Download MAX6340UK16-T中文资料

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MAX6340UK16-T 中文资料
19-2440; Rev 4; 12/05
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
General Description
Features
The MAX6340/MAX6421–MAX6426 low-power micro-processor supervisor circuits monitor
system voltages?Monitor System Voltages from 1.6V to 5Vfrom 1.6V to 5V. These devices
perform a single function:?Capacitor-Adjustable Reset Timeout Periodthey assert a
reset signal whenever the VCCsupply volt-age falls below its reset threshold. The
reset output?Low Quiescent Current (1.6?A typ)remains asserted for the reset timeout
period after V?Three RESET Output Options
rises above the reset threshold. The reset timeout is exter-CCPush-Pull RESETnally
set by a capacitor to provide more flexibility.Push-Pull RESETThe MAX6421/MAX6424
have an active-low, push-Open-Drain RESETpull reset output. The MAX6422 has an
active-high,push-pull reset output and the MAX6340/MAX6423/?Guaranteed Reset Valid
to
VCC=
1VMAX6425/MAX6426
have
an
ahttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.htmlctive-low,
open-drain?Immune to Short VCCTransients
reset output. The MAX6421/MAX6422/MAX6423 areoffered in 4-pin SC70 or SOT143 packages.
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The?Small 4-Pin SC70, 4-Pin SOT143, and 5-Pin SOT23MAX6340/MAX6424/MAX6425/MAX6426
are availablePackagesin 5-pin SOT23-5 packages.
?MAX6340
Pin
Compatible
with
LP3470?MAX6424/MAX6425
Pin
Compatible
withNCP300–NCP303, MC33464/MC33465,S807/S808/S809, and RN5VDPortable Equipment
?MAX6426 Pin Compatible with PST92XX
Battery-Powered Computers/ControllersOrdering Information
AutomotiveMedical EquipmentIntelligent InstrumentsEmbedded ControllersCritical ?P
MonitoringSet-Top BoxesComputers
Typical Operating Circuit appears at end of data sheet.
Note: The MAX6340/MAX6421–MAX6426 are available with fac-tory-trimmed reset
thresholds from 1.575V to 5.0V in approxi-mately 0.1V increments. Insert the desired
nominal
resetthreshold
suffix
(frohttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.htmlm Table 1) into
the blanks. There are 50 stan-dard versions with a required order increment of 2500
pieces.Sample stock is generally held on standard versions only (seeStandard Versions
Table). Required order increment is 10,000pieces for nonstandard versions. Contact
factory for availability.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.Selector Guide appears at end of data sheet.
________________________________________________________________Maxim Integrated
Products
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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.
MAX6340/MAX6421–MAX6426
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
MAX6340/MAXhttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.html6421–MAX
6426
ABSOLUTE MAXIMUM RATINGS
All Voltages Referenced to GND
VCC........................................................................-0.3V
to
6.0VSRT,
0.3V)RESET(open
RESET,
RESET
(push-pull).................-0.3V
to
drain)...............................................-0.3V
6.0VInput
Current
pins)......................................................±20mAOutput
(VCC
to
(all
Current
(RESET, RESET)......................................±20mA
Continuous Power Dissipation (TA=
70°C)
4-Pin SC70 (derate 3.1mW/°C above
70°C)..............245mW4-Pin SOT143 (derate
4mW/°C above
70°C).............320mW5-Pin SOT23 (derate 7.1mW/°C above
70°C)............571mWOperating Temperature Range.........................-40°C
to
125°CStorage
Temperature
Range.............................-65°C
to
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150°CJunction Temperature......................................................
150°CLead
http://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.htmlTemperature
(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
2_______________________________________________________________________________
________
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
(VCC= 5V, CSRT= 1500pF, TA =
25°C, unless otherwise noted.)
