can be adjusted to any voltage above 1.22V, usingoAdjustable Watchdog Timeoutexternal resistors. In addition, the reset and watchdogtimeout periods are adjustable using external capaci-o500x Watchdog Timeout Multipliertors. A watchdog select pin extends the watchdog time-o4µA Supply Current
out period to 500x. The reset function features immunityoRESET or RESETOutput Options
to power-supply transients.
oPush-Pull or Open-Drain Output OptionsThese four devices differ only in the structure of their reseto
Guaranteed RESETAsserted At or Aboveoutputs (see the Selector Guide). The MAX6301–MAX6304VCC= 1V (MAX6301/MAX6303)are available in the space-saving 8-pin µMAX®package,as well as 8-pin PDIP and SO packages.
oPower-Supply Transient ImmunityApplicationsoWatchdog Function can be DisabledoPDIP/SO/µMAX Packages AvailableMedical EquipmentEmbedded ControllersIntelligent InstrumentsCritical µP MonitoringOrdering InformationPortable EquipmentSet-Top BoxesBattery-Powered ComputersPARTTEMP RANGEPIN-PKGComputers/Controllers
PACKAGECODESelector GuideMAX6301CPA0°C to +70°C8 PDIPP8-1MAX6301CSA0°C to +70°C8 SOS8-2FEATUREMAX6301MAX6302MAX6303MAX6304MAX6301CUA0°C to +70°C8 µMAXU8-1Acti ve-Low √—√—MAX6301EPA-40°C to +85°C8 PDIPP8-1ResetMAX6301ESA-40°C to +85°C8 SOS8-2Acti ve-H ig h Reset—√—√Devices are available in both leaded and lead-free packaging.Specify lead-free by adding the “+” symbol at the end of thepart number when ordering.Op en- Dr ai nReset Outp ut√√——Ordering Information continued at end of data sheet.P ush- Pu l l Reset Outp ut——√√Typical Operating CircuitP in - Pa ckag e8- PD IP /S O/8- PD IP /S O/8- PD IP /S O/8- PD IP /S O/VINµM AX µM AX µM AX µM AX MAX6301ONLYPin ConfigurationR1TOP VIEW1RESET INVCC8RL0.1µFRESET IN18VCCR2GND27RESET (RESET)2MAX6301GNDRESET7(RESET)RESETSRT3MAX6302MAX63036WDIMAX6301RLMAX6302µPSWT4MAX63045WDS3MAX6302ONLYSRTMAX6303WDI6I/O4DIP/SO/µMAXSWTMAX6304WDS5( ) ARE FOR MAX6302/MAX6304.CSRTCSWT*Patents pendingWDS = 0 FOR NORMAL MODE( ) ARE FOR MAX6302/MAX6304.WDS = 1 FOR EXTENDED MODEµMAX is a registered trademark of Maxim Integrated Products, Inc.________________________________________________________________Maxim Integrated Products1
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.MAX6301–MAX6304元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogMAX6301–MAX6304ABSOLUTE MAXIMUM RATINGS
VCC....................................................................................-0.3V to +7.0VRESET IN, SWT, SRT..................................-0.3V to (VCC+ 0.3V)WDI, WDS..............................................................-0.3V to +7.0VRESET, RESET
MAX6301….......................................................-0.3V to +7.0VMAX6302/MAX6303/MAX6304...............-0.3V to (VCC+ 0.3V)Input Current
VCC...............................................................................±20mAGND..............................................................................±20mAOutput Current
RESET, RESET..............................................................±20mA
Continuous Power Dissipation (TA= +70°C)
PDIP (derate 9.09mW/°C above +70°C)......................727mWSO (derate 5.88mW/°C above +70°C).........................471mWµMAX (derate 4.10mW/°C above +70°C)....................330mWOperating Temperature Range
