FUNCTIONAL BLOCK DIAGRAM
VCC
RESET
ADM709
VTH
RESET
GENERATOR
GND
RESET
ADM709
GND GND
µP
RESET
V
CC
V
CC
Typical Operating Circuit
ORDERING GUIDE
Reset Temperature Package
Model Threshold Range Option*
ADM709LAN 4.65 V –40°C to +85°C N-8
ADM709LAR 4.65 V –40°C to +85°C SO-8
ADM709MAN 4.40 V –40°C to +85°C N-8
ADM709MAR 4.40 V –40°C to +85°C SO-8
ADM709TAN 3.08 V –40°C to +85°C N-8
ADM709TAR 3.08 V –40°C to +85°C SO-8
ADM709SAN 2.93 V –40°C to +85°C N-8
ADM709SAR 2.93 V –40°C to +85°C SO-8
ADM709RAN 2.63 V –40°C to +85°C N-8
ADM709RAR 2.63 V –40°C to +85°C SO-8
*N = Plastic DIP; SO = SOIC.
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
a
Power Supply Monitor
with Reset
ADM709
© Analog Devices, Inc., 1995
One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A.
Tel: 617/329-4700 Fax: 617/326-8703
GENERAL DESCRIPTION
The ADM709 contains a power supply monitor which generates
a system reset during power-up, power-down and brownout
conditions. When V
CC
falls below the reset threshold, RESET
goes low and holds the µP in reset. On power-up the RESET
output is held low for 140 ms after V
CC
rises above the thresh-
old. The RESET output remains operational with V
CC
as low
as 1 V.
Three supply-voltage threshold levels are available suitable for
+5 V, +3.3 V and for +3 V supply monitoring. The actual reset
voltage threshold is given below.
The ADM709 is available in 8-pin DIP and SOIC packages.
Table I. Reset Threshold
Suffix Voltage (V)
L 4.65
M 4.40
T 3.08
S 2.93
R 2.63
FEATURES
Precision Supply Voltage Monitor
+5 V, +3.3 V, +3 V Power Supply Monitor
35 mA Quiescent Current
140 ms (min) Power-On Reset Pulse
Low Cost
8-Pin DIP/SO Packages
Upgrade for MAX709
APPLICATIONS
Microprocessor Systems
Computers
Controllers
Intelligent Instruments
Critical mP Monitoring
Automotive Systems
Critical mP Power Monitoring
REV. 0
–2–
(V
CC
= Full Operating Range, T
A
= T
MIN
to T
MAX
unless otherwise noted)
ABSOLUTE MAXIMUM RATINGS*
(T
A
= +25°C unless otherwise noted)
V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +6 V
RESET Output . . . . . . . . . . . . . . . . . . . –0.3 V to V
CC
+ 0.3 V
V
CC
Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 mA
RESET Output Current . . . . . . . . . . . . . . . . . . . . . . . . 20 mA
Power Dissipation, N-8 DIP . . . . . . . . . . . . . . . . . . . . 727 mW
θ
JA
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 135°C/W
Power Dissipation, SO-8 SOIC . . . . . . . . . . . . . . . . . . 470 mW
θ
JA
Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 110°C/W
Operating Temperature Range
Industrial ( A Version) . . . . . . . . . . . . . . . . . –40°C to +85°C
Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . . +300°C
Vapor Phase (60 secs) . . . . . . . . . . . . . . . . . . . . . . . . . +215°C
Infrared (15 secs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +220°C
Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C
ESD Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .>5 kV
*
Stresses above those listed under “Absolute Maximum Ratings” may cause
permanent damage to the device. This is a stress rating only and functional
operation of the device at these or any other conditions above those listed in the
operational sections of this specification is not implied. Exposure to absolute
maximum ratings for extended periods of time may affect device reliability.
PIN FUNCTION DESCRIPTION
Mnemonic Pin No. Function
NC 1, 4, 5, 6, 8 No Connect Pins.
V
CC
2 +5 V, +3.3 V, +3 V Power Supply
Input.
RESET 7 Logic Output. It remains low while
V
CC
is below the reset threshold
voltage and for 280 ms (typ) after
V
CC
rises above the threshold.
GND 3 Ground, 0 V.
