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MAX6412UK34-T 中文资料
19-2336; Rev 2; 12/05
Low-Power, Single/Dual-Voltage ?P Reset Circuitswith Capacitor-Adjustable Reset
Timeout Delay
General Description
The MAX6412–MAX6420 low-power microprocessorsupervisor circuits monitor system
voltages from 1.6V to?Monitor System Voltages from 1.6V to 5V5V. These devices are
designed to assert a reset signal?Capacitor-Adjustable Reset Timeout Periodwhenever
the VCCsupply voltage or RESET IN falls belowits reset threshold or the manual reset
input is asserted.?Manual Reset Input (MAX6412/MAX6413/MAX6414)The reset output
remains asserted for the reset timeout?Adjustable Reset Input Optionperiod after
VCCand RESET IN rise above the reset(MAX6415–MAX6420)threshold and the manual reset
input is deasserted. Thereset timeout is externally set by a capacitor to
provide?Dual-Voltage Monitoring
more flexibility.
(MAX6418/MAX6419/MAX6420)The MAX6412/MAX6413/MAX6414 feature fixed thresholds?Low
Quiescent
Current
(1.7?A,
typ)from
1.http://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7575V
to
approximately
input.
100mV
increments
anda
MAX6415/MAX6416/MAX6417?3 RESET Output Options
manual
reset
5V
in
The
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are offered with an adjustable reset input that can monitorPush-Pull RESETvoltages
down to 1.26V and the MAX6418/MAX6419/Push-Pull RESETMAX6420 are offered with one
fixed input and oneOpen-Drain RESET
adjustable input to monitor dual-voltage systems.
?Guaranteed
Reset
Valid
to
VCC=
1VThe
MAX6412/MAX6415/MAX6418
have
an
active-low,push-pull reset output. The MAX6413/MAX6416/?Power-Supply Transient
ImmunityMAX6419 have an active-high, push-pull reset output?Small SOT23-5 Packages
and the MAX6414/MAX6417/MAX6420 have an active-low, open-drain reset output. All of
these devices are
offered in a SOT23-5 package and are fully specifiedfrom -40°C to
125°C.
Applications
AutomotiveMedical EquipmentIntelligent InstrumentsPortable Equipment
Battery-http://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7Powered
Computers/ControllersEmbedded ControllersCritical ?P MonitoringSet-Top BoxesNote:
The MAX6412/MAX6413/MAX6414 and MAX6418/Computers
MAX6419/MAX6420 are available with factory-set VCCresetthresholds from 1.575V to
5.0V in approximately 0.1V incre-ments. Insert the desired nominal reset threshold
suffix (fromTable 1) into the blanks following the letters UK. There are 33standard
versions with a required order increment of 2500pieces. Sample stock is generally
held on standard versions
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only (see Standard Versions Table). Required order increment is10,000 pieces for
nonstandard versions. Contact factory foravailability. All devices are available in
tape-and-reel
only.
Devices
are
available
in
both
leaded
and
lead-free
packaging.Specify lead-free by replacing “-T” with “ T” when ordering.Typical
Operating Circuit appears at end of data sheet.Selector Guide appears at end of data
sheet.
_____________http://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7_________
__________________________________________Maxim Integrated Products
1
For pricing, delivery, and ordering information,please contact Maxim/Dallas
Direct!at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX6412–MAX6420
with Capacitor-Adjustable Reset Timeout Delay
MAX6412–MAX6420
ABSOLUTE MAXIMUM RATINGS
All Voltages Referenced to GND
VCC........................................................................-0.3V
to
6.0VSRT, MR, RESET IN....................................-0.3V to (VCC
0.3V)RESET,
RESET(Push-Pull).........................-0.3V
to
0.3V)RESET(Open-Drain).............................................-0.3V
6.0VInput
Current
(VCC
to
(All
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Pins).....................................................±20mAOutput
Current
(RESET, RESET)......................................±20mA
Continuous
Power
Dissipation
(TA=
70°Chttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7)
5-Pin SOT23-5 (derate 7.1mW/°C above
70°C)........571mWOperating Temperature
Range.........................-40°C
to
125°CJunction
Temperature......................................................