SUPPLY CURRENTRESET TIMEOUT PERIODvs. SUPPLY VOLTAGE
RESET TIMEOUT PERIOD vs. CSRT
vs. TEMPERATURE
4.010,0002
4.30
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0cot http://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.html63.52/1246)
)
Xs
1000
sA)
mMmA3.0(( 4.25
? DD( OTINOIRRE2.5EERP100
P
R2.0TTUUUCO4.20
YOEEL1.5MMPIIPT10
T
UTTSEE1.0SSEERR4.15
1
0.500.14.10
1
2
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3
4
56
0.001
0.01
0.1
110
100
1000
-50
-25
25
50
75
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100
125
SUPPLY VOLTAGE (V)
CSRT (nF)
TEMPERATURE (°C)
RESET TIMEOUT PERIOD
MAXIMUM TRANSIENT DURATIONVvs. TEMPERATURE
CC TO RESET DELAY
vs. RESET THRESHOLD OVERDRIVE
vs. TEMPERATURE (VCC FALLING)
600175160
550150
150)s)
?s?)(500s (D N125?140(OO IYRITAE450100L130PAE RTD UTO400UD EET75S120MNERI T
350EISOTNT
110EA50 SCECR300RTV10025025
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http://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.html90
200
80-50
-25
25
50
75
100125
200
400
600
800
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1000
-50
-25
255075100
125
TEMPERATURE (°C)RESET THRESHOLD OVERDRIVE (mV)
TEMPERATURE (°C)
POWER-UP/POWER-DOWN
NORMALIZED RESET THRESHOLD
CHARACTERISTIC
vs. TEMPERATURE
8
1.0060cot 62/1D
24L1.0046OXAHMSER1V/div
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H1.002T TESER1.000 DEZILA0.998MRON1V/div
0.9960.994
400?s/div
-50-250255075100125
TEMPERATURE (°C)
________________________________________________________________________________
_______3
MAX6340/MAX6421–MAX6426
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
MAX6340/MAX6421–MAX6426
Dhttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.htmletailed Description
Reset Output
The reset output is typically connected to the reset inputof a ?P. A ?P’s reset input
starts or restarts the ?P in aknown state. The MAX6340/MAX6421–MAX6426 ?Psupervisory
circuits provide the reset logic to preventcode-execution errors during power-up,
power-down,and brownout conditions (see Typical OperatingCharacteristics).
RESETchanges from high to low whenever VCCdropsbelow the threshold voltage. Once
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VCCexceeds thethreshold voltage, RESETremains low for the capacitor-adjustable reset
timeout period.
The MAX6422 active-high RESET output is the inverselogic of the active-low
RESEToutput. All device outputsare guaranteed valid for VCC> 1V.
The MAX6340/MAX6423/MAX6425/MAX6426 are open-drain RESEToutputs. Connect an
external pullup resis-tor to any supply from 0 to 5.5V. Select a resistor valuelarge
enough
to
register
a
logic
low
RESETisassertedhttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.html
when
and
small enough to register a logic highwhile supplying all input current and leakage
pathsconnected to the RESETline. A 10k?to 100k?pullupis sufficient in most
applications.
Figure 1. MAX6340/MAX6423/MAX6425/MAX6426 Open-DrainRESETOutput Allows Use with
Multiple Supplies
Selecting a Reset Capacitor
The reset timeout period is adjustable to accommodatea variety of ?P applications.
Adjust the reset timeoutperiod (tRP) by connecting a capacitor (CSRT) betweenSRT and
ground. Calculate the reset timeout capacitoras follows:
4_______________________________________________________________________________
________
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
CSRT= (tRP- 275?s) / (2.73 ?106)
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where tRPis in seconds and CSRTis in farads.