ADM709–SPECIFICATIONS
Parameter Min Typ Max Units Test Conditions/Comments
V
CC
Operating Voltage Range 1.0 5.5 V T
A
= 0°C to +70°C
1.2 5.5 V T
A
= –40°C to +85°C
Supply Current 35 85 µAV
CC
< 3.6 V, T
A
= 0°C to +70°C
35 110 µAV
CC
< 3.6 V, T
A
= –40°C to +85°C
65 150 µAV
CC
< 5.5 V, T
A
= 0°C to +70°C
65 200 µAV
CC
< 5.5 V, T
A
= –40°C to +85°C
Reset Threshold 4.5 4.65 4.75 V ADM709L
4.25 4.40 4.50 V ADM709M
3.00 3.08 3.15 V ADM709T
2.85 2.93 3.00 V ADM709S
2.55 2.63 2.70 V ADM709R
V
CC
to RESET Delay 20 µsV
CC
= Reset Threshold max–min
RESET Active Time-Out Period 140 280 380 ms V
CC
= Reset Threshold max, V
CC
Rising
RESET Output Voltage 0.3 V ADM709R/S/T, I
SINK
= 1.2 mA. V
CC
= Reset
Threshold min
0.4 V ADM709L/M, I
SINK
= 3.2 mA. V
CC
= Reset
Threshold min
0.3 V I
SINK
= 50 µA. V
CC
≥ 1.0 V
0.4 V I
SINK
= 100 µA. V
CC
≥ 1.2 V
0.8 × V
CC
V ADM709R/S/T, I
SOURCE
= 500 µA, V
CC
≥ Reset
Threshold max
V
CC
–1.5 V V ADM709L/M, I
SOURCE
= 800 µA, V
CC
≥ Reset
Threshold max
Specifications subject to change without notice.
PIN CONFIGURATION
V
CC
RESET
1
2
3
4
8
7
6
5
TOP VIEW
(Not to Scale)
ADM709
NC
GND
NC
NC
NC
NC
NC = NO CONNECT
ADM709
REV. 0 –3–
RESET at Voltages < 1 V
The ADM709 RESET output is guaranteed to operate with
supply voltages as low as 1 V. If it is desired that the RESET
output remains low below 1 V, then a pull-down resistor should
be connected between the RESET output and GND. A resistor
of 100 kΩ is suitable. This is illustrated in Figure 5.
R1
RESET
ADM709
GND
Figure 5.
RESET
Valid @ V
CC
< 1 V
Glitch Immunity
The ADM709 is immune to short transients which may occur
on the V
CC
line. This is important so that spurious resets are not
generated as a result of minor glitches on the power supply.
Additional glitch immunity may be obtained by connecting a
capacitor (0.1 µF or greater) as close as possible to the V
CC
pin
on the device.
Microprocessors with Bidirectional I-O
Some microprocessors or microcontrollers such as the
MC68HC11 have bidirectional reset lines. In order to avoid
signal contention, a resistor of 4.7 kΩ should be connected
between the ADM709 RESET output and the microcontroller
RESET line. This arrangement is shown in Figure 6.
RESET
ADM709
GND GND
µP
BUFFERED
RESET
+5V
RESET
V
CC
Figure 6. Interfacing to Microprocessors with
Bidirectional
RESET
VCC
RESET
ADM709
VTH
RESET
GENERATOR
GND
Figure 1. Functional Block Diagram
RESET
ADM709
GND GND
µP
RESET
V
CC
V
CC
Figure 2. Typical Operating Circuit
CIRCUIT INFORMATION
RESET Output
RESET is an active low output which provides a reset signal to
the microprocessor whenever the V
CC
supply voltage is below
the reset threshold. An internal timer holds RESET low for
140 ms after the voltage on V
CC
rises above the threshold. This
is intended as a power-on reset signal for the processor. It allows
time for the power supply and microprocessor to stabilize after
power up. Similarly a power supply brownout will initiate a pro-
cessor reset. On power-down, the RESET output remains low
with V
CC
as low as 1 V. This ensures that the microprocessor is
held in a stable shutdown condition as the power supply drops.
VRT VRT
t
RS
V
CC
RESET
Figure 3. Power Off/On
RESET
Timing
V
CC
RESET
400ms/DIV
Figure 4.
RESET
Output vs. V
CC
REV. 0
–4–
ADM709
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Plastic DIP
(N-8)
PIN 1 0.280 (7.11)
0.240 (6.10)
4
58
1
SEATING
PLANE
0.060 (1.52)
0.015 (0.38)
0.130
(3.30)
MIN
0.210
(5.33)
MAX
0.160 (4.06)
0.115 (2.93)
0.430 (10.92)
0.348 (8.84)
0.022 (0.558)
0.014 (0.356) 0.070 (1.77)
0.045 (1.15)
0.100
(2.54)
BSC
0.325 (8.25)
0.300 (7.62)
0.015 (0.381)
0.008 (0.204)
0.195 (4.95)
0.115 (2.93)
8-Lead SOIC
(SO-8)
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8
°
0
°
0.0196 (0.50)
0.0099 (0.25) x 45
°
PIN 1
0.1574 (4.00)
0.1497 (3.80)
0.2440 (6.20)
0.2284 (5.80)
4
5
1
8
0.0192 (0.49)
0.0138 (0.35)
0.0500
(1.27)
BSC
0.0688 (1.75)
0.0532 (1.35)
0.0098 (0.25)
0.0040 (0.10)
0.1968 (5.00)
0.1890 (4.80)
PRINTED IN U.S.A. C2022–18–4/95
