19-2531; Rev 1; 4/03
Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
General Description
FeaturesThe MAX6736–MAX6745 are low-power dual-/triple-voltage microprocessor (µP) supervisors. TheseoDual-/Triple-Supply Reset Voltage Monitorsdevices assert a reset if any monitored supply fallsoPrecision Factory-Set Reset Thresholds forbelow its factory-trimmed or adjustable threshold andMonitoring from 0.9V to 5.0V
maintain reset for a minimum timeout period after alloAdjustable Reset Input Down to 0.488V
supplies rise above their thresholds. The integratedo150ms and 1200ms (min) Reset Timeout Perioddual/triple supervisory circuits significantly reduce sizeOptions
and power compared to separate ICs or discrete com-ponents. The low supply current of 6µA makes theseoVCC1 Power-OK Output for Power-Supply
devices ideal for portable equipment.
Sequencing Applications (MAX6741/MAX6744)The MAX6736/MAX6737 are dual fixed-voltage µPoPower-Fail Input/Power-Fail Outputsupervisors with a manual reset input. The MAX6738/(MAX6742/MAX6745)MAX6739 have one fixed and one adjustable reseto6µA Supply Currentthreshold and a manual reset input. The MAX6740/oTiny SC70 Package
MAX6743 are triple-voltage µP supervisors with twofixed and one user-adjustable reset threshold inputs.Ordering InformationThe MAX6741/MAX6744 are dual-voltage µP supervi-sors with a power-OK (POK) output ideal for power-PARTTEMP RANGEPIN-PACKAGEsupply sequencing. The MAX6742/MAX6745 monitorMAX6736XK_ _D_-T-40°C to +85°C5 SC70-5the primary Vpower-fail comparator.
CCsupply and have an independentMAX6737XK_ _D_-T-40°C to +85°C5 SC70-5The MAX6736–MAX6745 monitor I/O supply voltagesNote:The first “_ _” or “_” are placeholders for the thresholdvoltage levels of the devices. Desired threshold levels are set(Vby the part number suffix found in Tables 1 and 2. The “_” after(VCC1) from 1.8V to 5.0V and core supply voltagesCC2) from 0.9V to 3.3V with factory-trimmed resetthe D is a placeholder for the reset timeout period suffix foundthreshold voltage options (Table 1). An externalin Table 3. For example, the MAX6736XKLTD3-T is a dual-volt-adjustable RSTIN input option allows monitoring volt-age supervisor VTH1 = 4.625V, VTH2 = 3.075V, and a 150msages down to 0.5V.
minimum reset timeout period. All devices are available intape-and-reel only. There is a 2500-piece minimum order
A variety of push-pull or open-drain reset outputs alongincrement for standard versions (see Table 1). Sample stock iswith manual reset input and power-fail input/output fea-typically held on standard versions only. Nonstandard versionstures are available (see the Selector Guide). Therequire a minimum order increment of 10,000 pieces. ContactMAX6736–MAX6745 are offered in a space-saving 5-pinfactory for availability.
SC70 package and operate over the -40°C to +85°Ctemperature range.
ApplicationsOrdering Information continued at end of data sheet.Portable/Battery-ControllersSelector Guide continued at end of data sheet.Powered EquipmentPDAs
Pin Configurations appear at end of data sheet.
Multivoltage SystemsGPS EquipmentTypical Application Circuits appear at end of data sheet.Notebook Computers
POS Equipment
Functional Diagram appears at end of data sheet.
Selector Guide
PARTVOLTAGEOPEN-DRAINPUSH-PULLMANUALPOWER-FAILPOKRSTINMONITORSRESETRESETRESETINPUT/OUTPUTOUTPUTINPUTMAX67362 fixedX—X———MAX67372 fixed—XX———MAX67381 fixed, 1 adjX—X——X*Manual reset detect on RESEToutput.________________________________________________________________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.