Temperature Range.............................-65°C to
150°CStorage
150°CLead Temperature
(soldering, 10s)................................. 300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent
damage to the device. These are stress ratings only, and functionaloperation of the
device at these or any other conditions beyond those indicated in the operational
sections of the specifications is not implied. Exposure toabsolute maximum rating
conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC= 1V to 5.5V, TA= TMINto TMAX, unless otherwise specified. Typical values are
at VCC= 5V and TA=
25°C.) (Note 1)
2___________http://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7__________
__________________________________________________________________
with Capacitor-Adjustable Reset Timeout Delay
ELECTRICAL CHARACTERISTICS (continued)
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(VCC= 1V to 5.5V, TA= TMINto TMAX, unless otherwise specified. Typical values are
at VCC= 5V and TA=
25°C.) (Note 1)
Typical Operating Characteristics
(VCC= 5V, CSRT= 1500pF, TA =
25°C, unless otherwise noted.)
SUPPLY CURRENT vs.SUPPLY CURRENT vs.SUPPLY VOLTAGE
TEMPERATURE
RESET TIMEOUT PERIOD vs. CSRT
4
3.510,000
3
0cot 02-213.046)
sXA)
)
m1000
MA3
A(??2.5
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D((
TOINTNREEERRP100
R 2
R2.0TUUUCCO
UTUSS1.0E1
SER0.5
1
000.10
1
2
3
4
5
6
-50
-25
YYELL1.5MPPIPPT10
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25://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7
50
75
100
125
0.001
0.010.11101001000
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
CSRT (nF)
________________________________________________________________________________
_______3
MAX6412–MAX6420
with Capacitor-Adjustable Reset Timeout Delay
20
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(VCC= 5V, CSRT= 1500pF, TA =
25°C, unless otherwise noted.)
46XAM–2146XAM4RESET TIMEOUT PERIODRESET TIMEOUT PERIOD vs. TEMPERATURE
vs. TEMPERATURE
4.30600
550)
s)m4.25
s(? (500D ODIORIERP4.20
E450 PT UTOUEO400MEIMT4.15
I TT 350ETSEESRE4.10
R300250
4.05
200
-50
-25
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25
50
75
100
125
-50
-25
25
50
75100
125
TEMPERATURE (°C)
Thttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7EMPERATURE (°C)
RESET IN THRESHOLD VOLTAGE
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MAXIMUM TRANSIENT DURATIONvs. TEMPERATURE
vs. RESET THRESHOLD OVERDRIVE
1.2806
0175
cot 02-)2V
14( 6150E1.275XGA)
MsA?T(L
ON125V1.270OI
ATRET50SER1.255251.250
-50
-25
25
50
75
DTLAOR100HUS1.265D
ETRNHE75IT
SNNI1.260
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100
125
200
400
600
800
1000
TEMPERATURE (°C)RESET THRESHOLD OVERDRIVE (mV)
________________________________________________________________________________
_______
Low-Power, Single/Dual-Voltage ?P Reset Circuitswith Capacitor-Adjustable Reset
Timeout Delay
Pin Description
in a known state. The MAX6412–MAX6420 ?P supervi-The MAX6412–MAX6420 low-power
microprocessorsory
circuits
provide
the
reset
logic
code-(?P)http://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7
to
prevent
supervisory
circuits provide maximum adjustabilityexecution errors during power-up, power-down,
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andfor supply-voltage monitoring and reset functionality. Inbrownout conditions (see
Typical Operating Circuit). addition, the MAX6412–MAX6420 reset timeout periodFor
the MAX6413, MAX6416, and MAX6419, RESETis adjustable using an external capacitor.
changes from low to high whenever VCCor RESET INThe MAX6412/MAX6413/MAX6414 have
factory-drops below the reset threshold voltages. Once RESETtrimmed reset threshold
voltages in approximatelyIN and V100mV increments from 1.575V to 5.0V with a
manualage(s), RESET remains high for the reset timeout period,CCexceed their
respective
reset
threshold
volt-reset
input.
The
MAX6415/MAX6416/MAX6417
containthen goes low.
a reset threshold that can be adjusted to any voltageOn power-up, once Vabove 1.26V
using
external
resistors.
The
MAX6418/teed
to
be
a
logic
high.
For
applicationshttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7 requiring
validCCreaches 1V, RESET is guaran-MAX6419/MAX6420 offer both a factory-trimmed
resetreset logic when VCCis less than 1V, see the sectionthreshold and an adjustable
reset threshold input forEnsuring a Valid RESET/RESETOutput Down to VCC=
0.dual-voltage monitoring.