MAX630_C_A......................................................0°C to +70°CMAX630_E_A...................................................-40°C to +85°CStorage Temperature Range.............................-65°C to +160°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= +2V to +5.5V, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.)PARAMETEROperating Voltage Range(Note 1)Supply Current (Note 2)RESET TIMERReset Input Threshold VoltageReset Input HysteresisReset Input Leakage CurrentReset Output-Voltage High(MAX6302/MAX6303/MAX6304)VTHVHYSTIRESET INVCC ≥ 4.5V, ISOURCE = 0.8mAVOHVCC = 2V, ISOURCE = 0.4mAMAX6302/MAX6304, VCC = 1.31V,RL = 10kΩVCC ≥ 4.5V, ISINK = 3.2mAVCC = 2V, ISINK = 1.6mAReset Output-Voltage Low(MAX6301/MAX6303/MAX6304VOLMAX6301/MAX6303tRDtRItRPVCC = 1V, ISINK = 50µA,TA = 0°C to +70°CVCC = 1.2V, ISINK = 100µA,TA = -40°C to +85°C63262.84.05.2±1±1VCC -0.30.40.40.30.3µsµsmsµAVVCC - 0.4VCC - 0.4VVRESET IN falling, VCC = 5.0VVRESET IN rising, VCC = 5.0V1.1951.2201.24020±0.01±11.2451.265VmVnASYMBOLVCCICCCONDITIONSMAX6301C/MAX6303CMAX6301E/MAX6303EMAX6302/MAX6304No loadMIN1.001.201.314.0TYPMAX5.505.505.507.0µAVUNITSVCC to Reset DelayReset Input Pulse WidthReset Timeout Period (Note 3)Reset Output Leakage CurrentVCC = falling at 1mV/µsComparator overdrive = 50mVCSRT = 1500pFMAX6301, VRESET = VCCMAX6302, VRESET = GND2_______________________________________________________________________________________
元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogELECTRICAL CHARACTERISTICS (continued)
(VCC= +2V to +5.5V, TA= TMINto TMAX, unless otherwise noted. Typical values are at VCC= +5V and TA= +25°C.)PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSWATCHDOG TIMERWDI, WDS Input ThresholdVIH0.7 x VCCVIL0.3 x VVCCWDI Pulse WidthtV30WPCC = 4.5V to 5.5VVCC = 2V to 4.5V60nsWDI, WDS Leakage CurrentExtended mode disabled±1µAWDI Sink/Source Current (Note 4)Extended mode enabled±70µAWatchdog Timeout PeriodWDS = GND, CSWT = 1500pF2.84.05.2ms(Note 3)tWDWDS = VCC, CSWT = 1500pF1.42.02.6sNote 1:Reset is guaranteed valid from the selected reset threshold voltage down to the minimum VCC.Note 2:WDS = VCC, WDI unconnected.
Note 3:Precision timing currents of 500nA are present at both the SRT and SWT pins. Timing capacitors connected to these nodes
must have low leakage consistent with these currents to prevent timing errors.
Note 4:The sink/source is supplied through a resistor, and is proportional to VCC(Figure8). At VCC= 2V, it is typically ±24µA.
__________________________________________Typical Operating Characteristics(CSWT= CSRT= 1500pF, TA= +25°C, unless otherwise noted.)
RESET TIMEOUT PERIOD
EXTENDED-MODE
NORMAL-MODE
vs. CWATCHDOG TIMEOUT PERIOD vs. CSRT
SWT
WATCHDOG TIMEOUT PERIOD vs. CSWT
10,000
(WDS = VCC)
(WDS = GND)
1V0CC = 5Vco10,00023tV00 4CC = 5V10,000cc-oo1tt 04V43-CC = 5V-611X00A33M6X)6X))AsAssMMm1000(m (D1000( 1000 DODIOROIIREREPE P100
TP TU100
T100
UOUOEOEMEMITMII T10
GT TO10G10
EDOSHDERCH1
TCA1TWAW1
00.001
0.01
0.1
110
100
1000
00.1
C10
100
1000
0.001
0.01
0.1
110
100
1000
SRT (nF)
0.001
0.01
0.1
1CSWT (nF)
CSWT (nF)
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MAX6301–MAX6304元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogMAX6301–MAX6304____________________________Typical Operating Characteristics (continued)(CSWT= CSRT= 1500pF, TA= +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6301-4 toc04RESET AND NORMAL-MODEWATCHDOG TIMEOUT PERIOD
vs. TEMPERATURE
MAX6301-4 toc05MAXIMUM TRANSIENT DURATION vs. RESET THRESHOLD OVERDRIVE (VRST)
120110100TRANSIENT DURATION (µs)9080706050403020100
VRST = 4.60V0
200
400
600
800
1000
RESET OCCURS ABOVE THE CURVESEE THE NEGATIVE-GOING VCC TRANSIENTS SECTIONMAX6301-4 toc064.24.0SUPPLY CURRENT (µA)3.8
RESET DEASSERTED NO LOAD4.204.154.10tRP/tWD (ms)4.054.003.953.903.853.80
VCC = 5.0V3.63.43.23.02.82.6
1.5
2.02.53.03.54.0
4.55.05.56.0
SUPPLY VOLTAGE (V)
-60-40-20020406080100
TEMPERATURE (°C)RESET THRESHOLD OVERDRIVE (mV)
SUPPLY CURRENT vs. TEMPERATURE
MAX6301-4 toc07RESET IN THRESHOLD VOLTAGE
vs. TEMPERATURE
MAX6301-4 toc085.004.754.50SUPPLY CURRENT (µA)4.254.003.753.503.253.002.752.50
-60
-40
-20
0
20
40
60
80
VCC = 2.0VVCC = 5.0V RESET DEASSERTED NO LOAD1.226RESET REFERENCE VOLTAGE (V)1.2241.2221.2201.2181.2161.214