MAX6736–MAX6745元器件交易网www.cecb2b.com
Low-Power Dual-/Triple-Voltage SC70 µPSupervisory CircuitsMAX6736–MAX6745ABSOLUTE MAXIMUM RATINGS
VCC1, VCC2, POK1 to GND......................................-0.3V to +6VOpen-Drain RESET, PFOto GND.............................-0.3V to +6VPush-Pull RESETto GND..........................-0.3V to (VCC1 + 0.3V)MR, RSTIN, PFI to GND............................-0.3V to (VCC1 + 0.3V)Input/Output Current, All Pins.............................................20mAContinuous Power Dissipation (TA= +70°C)
5-Pin SC70 (derate 3.1mW/°C above +70°C)..............247mW
Operating Temperature Range...........................-40°C to +85°CJunction Temperature......................................................+150°CStorage Temperature Range.............................-65°C to +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.
(VCC= 1.2V to 5.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)PARAMETEROperating Voltage RangeSYMBOLVCC1,VCC2CONDITIONSTA = -40°C to 0°CTA = 0°C to +85°CVCC1 = 3.3V, VCC1 > VCC2, no load, resetnot assertedVCC1 = 1.8V, VCC1 < VCC2, no load, resetnot assertedVCC2 = 1.8V, VCC2 < VCC1, no load, resetnot assertedVCC2 = 3.3V, VCC2 > VCC1, no load, resetnot assertedMAX67_ _LMAX67_ _MMAX67_ _TMAX67_ _SReset Threshold for VCC1VTH1MAX67_ _RMAX67_ _ZMAX67_ _YMAX67_ _WMAX67_ _VTA = 0°C to +85°CTA = -40°C to +85°CTA = 0°C to +85°CTA = -40°C to +85°CTA = 0°C to +85°CTA = -40°C to +85°CTA = 0°C to +85°CTA = -40°C to +85°CTA = 0°C to +85°CTA = -40°C to +85°CTA = 0°C to +85°CTA = -40°C to +85°CTA = 0°C to +85°CTA = -40°C to +85°CTA = 0°C to +85°CTA = -40°C to +85°CTA = 0°C to +85°CTA = -40°C to +85°C4.5004.4254.2504.1753.0002.9502.8502.8002.5502.5052.2502.2132.1252.0881.6201.5931.5301.5031.5751.6652.1882.3132.6252.9253.0754.375MIN1.21.0551104.625TYPMAX5.55.510µA102µA204.7504.8254.5004.5753.1503.2003.0003.0502.7002.7452.3752.4132.2502.2881.7101.7371.6201.647VUNITSVELECTRICAL CHARACTERISTICSVCC1 Supply CurrentICC1VCC2 Supply CurrentICC22_______________________________________________________________________________________
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Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(VCC= 1.2V to 5.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSMAX67_ _TTA = 0°C to +85°C3.0003.0753.150TA = -40°C to +85°C2.9053.050MAX67_ _STA = 0°C to +85°C2.8502.9253.000TA = -40°C to +85°C2.8003.050MAX67_ _RTA = 0°C to +85°C2.5502.6252.700TA = -40°C to +85°C2.5052.745MAX67_ _ZTA = 0°C to +85°C2.2502.3132.375TA = -40°C to +85°C2.2132.413MAX67_ _YTA = 0°C to +85°C2.1252.1882.250TA = -40°C to +85°C2.0882.288MAX67_ _WTA = 0°C to +85°C1.6201.6651.710TA = -40°C to +85°C1.5931.737Reset Threshold for VT1.5301.5751.620CC2VTH2MAX67_ _VA = 0°C to +85°CTA = -40°C to +85°C1.5031.647VMAX67_ _ITA = 0°C to +85°C1.3501.3881.425TA = -40°C to +85°C1.3281.448MAX67_ _HTA = 0°C to +85°C1.2751.3131.350TA = -40°C to +85°C1.2531.373MAX67_ _GTA = 0°C to +85°C1.0801.1101.140TA = -40°C to +85°C1.0621.158MAX67_ _FTA = 0°C to +85°C1.0201.0501.080TA = -40°C to +85°C1.0021.098MAX67_ _ETA = 0°C to +85°C0.8100.8330.855TA = -40°C to +85°C0.7970.869MAX67_ _DTA = 0°C to + 85°C0.7650.7880.810TA = -40°C to +85°C0.7520.824RSTIN Threshold (MAX6738/TA = 0°C to +85°C0.4760.4880.500MAX6739/MAX6740/MAX6743)VTH-RSTINTA = -40°C to +85°C0.4680.507VRSTIN Input CurrentVRSTIN ≥ 0.1V (Note 2)-10+10nAReset Threshold HysteresisVTH1, VTH2, RSTIN, PFI0.5%VCC1 ≥ 1.0V, ISINK = 50µA, TA = 0°C to+85°C0.3RESET, POK1 Output LowVOLVCC1 ≥ 1.2V, ISINK = 100µA0.3VVCC1 ≥ 2.13V, ISINK = 1.2mA0.3VCC1 ≥ 4.25V, ISINK = 3.2mA,0.4VCC1 ≥ 2.38V, ISOURCE = 500µA, output0.8 ×RESET Output High (Push-Pull)VdeassertedVCCOHVCC1 ≥ 4.75V, I0.8 ×VSOURCE = 800µA, outputdeassertedVCC_______________________________________________________________________________________3
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Low-Power Dual-/Triple-Voltage SC70 µPSupervisory CircuitsMAX6736–MAX6745ELECTRICAL CHARACTERISTICS (continued)
(VCC= 1.2V to 5.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)PARAMETERRESET Output Open-DrainLeakage Current(MAX6736/MAX6738)POK1 Output Open-DrainLeakageVCC Reset DelayVCC Reset Timeout Period(Note 3)MR to VCC1 Internal PullupImpedanceMR Timeout PeriodMR Minimum Input Pulse WidthMR Glitch RejectionVILMR Input VoltageVIHMR to RESET DelayVCC1 POWER-OK OUTPUT (MAX6741/MAX6744 only)POK1 Timeout PeriodRESET to VCC1 Internal PullupImpedanceManual Reset Detect DebouncePeriodManual Reset TimeoutPeriod (Note 3)Manual Reset Minimum InputPulse WidthManual Reset Release DetectThresholdManual Reset Glitch RejectionManual Reset to RESET DelaytDEBtMRPtMPW(Note 4)MAX67_ _ _ _ XK_ _D3MAX67_ _ _ _ XK_ _ D7(Note 4)(Note 4)(Note 4)tPOKP37.556.2575.0msPUSHBUTTON RESET (MAX6740/MAX6741/MAX6742 only)2537.5150120010.5 ×VCC11003005056.25225180010075.03002400kΩmsmsµsVnsns0.8 ×VCC1300tMRPtMPWBoth D3 and D7 timing optionstRDtRPSYMBOLILKGCONDITIONSOutput not asserted low (Note 2)MINTYPMAX500UNITSnAOutput not asserted low (Note 2)VCC1, VCC2, or RSTIN falling at 10mV/µsfrom VTH + 100mV to VTH - 100mVMAX67_ _ _ _ XK_ _D3MAX67_ _ _ _ XK_ _ D71501200352251800500nAµs3002400msMANUAL RESET (MAX6736–MAX6739 only)0.7515011000.3 ×VCC11.52253.00300kΩmsµsnsVns4_______________________________________________________________________________________
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Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
ELECTRICAL CHARACTERISTICS (continued)
(VCC= 1.2V to 5.5V, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITSPOWER-FAIL COMPARATOR (MAX6742/MAX6745 only)Power Fail In Threshold (Note 5)VTTH-PFIA = 0°C to +85°C0.4760.4880.500TVA = -40°C to +85°C0.4680.507Power Fail In CurrentIPFIVPFI ≥ 0.1V (Note 2)-10+10nAVCC1 ≥ 1.53V, ISINK = 500µA0.3PFO Output LowVOLVCC1 ≥ 2.03V, ISINK = 1.2mA0.3VVCC1 ≥ 4.25V, ISINK = 3.2mA0.4PFI falling at 10mV/µs from VTH-PFI +PFI to PFO Propagation DelaytP100mV to VTH-PFI - 100mV or rising at10mV/µs from VTH-PFI - 100mV to VTH-PFI +35µs100mV (Note 5)PFO Startup DelayTo output valid (Note 5)5msNote 1:All devices are 100% tested at TNote 2:Guaranteed by design.A= +25°C. All temperature limits are guaranteed by design.Note 3:t2 (max) (MAX6741/MAX6744).Note 4:Refers to the manual reset function obtained by forcing the RESET output low.RDtimeout period begins after POK1 timeout period (tPOKP) and VCC2 ≥VTHNote 5:VCC1 ≥1.6V.
