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ADM709LAN-ADM709LAR-ADM709MAR-ADM709RAR-ADM709SAN-ADM709TAR
Power Supply Monitor with Reset
FUNCTIONAL BLOCK DIAGRAM
VCC
RESET
GNDTypical Operating Circuit
ORDERING GUIDE*N = Plastic DIP; SO = SOIC.
REV.0
Power Supply Monitor
with Reset
GENERAL DESCRIPTIONThe 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 thresh-
old. 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
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
(VCC = Full Operating Range, TA = TMIN to TMAX unless otherwise noted)
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
*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
ADM709–SPECIFICATIONSSpecifications subject to change without notice.
PIN CONFIGURATION
VCCRESET
GND
NC = NO CONNECT
RESET at Voltages < 1 VThe 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.
Figure 5.RESET Valid @ VCC < 1 V
Glitch ImmunityThe 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.
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.
Microprocessors with Bidirectional I-OSome 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.
Figure 6.Interfacing to Microprocessors with
Bidirectional RESET
VCC
RESET
GNDFigure 1.Functional Block Diagram
Figure 2.Typical Operating Circuit
CIRCUIT INFORMATION
RESET OutputRESET 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 pro-
cessor 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
RESETFigure 3.Power Off/On RESET Timing
VCC
RESET
400ms/DIVFigure 4.RESET Output vs. VCC
ADM709
OUTLINE DIMENSIONSDimensions shown in inches and (mm).
8-Lead Plastic DIP
(N-8)
8-Lead SOIC
(SO-8)PRINTED IN U.S.A.
C2022–18–4/95
:
www.ic-phoenix.com
.