-60
100-40-20020406080100
TEMPERATURE (°C)TEMPERATURE (°C)
VCC TO RESET DELAY
vs. TEMPERATURE (VCC FALLING)
VCC FALLING AT 1mV/µs72PROPAGATION DELAY (µs)6864605652-60
4.00
MAX6301-4 toc09RESET AND WATCHDOG TIMEOUT vs. SUPPLY VOLTAGE
MAX6301-4 toc10764.16
4.12tRP/tWP (ms)4.08
4.04
3.96
-40-20
0
20
40
60
80
100
2
3
4VCC (V)
5
6
TEMPERATURE (°C)
4_______________________________________________________________________________________
元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogPin DescriptionPINNAMEFUNCTIONReset Input. High-impedance input to the reset comparator. Connect this pin to the center point of an1RESET INexternal resistor voltage-divider network to set the reset threshold voltage. The reset threshold voltage iscalculated as follows: VRST = 1.22 x (R1 + R2) / R2 (see the Typical Operating Circuit).2GNDGroundSet Reset-Timeout Input. Connect a capacitor between this input and ground to select the reset timeout3SRTperiod (tRS). Determine the period as follows: tRP = 2.67 x CSRT, with CSRT in pF and tRP in µs (see theTypical Operating Circuit).Set Watchdog-Timeout Input. Connect a capacitor between this input and ground to select the basic4SWTwatchdog timeout period (tWD). Determine the period as follows: tWD = 2.67 x CSWT, with CSWT in pF andtWD in µs. The watchdog function can be disabled by connecting this pin to ground.Watchdog-Select Input. This input selects the watchdog mode. Connect to ground to select normal mode5WDSand the basic watchdog timeout period. Connect to VCC to select extended mode, multiplying the basictimeout period by a factor of 500. A change in the state of this pin resets the watchdog timer to zero.Watchdog Input. A rising or falling transition must occur on this input within the selected watchdog timeoutperiod, or a reset pulse will occur. The capacitor value selected for SWT and the state of WDS determine6WDIthe watchdog timeout period. The watchdog timer clears and restarts when a transition occurs on WDI orWDS. The watchdog timer is cleared when reset is asserted and restarted after reset deasserts. In theextended watchdog mode (WDS = VCC), the watchdog function can be disabled by driving WDI with athree-stated driver or by leaving WDI unconnected.RESETOpen-Drain, Active-Low ResetRESET changes from high to low whenever the monitored voltage (VIN)Output (MAX6301)drops below the selected reset threshold (VRST). RESET remains low as(MAX6301/long as VIN is below VRST. Once VIN exceeds VRST, RESET remains lowMAX6303)for the reset timeout period and then goes high. The watchdog timerPush-Pull, Active-Low Resettriggers a reset pulse (tOutput (MAX6303)RP) whenever the watchdog timeout period (tWD)7is exceeded.RESETOpen-Drain, Active-High ResetRESET changes from low to high whenever the monitored voltage (VIN)(MAX6302/Output (MAX6302)drops below the selected reset threshold (VRST). RESET remains high aslong as VIN is below VRST. Once VIN exceeds VRST, RESET remains highMAX6304for the reset timeout period and then goes low. The watchdog timerPush-Pull, Active-High Resettriggers a reset pulse (tOutput (MAX6304)RP) whenever the watchdog timeout period (tWD)is exceeded.8VCCSupply Voltage_______________________________________________________________________________________5
MAX6301–MAX6304元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogMAX6301–MAX6304Detailed DescriptionReset Function/OutputThe reset output is typically connected to the reset inputof a µP. A µP’s reset input starts or restarts the µP in aknown state. The MAX6301–MAX6304 µP supervisorycircuits provide the reset logic to prevent code-executionerrors during power-up, power-down, and brownoutconditions (see the Typical Operating Circuit).