The active-low RESEToutput of the remaining supervi-A reset signal is asserted when
Vsors is the inverse of the MAX6413, MAX6416, andfalls below the preset values or
when CCand/or RESET INMRis asserted.MAX6419 active-high RESET output and is
guaranteedThe reset remains asserted for an externally pro-valid for VCC≥1V.
grammed
interval
after VCCand/or RESET IN
has risenabove the reset threshold or
MRis deasserted.
Reset Threshold
The MAX6415–MAX6420 monitor the voltage on RESETReset Output
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IN with an external resistor voltage-divider (Figure 1).
The
reset
output
is
typically
connected
to
the
resetinput
ohttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7f a ?P. A ?P’s reset
input starts or restarts the ?P
________________________________________________________________________________
_______5
MAX6412–MAX6420
with Capacitor-Adjustable Reset Timeout Delay
MAX6412–MAX6420
Use the following formula to calculate the externallymonitored voltage (VMON_TH):
VMON_TH= VRST?(R1
R2)/R2
where VMON_THis the desired reset threshold voltageand VRSTis the reset input
threshold (1.26V). ResistorsR1 and R2 can have very high values to minimize cur-rent
consumption due to low leakage currents. Set R2to some conveniently high value (1M?,
for example)and calculate R1 based on the desired monitored volt-age, using the
following formula:
R1 = R2 x (VMON_TH/VRST- 1) (?)
Manual Reset Input
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(MAX6412/MAX6413/MAX6414)
Many ?P based products require manual reset capabil-ity, allowing the operator, a
technicihttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7an, or external
logiccircuitry to initiate a reset. A logic low on MRassertsreset. Reset remains
asserted while MRis low and forthe reset timeout period after MRreturns high.
The MRhas an internal 20k?pullup resistor so it canbe left open if not used. Connect
a normally openmomentary switch from MRto ground to create a man-ual reset function
(external debounce circuitry is notrequired for long reset timeout periods).
A manual reset option can easily be implemented with theMAX6415–MAX6420 by
connecting a normally openmomentary switch in parallel with R2 (Figure 2). When
theswitch is closed, the voltage on RESET IN goes to zero,initiating a reset. Similar
to the MAX6412/MAX6413/MAX6414 manual reset, reset remains asserted while theswitch
is closed and for the reset timeout period after theswitch is opened.
MAX6415–MAX6420
Monitoring Voltages Other than VCC
(MAX6415/MAX6416/MAX6417)
://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7parThe
MAX6415/MAX6416/MAX6417 contain an adjustablereset threshold input. These devices
can be used tomonitor voltages other than VCC. Calculate VMON_THasshown in the Reset
Thresholdsection. (See Figure 3.)
Figure 1. Calculating the Monitored Threshold Voltage (VMON_TH)
6
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Figure 3. Monitoring External Voltages
________________________________________________________________________________
_______
with Capacitor-Adjustable Reset Timeout Delay
Dual-Voltage Monitoring
The reset delay time is set by a current/capacitor-con-(MAX6418/MAX6419/MAX6420)
trolled ramp compared to an internal 0.65V reference.The MAX6418/MAX6419/MAX6420
contain both facto-An internal 240nA ramp current source charges thery-trimmed
threshold voltages and an adjustable resetexternal capacitor. The charge to the
capacitor
isthreshold
input,
allowing
the
monitoring
of
two
voltages,clearedhttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7 when a
reset condition is detected. Once theVreset condition is removed, the voltage on the
capacitorwhen either of the voltages falls below its respectiveCCand VMON_TH(see
Figure 4). Reset is assertedramps according to the formula: dV/dt = I/C. The
Cthreshold voltage.
capacitor must ramp to 0.65V to deassert the reset.SRTApplication Information
CSRTmust be a low-leakage (
Selecting a Reset Capacitor
The reset timeout period is adjustable to accommodateOperating as a Voltage Detector
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a variety of ?P applications. Adjust the reset timeoutThe MAX6412–MAX6420 can be
operated in a voltageperiod (tdetector mode by floating the SRT pin. The reset delayRP)
by connecting a capacitor (CSRT and ground. Calculate the reset timeout capacitorSRT)
betweentimes for VCCrising above or falling below the thresholdas follows:
are
not
significantly
different.
The
reset
output
isdeasserted
smoothttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7hly without false
pulses.
CSRT= (tRP- 275?s) / (2.73 ?106)
where tRPis in seconds and CSRTis in Farads
________________________________________________________________________________
_______7
MAX6412–MAX6420
with Capacitor-Adjustable Reset Timeout Delay
MAX6412–MAX6420
impedance CMOS-logic inputs connected to RESETcan drift to undetermined voltages.