The reset delay time is set by a current/capacitor-con-trolled ramp compared to an
internahttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.htmll
0.65V
reference.An internal 240nA ramp current source charges theexternal capacitor. The
charge to the capacitor iscleared when a reset condition is detected. Once thereset
condition is removed, the voltage on the capacitorramps according to the formula:
dV/dt = I/C. The CSRTcapacitor must ramp to 0.65V to deassert the reset.CSRTmust be
a low-leakage (
Interfacing to Other Voltages for Logic
Compatibility
The open-drain outputs of the MAX6340/MAX6423/MAX6425/MAX6426 can be used to
interface to ?Ps withother logic levels. As shown in Figure 1, the open-drainoutput
can be connected to voltages from 0 to 5.5V. Thisallows for easy logic compatibility
to various ?Ps.
MAX6340/MAX6421–MAX6426
Wired-OR Reset
To allow auxiliary circuitry to hold the system in reset,an external open-drain logic
signal can be connectedto the open-drain RESETof the MAX6340/MAX6423/MAX6425/MAX6426,
ashttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.html shown in Figure 2.
This config-uration can reset the ?P, but does not provide the resettimeout when the
external logic signal is released.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 graph Maximum
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TransientDuration
vs.
Reset
Threshold
Overdrive
in
the
TypicalOperating
Characteristicsshows this relationship.
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 actualOperating as a Voltage Detector
The MAX6340/MAX6421–MAX6426 can be operated in avoltage detector mode by floating
the SRT pin. The resetdelay times for VCCrising above or falling below thethreshold
are
not
significantly
different.
The
reset
output
isdeassehttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.htmlrted
smoothly without false pulses.
Negative-Going VCCTransients
reset
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 doesnot
cause a reset pulse to be issued.
Ensuring a Valid RESET or RESET
Down to VCC= 0
When Ving (sourcing) capabilities decline drastically. In theCCfalls below 1V,
RESET/RESET current-sink-case of the MAX6421/MAX6424, high-impedanceCMOS-logic
inputs connected to RESETcan drift toundetermined voltages. This presents no problems
inmost applications, since most ?Ps and other circuitrydo not operate with VCCbelow
1V.
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In those applications where RESETmust be valid downto zero, adding a pulldown
resistorhttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.html
between
RESETand ground sinks any stray leakage currents, holdingRESETlow (Figure 3). 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 MAX6422,
a 100k?pullup resis-
________________________________________________________________________________
_______
5
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
MAX6340/MAX6421–MAX6426
Figure 3. Ensuring RESETValid to VCC
= 0
CC
tor between RESET and VCCholds RESET high whenVCCfalls below 1V (Figure 4). Open-drain
RESETver-sions are not recommended for applications requiringvalid logic for VCCdown
to zero.
Layout Consideration
SRT is a precise current source. When developing thelayout for the application, be
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careful
to
minimize
boardcapacitance
and
leakage
chttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.htmlurrents around this
pin.Traces connected to SRT should be kept as short aspossible. Traces carrying
high-speed digital signalsand traces with large voltage potentials 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.
6
________________________________________________________________________________
_______
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
factory for availability of nonstandard versions.
7
MAX6340/MAX6421–MAX6426
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
MAX6340/MAX6421–MAX6426
Chip Information
TRANSISTOR COUNT: 295PROCESS: BiCMOS
8__________http://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.html_________
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____________________________________________________________________
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
Package Information
(The package drawing(s) in this data sheet may not reflect the most current
specifications.
For
the
latest
package
outline
information,go
to
www.maxim-ic.com/packages.)
________________________________________________________________________________
_______9
MAX6340/MAX6421–MAX6426
Low-Power, SC70/SOT ?P Reset Circuits withCapacitor-Adjustable Reset Timeout Delay
MAX6340/MAX6421–MAX6426
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current
specifications.
For
the
latest
package
outline
information,go
to
www.maxim-ic.com/packages.)
Maxim
cannot
assume
responsibility
for
use
of
any
circuitry
circuitrhttp://www.wenkuxiazai.com/doc/4b32722a5901020207409cff.htmly
other
than
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.
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10____________________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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