For the MAX6301/MAX6303, RESETchanges from highto low whenever the monitored voltage (VIN) dropsbelow the reset threshold voltage (VRST). RESETremains low as long as VINis below VRST. Once VINexceeds VRST, RESETremains low for the reset timeoutperiod, then goes high. When a reset is asserted due toa watchdog timeout condition, RESETstays low for thereset timeout period. Any time reset asserts, the watch-dog timer clears. At the end of the reset timeout period,RESETgoes high and the watchdog timer is restartedfrom zero. If the watchdog timeout period is exceededagain, then RESETgoes low again. This cycle contin-ues unless WDI receives a transition.
On power-up, once VCCreaches 1V, RESETis guaran-teed to be a logic-low. For information about applica-tions where VCCis less than 1V, see the Ensuring aValid RESET/RESET Output Down to VCC= 0V (MAX6303/MAX6304) section. As VCCrises, RESETremains low.When VINrises above VRST, the reset timer starts andRESETremains low. When the reset timeout periodends, RESETgoes high.
On power-down, once VINgoes below VRST, RESETgoes low and is guaranteed to be low until VCCdropsbelow 1V. For information about applications whereVCCis less than 1V, see the Ensuring a ValidRESET/RESET Output Down to VCC= 0V (MAX6303/MAX6304)section.
The MAX6302/MAX6304 active-high RESET output isthe inverse of the MAX6301/MAX6303 active-lowRESEToutput, and is guaranteed valid for VCC> 1.31V.
R1RESET INR2VCC0.1µFVINMAX6301MAX6302MAX6303MAX6304VRST = 1.22 R1 + R2R2()Figure 1. Calculating the Reset Threshold Voltage (VRST)and R2 can have very high values to minimize currentconsumption. Set R2 to some conveniently high value(1MΩ, for example) and calculate R1 based on the desiredreset threshold voltage, using the following formula:
⎛VRST⎞R1=R2×⎜−1⎟ Ω⎝VTH⎠()Watchdog TimerThe watchdog circuit monitors the µP’s activity. If the µP
does not toggle the watchdog input (WDI) within tWD(user selected), reset asserts. The internal watchdogtimer is cleared by reset, by a transition at WDI (whichcan detect pulses as short as 30ns), or by a transitionat WDS. The watchdog timer remains cleared whilereset is asserted; as soon as reset is released, the timerstarts counting (Figure2).
The MAX6301–MAX6304 feature two modes of watchdogtimer operation: normal mode and extended mode. Innormal mode (WDS = GND), the watchdog timeoutperiod is determined by the value of the capacitor con-nected between SWT and ground (see the Selectingthe Reset and Watchdog Timeout Capacitorsection). Inextended mode (WDS = VCC), the watchdog timeoutperiod is multiplied by 500. For example, in the extendedmode, a 1µF capacitor gives a watchdog timeout periodof 22 minutes (see the Extended-Mode WatchdogTimeout Period vs. CSWTgraph in the TypicalOperating Characteristics).
In extended mode, the watchdog function can bedisabled by leaving WDI unconnected or by three-statingthe driver connected to WDI. In this mode, the watchdoginput is internally driven low during the watchdog timeoutperiod, then momentarily pulses high, resetting the
Reset ThresholdThese supervisors monitor the voltage on RESET IN.The MAX6301–MAX6304 have an adjustable resetthreshold voltage (VRST) set with an external resistorvoltage-divider (Figure1). Use the following formula tocalculate VRST(the point at which the monitored voltagetriggers a reset):VRST=VTH×R1+R2R2() V()where VRSTis the desired reset threshold voltage andVTHis the reset input threshold (1.22V). Resistors R1
6
_______________________________________________________________________________________
元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogVCCWDItWDtRP0VVCCRESET0VNORMAL MODE (WDS = GND)Figure 2a. Watchdog Timing Diagram, WDS = GNDVCCWDItWD x 500tRP0VVCCRESET0VEXTENDED MODE (WDS = VCC)Figure 2b. Watchdog Timing Diagram, WDS = VCCwatchdog counter. When WDI is left unconnected, thewatchdog timer is cleared by this internal driver justbefore the timeout period is reached (the internal driverVpulls WDI high at about 94% of tCCthree-stated, the maximum allowable leakage current ofWD). When WDI isthe device driving WDI is 10µA.