This presents noproblems in most applications, since most ?Ps andother circuitry do
not operate with VCCbelow 1V.
In those applications where RESETmust be valid downto 0, adding a pulldown resistor
between RESETandground sinks any stray leakage currents, holdingRESETlow (Figure 6).
The value of the pulldown resis-tor is not critical; 100k?is large enough not to
loadRESETand small enough to pull RESETto ground. Forapplications using the MAX6413,
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MAX6416,
andMAX6419,
a
100k?pullup
resistor
between
RESET
andVCCwill
http://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7hold RESET high when
VCCfalls below 1V(Figure 7). Open-drain RESETversions are not recom-mended for
applications requiring valid logic for VCCdown to 0.
Figure 5. MAX6414/MAX6417/MAX6420 Open-Drain RESET
Output Allows use with Multiple Supplies
Interfacing to Other Voltages for Logic
Compatibility
The open-drain outputs of the MAX6414/MAX6417/MAX6420 can be used to interface to ?Ps
with otherlogic levels.
As shown in Figure 5, the open-drain out-put can be connected
to voltages from 0 to 5.5V. Thisallows for easy logic compatibility to various
micro-processors.
In addition to issuing a reset to the ?P during power-up,power-down, and brownout
conditions,
these
supervisorsare
relatively
immune
to
short-duration
negative-goingtransients (glitches). The Maximum Transient Duration vs.Reset
Threshold Overdrive graph in the TypicalOperating Characteristicsshows this
relationship.://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7ar
The area below the curve of the graph is the region inwhich these devices typically
do not generate a resetpulse. This graph was generated using a negative-going pulse
applied to VCC, starting above the actualreset threshold (VTH) and ending below it
by the magni-tude indicated (reset-threshold overdrive). As the mag-nitude of the
transient decreases (farther below thereset threshold), the maximum allowable pulse
widthdecreases. Typically, a VCCtransient that goes 100mVbelow the reset threshold
and lasts 50?s or less will notcause a reset pulse to be issued.
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Negative-Going VCCTransients
Figure 6. Ensuring RESETValid to VCC
= 0
When VCCfalls below 1V, RESET/RESET current sink-ing (sourcing) capabilities decline
drastically. In thecase of the MAX6412, MAX6415, and MAX6418, high-8
Ensuring a Valid RESET or RESET
Down to VCC= 0
Figure
7.
Ensuring
RESET
Valid
to
Vhttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7CC = 0
________________________________________________________________________________
_______
with Capacitor-Adjustable Reset Timeout Delay
Layout Consideration
SRT is
a precise current source. When developing theTable 1. Reset Voltages Suffix
Table
layout for the application, be careful to minimize boardcapacitance and leakage
currents around this pin.Traces connected to SRT should be kept as short aspossible.
Traces carrying high-speed digital signalsand traces with large voltage potentials
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should be rout-ed as far from SRT as possible. Leakage current andstray capacitance
(e.g., a scope probe) at this pincould cause errors in the reset timeout period.
Whenevaluating these parts, use clean prototype boards toensure accurate reset
periods.
RESET IN is a high-impedance input, which is typicallydriven by a high-impedance
resistor-divider
network(e.g.,
1M?to
10M?).
Minimize
chttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7oupling to transient
sig-nals by keeping the connections to this input short. AnyDC leakage current at
RESET IN (e.g., a scope probe)causes errors in the programmed reset threshold.
TRANSISTOR COUNT: 325PROCESS: BiCMOS
________________________________________________________________________________
_______9
MAX6412–MAX6420
with Capacitor-Adjustable Reset Timeout Delay
MAX6412–MAX6420
Contact factory for availability of nonstandard versions.
10______________________________________________________________________________
________
with Capacitor-Adjustable Reset Timeout Delay
________________________________________________________________________________
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______11
MAX6412–MAX6420
with Capacitor-Adjustable Reset Timeout Delay
MAX6412–MAX6420
Package Information
(The
package
drawing(s)
in
this
data
sheet
may
nothttp://www.mianfeiwendang.com/doc/a29c7ebad2d87a9c1f77bad7 reflect the most
current specifications. For the latest package outline information,go to .)
SOT-23 5L .EP
S
Maxim cannot assume responsibility for use of any circuitry other than circuitry
entirely embodied in a Maxim product. No circuit patent licenses areimplied. Maxim
reserves the right to change the circuitry and specifications without notice at any
time.
12____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale,
CA
94086 408-737-7600?2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
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