max) < V
CC
< 3.6 V, I
SINK
= 500 μA
4.5 V < V
CC
< 5.5 V, I
SOURCE
= 800 μA
4.5 V < V
CC
< 5.5 V, I
SINK
= 1.2 mA
ADM706P/ADM706R: V
CC
= 3 V;
ADM706S/ADM706T: V
CC
= 3.3 V;
V
IL
= 0.4 V, V
IH
= V
CC
× 0.8 V
V
RST
(max) < V
CC
< 3.6 V
4.5 V < V
CC
< 5.5 V
V
RST
(max) < V
CC
< 3.6 V
V
RST
(max) < V
CC
< 3.6 V
V
CC
= 5.0 V
V
CC
= 5.0 V
WDI = 0 V or V
CC
V
RST
(max) < V
CC
< 3.6 V, I
SOURCE
= 500 μA
4.5 V < V
CC
< 5.5 V, I
SOURCE
= 800 μA
V
RST
(max) < V
CC
< 3.6 V, I
SINK
= 500 μA
4.5 V < V
CC
< 5.5 V, I
SINK
= 1.2 mA
WDI Pulse Width
WDI Input Threshold
V
IL
V
IH
V
IL
V
IH
WDI Input Current
WDO OUTPUT VOLTAGE
V
OH
V
OL
100
50
0.6
0.7 × V
CC
0.8
3.5
−1.0
0.8 × V
CC
V
CC
− 1.5 V
0.3
0.4
+0.02
+1.0
ns
ns
V
V
V
V
μA
V
V
V
V
Rev. C | Page 3 of 16
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
Parameter
MANUAL RESET INPUT
MR Pull-Up Current (MR = 0 V)
MR Pulse Width
MR INPUT THRESHOLD
V
IL
V
IH
V
IL
V
IH
MR TO RESET OUTPUT DELAY
POWER-FAIL INPUT
PFI Input Threshold
PFI Input Current
PFO OUTPUT VOLTAGE
V
OH
V
OL
V
OH
V
OL
Min
25
100
500
150
Typ
70
250
Max
250
600
Unit
μA
μA
ns
ns
V
V
V
V
ns
ns
V
nA
V
V
V
V
V
RST
(max) < V
CC
< 3.6 V, I
SOURCE
= 500 μA
V
RST
(max) < V
CC
< 3.6 V, I
SINK
= 1.2 mA
4.5 V < V
CC
< 5.5 V, I
SOURCE
= 800 μA
4.5 V < V
CC
< 5.5 V, I
SINK
= 3.2 mA
Test Conditions/Comments
V
RST
(max) < V
CC
< 3.6 V
4.5 V < V
CC
< 5.5 V
V
RST
(max) < V
CC
< 3.6 V
4.5 V < V
CC
< 5.5 V
V
RST
(max) < V
CC
< 3.6 V
V
RST
(max) < V
CC
< 3.6 V
4.5 V < V
CC
< 5.5 V
4.5 V < V
CC
< 5.5 V
V
RST
(max) < V
CC
< 3.6 V
4.5 V < V
CC
< 5.5 V
ADM70xP/ADM70xR, V
CC
= 3 V
ADM70xS/ADM70xT, V
CC
= 3.3 V, PFI falling
0.6
0.7 × V
CC
0.8
2.0
750
250
1.2
−25
0.8 × V
CC
0.3
V
CC
− 1.5 V
0.4
1.25
+0.01
1.3
+25
Rev. C | Page 4 of 16
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