GNDVCCIn normal mode (WDS = GND), the watchdog timerSRTMAX63010.1µFcannot be disabled by three-stating WDI. WDI is aMAX6302high-impedance input in this mode. Do not leave WDIunconnected in normal mode.
SWTMAX6303MAX6304Applications InformationCSRTCSWTSelecting the Reset and WatchdogTimeout CapacitorThe reset timeout period is adjustable to accommodateCRST = tRPa variety of µP applications. Adjust the reset timeout2.67CSWT = tWD2.67CRST in pFCSWT in pFperiod (ttWD in µstWD in µs(CRS) by connecting a specific value capacitorSRT) between SRT and ground (Figure3). Calculatethe reset timeout capacitor as follows:
CSRT= tRP/ 2.67
Figure 3. Calculating the Reset (CSRT) and Watchdog (CSWT)Timeout Capacitor Values_______________________________________________________________________________________
7
MAX6301–MAX6304元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogMAX6301–MAX6304VINVCCVCC80C51VCCRSTVCCVCCR1RESET INR2VCC0.1µFMAX6302RESETMAX6301MAX6302MAX6303MAX6304WDIWDSGND*I/OI/OI/OGNDVRST = 1.22 (R1 + R2R2)*THREE-STATE LEAKAGE MUST BE < 10µA.Figure4. Monitoring Votlages Other than VCCFigure 5. Wake-Up Timerwith CSRTin pF and tRPin µs. CSRTmust be a low-leak-age (< 10nA) type capacitor. Ceramic is recommended.
The watchdog timeout period is adjustable to accom-modate a variety of µP applications. With this feature,the watchdog timeout can be optimized for softwareexecution. The programmer can determine how oftenthe watchdog timer should be serviced. Adjust thewatchdog timeout period (tWD) by connecting a specif-ic value capacitor (CSWT) between SWT and ground(Figure3). For normal-mode operation, calculate thewatchdog timeout capacitor as follows:
CSWT= tWD/ 2.67
where CSWTis in pF and tWDis in µs. CSWTmust be alow-leakage (< 10nA) type capacitor. Ceramic isrecommended.
The Typical Operating Circuitmonitors VCC. Voltagesother than VCCcan easily be monitored, as shown inFigure4. Calculate VRSTas shown in the ResetThreshold section.
watchdog timeout period ends, a reset is applied onthe 80C51, waking it up to perform tasks. While the µPis performing tasks, the 80C51 pulls WDS low (select-ing normal mode), and the MAX6302 monitors the µPfor hang-ups. When the µP finishes its tasks, it putsitself back into sleep mode, drives WDS high, andstarts the cycle over again. This is a power-saving tech-nique, since the µP is operating only part of the timeand the MAX6302 has very low quiescent current.
Adding a Manual Reset FunctionA manual reset option can easily be implemented by con-necting a normally open momentary switch in parallelwithR2 (Figure6). When the switch is closed, the voltage onRESET IN goes to zero, initiating a reset. When theswitch is released, the reset remains asserted for thereset timeout period and then is cleared. The pushbut-ton switch is effectively debounced by the reset timer.
VCCMonitoring Voltages Other than VCCWake-Up TimerIn some applications, it is advantageous to put a µPinto sleep mode, periodically wake it up to performchecks and/or tasks, then put it back into sleep mode.The MAX6301 family of supervisors can easily accom-modate this technique. Figure5 illustrates an exampleusing the MAX6302 and an 80C51.
