AD ADM709TAN Power supply monitor with reset Datasheet

a
Power Supply Monitor
with Reset
ADM709
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
FUNCTIONAL BLOCK DIAGRAM
ADM709
VCC
RESET
GENERATOR
VTH
RESET
GND
APPLICATIONS
Microprocessor Systems
Computers
Controllers
Intelligent Instruments
Critical mP Monitoring
Automotive Systems
Critical mP Power Monitoring
VCC
VCC
ADM709
RESET
µP
RESET
GND
GENERAL DESCRIPTION
The ADM709 contains a power supply monitor which generates
a system reset during power-up, power-down and brownout
conditions. When VCC 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 VCC rises above the threshold. The RESET output remains operational with VCC 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
M
T
S
R
4.65
4.40
3.08
2.93
2.63
GND
Typical Operating Circuit
ORDERING GUIDE
Model
Reset
Threshold
Temperature
Range
Package
Option*
ADM709LAN
ADM709LAR
ADM709MAN
ADM709MAR
ADM709TAN
ADM709TAR
ADM709SAN
ADM709SAR
ADM709RAN
ADM709RAR
4.65 V
4.65 V
4.40 V
4.40 V
3.08 V
3.08 V
2.93 V
2.93 V
2.63 V
2.63 V
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
N-8
SO-8
N-8
SO-8
N-8
SO-8
N-8
SO-8
N-8
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.
© 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
ADM709–SPECIFICATIONS (V
CC
Parameter
Min
VCC Operating Voltage Range
1.0
1.2
Supply Current
Reset Threshold
4.5
4.25
3.00
2.85
2.55
VCC to RESET Delay
RESET Active Time-Out Period
= Full Operating Range, TA = TMIN to TMAX unless otherwise noted)
Typ
Max
Units
Test Conditions/Comments
35
35
65
65
5.5
5.5
85
110
150
200
V
V
µA
µA
µA
µA
TA = 0°C to +70°C
TA = –40°C to +85°C
VCC < 3.6 V, TA = 0°C to +70°C
VCC < 3.6 V, TA = –40°C to +85°C
VCC < 5.5 V, TA = 0°C to +70°C
VCC < 5.5 V, TA = –40°C to +85°C
4.65
4.40
3.08
2.93
2.63
4.75
4.50
3.15
3.00
2.70
V
V
V
V
V
ADM709L
ADM709M
ADM709T
ADM709S
ADM709R
µs
VCC = Reset Threshold max–min
380
ms
VCC = Reset Threshold max, VCC Rising
0.3
V
0.4
V
0.3
0.4
V
V
V
ADM709R/S/T, ISINK = 1.2 mA. VCC = Reset
Threshold min
ADM709L/M, ISINK = 3.2 mA. VCC = Reset
Threshold min
ISINK = 50 µA. VCC ≥ 1.0 V
ISINK = 100 µA. VCC ≥ 1.2 V
ADM709R/S/T, ISOURCE = 500 µA, VCC ≥ Reset
Threshold max
ADM709L/M, ISOURCE = 800 µA, VCC ≥ Reset
Threshold max
20
140
RESET Output Voltage
0.8 × VCC
280
VCC–1.5 V
V
Specifications subject to change without notice.
PIN FUNCTION DESCRIPTION
ABSOLUTE MAXIMUM RATINGS*
(TA = +25°C unless otherwise noted)
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +6 V
RESET Output . . . . . . . . . . . . . . . . . . . –0.3 V to VCC + 0.3 V
VCC Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 mA
RESET Output Current . . . . . . . . . . . . . . . . . . . . . . . . 20 mA
Power Dissipation, N-8 DIP . . . . . . . . . . . . . . . . . . . . 727 mW
θJA Thermal Impedance . . . . . . . . . . . . . . . . . . . . . 135°C/W
Power Dissipation, SO-8 SOIC . . . . . . . . . . . . . . . . . . 470 mW
θJA 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
*
Mnemonic Pin No.
Function
NC
1, 4, 5, 6, 8
No Connect Pins.
VCC
2
+5 V, +3.3 V, +3 V Power Supply
Input.
RESET
7
Logic Output. It remains low while
VCC is below the reset threshold
voltage and for 280 ms (typ) after
VCC rises above the threshold.
GND
3
Ground, 0 V.
PIN CONFIGURATION
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.
8
NC
VCC 2
ADM709
7
RESET
GND 3
TOP VIEW
(Not to Scale)
6
NC
5
NC
NC 1
NC 4
NC = NO CONNECT
–2–
REV. 0
ADM709
RESET at Voltages < 1 V
ADM709
VCC
RESET
GENERATOR
VTH
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.
RESET
GND
Figure 1. Functional Block Diagram
ADM709
RESET
VCC
VCC
ADM709
R1
GND
µP
RESET
RESET
GND
Figure 5. RESET Valid @ VCC < 1 V
GND
Glitch Immunity
The ADM709 is immune to short transients which may occur
on the VCC line. This is important so that spurious resets are not
generated as a result of minor glitches on the power supply.
Figure 2. Typical Operating Circuit
CIRCUIT INFORMATION
RESET Output
Additional glitch immunity may be obtained by connecting a
capacitor (0.1 µF or greater) as close as possible to the VCC pin
on the device.
RESET is an active low output which provides a reset signal to
the microprocessor whenever the VCC supply voltage is below
the reset threshold. An internal timer holds RESET low for
140 ms after the voltage on VCC 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 processor reset. On power-down, the RESET output remains low
with VCC as low as 1 V. This ensures that the microprocessor is
held in a stable shutdown condition as the power supply drops.
VCC
VRT
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.
+5V
VCC
VRT
ADM709
tRS
RESET
RESET
GND
Figure 3. Power Off/On RESET Timing
µP
RESET
GND
Figure 6. Interfacing to Microprocessors with
Bidirectional RESET
VCC
RESET
400ms/DIV
Figure 4. RESET Output vs. VCC
REV. 0
BUFFERED
RESET
–3–
ADM709
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8
C2022–18–4/95
8-Lead Plastic DIP
(N-8)
5
0.280 (7.11)
PIN 1
0.240 (6.10)
1
4
0.325 (8.25)
0.300 (7.62)
0.430 (10.92)
0.348 (8.84)
0.060 (1.52)
0.015 (0.38)
0.210
(5.33)
MAX
0.130
(3.30)
MIN
0.160 (4.06)
0.115 (2.93)
0.100
(2.54)
BSC
0.022 (0.558)
0.014 (0.356)
0.070 (1.77)
0.045 (1.15)
0.195 (4.95)
0.115 (2.93)
0.015 (0.381)
0.008 (0.204)
SEATING
PLANE
8-Lead SOIC
(SO-8)
5
8
0.1574 (4.00)
0.1497 (3.80)
PIN 1
0.2440 (6.20)
0.2284 (5.80)
4
1
0.1968 (5.00)
0.1890 (4.80)
0.0196 (0.50)
x 45 °
0.0099 (0.25)
0.0688 (1.75)
0.0532 (1.35)
0.0500
(1.27)
BSC
0.0192 (0.49)
0.0138 (0.35)
0.0098 (0.25)
0.0075 (0.19)
8°
0°
0.0500 (1.27)
0.0160 (0.41)
PRINTED IN U.S.A.
0.0098 (0.25)
0.0040 (0.10)
–4–
REV. 0
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