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
SUPPLY CURRENT vs. TEMPERATURE
SUPPLY CURRENT vs. TEMPERATURE
101023Vc0octo9CC1 = 3.3V, VCC2 = 2.5V10 t59VCC1 = 2.5V, VCC2 = 1.8V10
45-46-9V0CC1 = 1.8V, VCC2 = 1.2Vcot 54-3667336778X86AXMAM86XA)MA))µ7AA(µµ TOTAL(7(7T N6TTENNRE6E6RIRTOTALRU5CC1RRCUUC5C5TOTAL Y L4YICC1YPLLPP4P4UPPS3UUS3S3ICC12ICC2221I1CC21ICC200
0
-40
-20020406080-40-20020406080
-40
-20
0
20
40
60
80
TEMPERATURE (°C)TEMPERATURE (°C)TEMPERATURE (°C)
_______________________________________________________________________________________5
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Low-Power Dual-/Triple-Voltage SC70 µPSupervisory Circuits45Typical Operating Characteristics (continued)(TA = +25°C, unless otherwise noted.)
76XAM–6376XAM6NORMALIZED VCC/POK1/MR MAXIMUM VCC1/VCC2 TRANSIENT DURATION
TIMEOUT PERIOD vs. TEMPERATURE
vs. RESET THRESHOLD OVERDRIVE
)s1.0194µ10,000
500c(co ottN 554O4--T6I633E7T7S1.0146A6EXRXAARMU RD1000
VCC1M MDT/N1O1.009ERESET OCCURS ABOVEKIIORSETHESE LINESPPN/ ACT1.004RCUT100
V 2 ODECEM0.999CZIV/ITL1A0.994CMCRV 10
VCC2OMN0.989UMIXA0.984
M0-40
-20
0
20
40
60
80
10
100
1000
TEMPERATURE (°C)
RESET THRESHOLD OVERDRIVE (mV)
NORMALIZED VCC RESET THRESHOLD
VCC TO RESET OUTPUT DELAY
vs. TEMPERATURE
vs. TEMPERATURE
1.0086700cocot 5D4-L648.5
100mV OVERDRIVEt 54)-63Os3776Hµ6XA(XS EMYAMR1.003
AHLET D43.5
T ETSUEPR0.998
T CUCO VT38.5
DEESEZIRL AOM0.993
T RCC33.5
ONV NORMALIZED TO +25°C0.988
28.5
-40
-20
0204060
80
-40
-20
0204060
80
TEMPERATURE (°C)
TEMPERATURE (°C)
RESET INPUT TO RESET OUTPUT DELAY
POWER-FAIL INPUT TO POWER-FAIL vs. TEMPERATURE
OUTPUT DELAY vs. TEMPERATURE
3589100mV OVERDRIVE0cot49100mV OVERDRIVE0cot 55)44s--66µ3377(66 YXXAAM)Ls44AMEDµ30
(RISING EDGE TYUAPLTED39UO O TFEPS EORT25
34 IOFTP NITSR29FALLING EDGE 2024-40
-20
0204060
80
-40-20020406080TEMPERATURE (°C)
TEMPERATURE (°C)_______________________________________________________________________________________
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Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
Typical Operating Characteristics (continued)(TA = +25°C, unless otherwise noted.)