In Figure5, just before the µC puts itself into sleepmode, it pulls WDS high. The µC’s I/O pins maintaintheir logic levels while in sleep mode and WDS remainshigh. This places the MAX6302 in extended mode,increasing the watchdog timeout 500 times. When the
8
R1RESET INVCC0.1µFR2MAX6301MAX6302MAX6303MAX6304Figure 6. Adding a Manual Reset Function_______________________________________________________________________________________
元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogRESET TO OTHER SYSTEM COMPONENTSVCCVCCTO RESETGENERATORµPWDIMAX6301WATCHDOGTIMERVCC0.1µFGND4.7kΩMAX6301MAX6302WDSTO MODEMAX6303RESETRESETCONTROLMAX6304Figure 7. Interfacing to µPs with Bidirectional Reset I/O PinsFigure 8. Watchdog Input StructureInterfacing to µPs withWatchdog Input CurrentBidirectional Reset PinsSince RESETis open-drain, the MAX6301 interfacesExtended Modeeasily with µPs that have bidirectional reset pins, suchIn extended mode (WDS = VCC), the WDI input is inter-as the Motorola 69HC11 (Figure7). Connecting RESETnally driven through a buffer and series resistor fromdirectly to the µP’s reset pin with a single pullup allowsthe watchdog counter (Figure8). When WDI is lefteither device to assert reset.
unconnected, the watchdog timer is serviced within thewatchdog timeout period by a very brief low-high-lowNegative-Going VIn addition to issuing a reset to the µP during power-up,CCTransientspulse from the counter chain. For minimum watchdoginput current (minimum overall power consumption),power-down, and brownout conditions, these supervisorsleave WDI low for the majority of the watchdog timeoutare relatively immune to short-duration negative-goingperiod, pulsing it low-high-low (> 30ns) once within thetransients (glitches). The Maximum Transient Duration vs.period to reset the watchdog timer. If instead WDI isReset Threshold Overdrive graph in the Typicalexternally driven high for the majority of the timeoutOperating Characteristicsshows this relationship.
period, typically 70µA can flow into WDI.
The area below the curves of the graph is the region inNormal Modewhich these devices typically do not generate a resetIn normal mode (WDS = GND), the internal buffer thatpulse. This graph was generated using a negative-drives WDI is disabled. In this mode, WDI is a standardgoing pulse applied to VIN, starting above the actualCMOS input and leakage current is typically 100pA,reset threshold (Vregardless of whether WDI is high or low.
nitude indicated (reset-threshold overdrive). As theRST) and ending below it by the mag-magnitude of the transient increases (farther below theEnsuring a Valid RESET/RESET Outputreset threshold), the maximum allowable pulse widthDown to Vdecreases. Typically, a VWhen VCC= 0V (MAX6303/MAX6304)CCfalls below 1V, RESET/RESET current sinkingbelow the reset threshold and lasts 50µs or less will notCCtransient that goes 100mV(sourcing) capabilities decline drastically. In the casecause a reset pulse to be issued.
of the MAX6303, high-impedance CMOS-logic inputsconnected to RESETcan drift to undeterminedvoltages. This presents no problem in most applica-tions, since most µPs and other circuitry do not operatewith VCCbelow 1V.
_______________________________________________________________________________________9
MAX6301–MAX6304元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogMAX6301–MAX6304VCCVCC100kΩVCC0.1µFMAX6303VCC0.1µFMAX6304RESET100kΩGNDRESETGNDFigure 9. Ensuring RESETValid to VCC= 0VFigure 10. Ensuring RESET Valid to VCC= 0VIn those applications where RESETmust be valid downto 0V, adding a pulldown resistor between RESETandground sinks any stray leakage currents, holdingRESETlow (Figure9). The value of the pulldown resistoris not critical; 100kΩis large enough not to load RESETand small enough to pull RESETto ground. For applica-tions using the MAX6304, a 100kΩpullup resistorbetween RESET and VCCwill hold RESET high whenVCCfalls below 1V (Figure10).
STARTSET WDILOWWatchdog-Software ConsiderationsTo help the watchdog timer monitor software executionmore closely, set and reset the watchdog input at differ-ent points in the program, rather than pulsing thewatchdog input high-low-high or low-high-low. Thistechnique avoids a stuck loop in which the watchdogtimer would continue to be reset within the loop, keepingthe watchdog from timing out.
Figure11 shows an example of a flow diagram wherethe I/O driving the watchdog input is set high at thebeginning of the program, set low at the beginning ofevery subroutine or loop, then set high again when theprogram returns to the beginning. If the program shouldhang in any subroutine the problem would quickly becorrected, since the I/O is continually set low and thewatchdog timer is allowed to time out, causing a resetor interrupt to be issued. When using extended mode,as described in the Watchdog Input Current section,this scheme does result in higher average WDI inputcurrent than does the method of leaving WDI low for themajority of the timeout period and periodically pulsing itlow-high-low.
