MAX709LCPA ,Power-Supply Monitor with ResetFeaturesThe MAX709 provides a system reset during power-up, ' +5V, +3.3V, and +3V Versionspower-dow ..
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MAX709LCSA ,Power-Supply Monitor with ResetFeaturesThe MAX709 provides a system reset during power-up, ' +5V, +3.3V, and +3V Versionspower-dow ..
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MAX709LCSA ,Power-Supply Monitor with ResetGeneral Description _______
MAX709LCSA+ ,Power-Supply Monitor with ResetMAX70919-0136; Rev. 2; 12/05Power-Supply Monitor with Reset_______________
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MB4752A ,SUBSCRIBER LINE INTERFACE IC" mm;
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MAX709LCPA-MAX709LCSA-MAX709LESA-MAX709MCSA-MAX709MESA-MAX709RCSA-MAX709RESA-MAX709SCSA-MAX709SCUA-MAX709SESA-MAX709TCSA-MAX709TEPA-MAX709TESA
Power-Supply Monitor with Reset
MAX709
Power-Supply Monitor with Reset
________________________________________________________________Maxim Integrated Products1
__________________Pin Configuration
__________Typical Operating Circuit
Call toll free 1-800-998-8800 for free samples or literature.19-0136; Rev. 1; 6/94
_______________General DescriptionThe MAX709 provides a system reset during power-up,
power-down, and brownout conditions. When VCCfalls
below the reset threshold, RESETgoes low and holds
the µP in reset for 140ms min after VCCrises above the
threshold.
The RESEToutput is guaranteed to be in the correct
state with VCCdown to 1V. The MAX709 provides
excellent circuit reliability and low cost by eliminating
external components and adjustments when used with
+5V, +3.3V, or +3V powered systems. The MAX709 is
available 8-pin DIP, µMAX, and SO packages.
_______________________ApplicationsMinimum Component Count,
Low-Cost Processor Systems
___________________________Features+5V, +3.3V, and +3V VersionsNo External ComponentsLow CostPrecise Power-Down Reset Threshold140ms Min Power-On Reset DelayImmune to Short Negative VCCTransients8-Pin DIP, µMAX, and SO PackagesLow Supply Current: 35µA - MAX709R/S/T
65µA - MAX709L/M
______________Ordering Information* Dice are specified at TA= +25°C,DCparameters only.
Note:This part offers a choice of five different reset threshold
voltages. Select the letter corresponding to the desired
nominal reset threshold voltage, and insert it into the
blank to complete the part number.
MAX709
Power-Supply Monitor with Reset_______________________________________________________________________________________Terminal Voltage (with respect to GND)
VCC................................................-0.3V to 6.0V
RESET....................................-0.3V to (VCC+ 0.3V)
Input Current, VCC..........................................20mA
Output Current, RESET.....................................20mA
Rate-of-Rise, VCC.........................................100V/µs
Continuous Power Dissipation (TA= +70°C)
Plastic DIP (derate 9.09mW/°C above +70°C)........727mW
µMAX (derate 4.10mW/°C above +70°C).............330mW
SO (derate 5.88mW/°C above +70°C).................471mW
Operating Temperature Ranges
MAX709_C___ ...................................0°C to +70°C
MAX709_E___ .................................-40°C to +85°C
Storage Temperature Range ..................-65°C to +160°C
Lead Temperature (soldering, 10sec)....................+300°C
ELECTRICAL CHARACTERISTICS(VCC= full range, TA= TMINto TMAX, unless otherwise noted.)
Stresses beyond those listed under “Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Note 1:Supply current is measured with VCC= 3.6V for MAX709R/S/T, and VCC= 5.5V for all versions.
ABSOLUTE MAXIMUM RATINGS
MAX709
Power-Supply Monitor with Reset
_________________________________________________________________________________________________3POWER-UP RESET DELAY
vs. TEMPERATURE
TEMPERATURE (°C)
POWER-UP RESET DELAY (ms)
SUPPLY CURRENT
vs. TEMPERATURE
TEMPERATURE (°C)
SUPPLY CURRENT (
POWER-DOWN RESET DELAY
vs. TEMPERATURE
TEMPERATURE (°C)
POWER-DOWN RESET DELAY (
__________________________________________Typical Operating Characteristics
NORMALIZED RESET THRESHOLD
vs. TEMPERATURE
TEMPERATURE (°C)
NORMALIZED RESET THRESHOLD
0.995
MAX709
Power-Supply Monitor with Reset_______________________________________________________________________________________
__________Applications Information
Negative-Going VCCTransientsIn addition to issuing a reset to the microprocessor
(µP) during power-up, power-down, and brownout con-
ditions, the MAX709 is relatively immune to short dura-
tion negative-going VCCtransients (glitches).
Figure 1 shows typical transient duration vs. reset com-
parator overdrive, for which the MAX709 does not gen-
erate a reset pulse. The graph was generated using a
negative-going pulse applied to VCC, starting 1.5V
above the actual reset threshold and ending below it
by the magnitude indicated (reset comparator over-
drive). The graph indicates the typical maximum pulse
width that a negative-going VCCtransient may have
without causing a reset pulse to be issued. As the
magnitude of the transient increases (goes farther
below the reset threshold), the maximum allowable
pulse width decreases. Typically, for the
MAX709L/MAX709M, a VCCtransient that goes 100mV
below the reset threshold and lasts 40µs or less will not
cause a reset pulse to be issued.
A 0.1µF bypass capacitor mounted as close as possible
to pin 2 (VCC) provides additional transient immunity.
Ensuring a Valid RESETOutput
Down to VCC= 0VWhen VCCfalls below 1V, the MAX709 RESEToutput
no longer sinks current—it becomes an open circuit.
Therefore, high-impedance CMOS logic inputs con-
nected to the RESEToutput can drift to undermined
voltages. This presents no problem in most applica-
tions, since most µP and other circuitry is inoperative
with VCCbelow 1V. However, in applications where the
RESEToutput must be valid down to 0V, adding a pull-
down resistor to the RESETpin will cause any stray
leakage currents to flow to ground, holding RESETlow
(see Figure 2). The resistance value of R1 is not criti-
cal. It should be about 100kΩ, which is large enough
not to load RESETand small enough to pull RESETto
ground.
____________________Pin DescriptionFigure 1.Maximum Transient Duration without Causing a
Reset Pulse vs. Reset Comparator Overdrive
MAX709
Power-Supply Monitor with Reset
_______________________________________________________________________________________5
Interfacing to µPs with
Bidirectional Reset PinsMicroprocessors with bidirectional reset pins (such as
the Motorola 68HC11 series) can contend with the
MAX709 reset output. If, for example the MAX709
RESEToutput is asserted high and the µP wants to pull
it low, indeterminate logic levels may result. To correct
this, connect a 4.7kΩresistor between the MAX709
RESEToutput and the µP reset I/O (see Figure 3).
Buffer the MAX709 RESEToutput to other system com-
ponents.
Figure 2.RESETValid to VCC= Ground Circuit
Figure 3.Interfacing to µPs with Bidirectional Reset I/O
MAX709
Power-Supply Monitor with Reset