SUBROUTINE ORPROGRAM LOOPSET WDI HIGHRETURNENDFigure 11. Watchdog Flow DiagramLayout ConsiderationsSRT and SWT are precision current sources. Whendeveloping the layout for the application, be careful tominimize board capacitance and leakage currentsaround these pins. Traces connected to these pins
10
should be kept as short as possible. Traces carryinghigh-speed digital signals and traces with large voltagepotentials should be routed as far from these pins aspossible. Leakage currents and stray capacitance(e.g., a scope probe) at these pins could cause errorsin the reset and/or watchdog timeout period. Whenevaluating these parts, use clean prototype boards toensure accurate reset and watchdog timeout periods.RESET IN is a high-impedance input that is typicallydriven by a high-impedance resistor-divider network(e.g., 1MΩto 10MΩ). Minimize coupling 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. Notethat sensitive pins are located on the GND side of thedevice, away from the digital I/O, to simplify board layout.
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元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogOrdering Information (continued)Chip InformationPARTTEMP RANGEPIN-PKGTRANSISTOR COUNT: 580
PACKAGECODEMAX6302CPA0°C to +70°C8 PDIPP8-1MAX6302CSA0°C to +70°C8 SOS8-2MAX6302CUA0°C to +70°C8 µMAXU8-1MAX6302EPA-40°C to +85°C8 PDIPP8-1MAX6302ESA-40°C to +85°C8 SOS8-2MAX6303CPA0°C to +70°C8 PDIPP8-1MAX6303CSA0°C to +70°C8 SOS8-2MAX6303CUA0°C to +70°C8 µMAXP8-1MAX6303EPA-40°C to +85°C8 PDIPS8-2MAX6303ESA-40°C to +85°C8 SOU8-1MAX6304CPA0°C to +70°C8 PDIPP8-1MAX6304CSA0°C to +70°C8 SOS8-2MAX6304CUA0°C to +70°C8 µMAXP8-1MAX6304EPA-40°C to +85°C8 PDIPS8-2MAX6304ESA-40°C to +85°C8 SOU8-1Devices are available in both leaded and lead-free packaging.Specify lead-free by adding the “+” symbol at the end of thepart number when ordering.______________________________________________________________________________________11
MAX6301–MAX6304元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogMAX6301–MAX6304Package Information(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline informationgo to www.maxim-ic.com/packages.)
8LUMAXD.EPS84X S8INCHESDIMAA1A2bcDeEHMIN-0.0020.030MAX0.0430.0060.037MILLIMETERSMAXMIN-0.050.751.100.150.95Ø0.50±0.10.6±0.1EH10.6±0.11DLαSBOTTOM VIEW0.0140.0100.0070.0050.1200.1160.0256 BSC0.1200.1160.1980.1880.0260.0166°0°0.0207 BSC0.250.360.130.182.953.050.65 BSC2.953.054.785.030.410.660°6°0.5250 BSCTOP VIEWA2A1AcebLαSIDE VIEWFRONT VIEWPROPRIETARY INFORMATIONTITLE:PACKAGE OUTLINE, 8L uMAX/uSOPAPPROVALDOCUMENT CONTROL NO.REV.21-0036J1112______________________________________________________________________________________
元器件交易网www.cecb2b.com+5V, Low-Power µP Supervisory Circuits with Adjustable Reset/WatchdogPackage Information (continued)(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline informationgo to www.maxim-ic.com/packages.)
SPE. INCHESMILLIMETERSNCIDIMMINMAXMINMAXOSA0.0530.0691.351.75NA10.0040.0100.100.25B0.0140.0190.350.49C0.0070.0100.190.25e0.050 BSC1.27 BSCE0.1500.1573.804.00EHH0.2280.2445.806.20L0.0160.0500.401.27VARIATIONS:1INCHESMILLIMETERSTOP VIEWDIMMINMAXMINMAXNMS012D0.1890.1974.805.008AAD0.3370.3448.558.7514ABD0.3860.3949.8010.0016ACDACeBA10∞-8∞LFRONT VIEWSIDE VIEWPROPRIETARY INFORMATIONTITLE:PACKAGE OUTLINE, .150\" SOICAPPROVALDOCUMENT CONTROL NO.REV.21-0041B11Revision HistoryPages changed at Rev 2: 1, 13
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.Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________13©2007 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
MAX6301–MAX6304
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