POWER-FAIL INPUT TO MR TO RESET OUTPUT DELAY
POWER-FAIL OUTPUT DELAY
MAX6736-45 toc10MAX6736-45 toc11VPFI
MR2V/div
200mV/div
VPFORESET2V/div
2V/div
100ns/div10µs/div
OUTPUT LOW VOLTAGEVCC TO RESET OUTPUT DELAY
vs. SINK CURRENT
MAX6736-45 toc12500
31VcCC = 3.3Vot 54-6376V)CC
V400
XA200mV/divmM( EAC-COUPLED
GATL300
OV WOL T200
UPVTRESETU2V/div
O100
0
4µs/div
0
1
2
3
4
5
6
7
8
9
10
SINK CURRENT (mA)
OUTPUT HIGH VOLTAGEvs. SOURCE CURRENT
4
41VcCC = 3.3Vot 54-6376X)VAM( E3
GATLOV HG2
IH TUPTUO1
00
0.250.500.751.001.251.501.752.00
SOURCING CURRENT (mA)
_______________________________________________________________________________________7
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Low-Power Dual-/Triple-Voltage SC70 µPSupervisory CircuitsMAX6736–MAX6745Pin Description
PINMAX6736MAX6738MAX6740MAX6741MAX6742MAX6737MAX6739MAX6743MAX6744MAX6745NAMEFUNCTIONReset Output, Push-Pull or Open Drain Active Low. RESETchanges from high to low when any monitored power-supplyinput (VCC1, VCC2, RSTIN) drops below its selected resetthreshold. It remains low until all monitored power-supplyinputs exceed their selected reset thresholds for the VCCreset timeout period. RESET is forced low if MR is low for atleast the MR minimum input pulse width. It remains low forthe MR reset timeout period after MR goes high. The push-pull output is referenced to VCC1. The MAX6736/MAX6738open-drain outputs require an external pullup resistor. TheMAX6740/MAX6741/MAX6742 open-drain outputs have aninternal 50kΩ pullup resistor to VCC1 and provide a manualreset function.GroundManual Reset, Active Low. Pull low for at least MR minimuminput pulse width to force RESET low. Reset remains activeas long as MR is low and for the MR reset timeout periodafter MR goes high. There is an internal 1.5kΩ pullup resistorto VCC1.Voltage Input 1. Power supply and input for the secondaryµP voltage reset monitor.Adjustable Reset Threshold Input. RESET is asserted whenRSTIN is below the internal 0.488V reference level. Set theadjustable reset threshold with an external resistor-dividernetwork. Connect RSTIN to VCC1 if unused.Voltage Input 2. Power supply and input for the primary µPvoltage reset monitor.Power-Fail Comparator Input. PFO is asserted when PFI isbelow 0.488V. PFO is deasserted without any reset timeoutperiod when PFI goes above 0.488V. Connect PFI to anexternal resistor network to set the desired monitorthreshold.Power-Fail Comparator Output, Open Drain Active Low. PFOis asserted when PFI is below 0.488V.VCC1 Power-OK Output, Open Drain Active High. POK1remains low as long as VCC1 is below VTH1. POK1 outputgoes high after VCC1 exceeds VTH1 for the POK1 timeoutperiod. POK1 logic is independent of the MR or VCC2 inputs.The output can be used to control VCC1-to-VCC2 supplysequencing.11111RESET22222GND33———MR4—44—VCC2—43——RSTIN55555VCC1————4PFI————3PFO———3—POK18_______________________________________________________________________________________
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Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
Table 1. Reset Voltage Threshold Suffix Guide for MAX6736/MAX6737/MAX6740/MAX6741/MAX6743/MAX6744
PART NO.VCC1 NOMINALVCC2 NOMINALPART NO.VCC1 NOMINALVCC2 NOMINALSUFFIXVOLTAGEVOLTAGESUFFIXVOLTAGEVOLTAGE( _ _ )THRESHOLD (V)THRESHOLD (V)( _ _ )THRESHOLD (V)THRESHOLD (V)LT4.6253.075RD2.6250.788MS4.3752.925ZW2.3131.665MR4.3752.625ZI2.3131.388TZ3.0752.313ZG2.3131.110TW3.0751.665ZE2.3130.833TI3.0751.388YV2.1881.575TG3.0751.110YH2.1881.313TE3.0750.833YF2.1881.050SY2.9252.188YD2.1880.788SV2.9251.575WT1.6653.075SH2.9251.313WI1.6651.388SF2.9251.050WG1.6651.110SD2.9250.788WE1.6650.833RY2.6252.188VR1.5752.625RV2.6251.575VH1.5751.313RH2.6251.313VF1.5751.050RF2.6251.050VD1.5750.788Note: Standard versions, shown in bold, are available in the D3 timeout option only. Samples are typically held on standard versionsonly. There is a 10,000-piece order increment on nonstandard versions. Other threshold voltage combinations may be available;contact factory for availability.
Table 2. Reset Voltage Threshold SuffixGuide for MAX6738/MAX6739/MAX6742/Table 3. VCCTimeout Period SuffixMAX6745
Guide
PART NO.VCC1 NOMINALTIMEOUT ACTIVE TIMEOUT PERIODSUFFIXVOLTAGEPERIOD( _ )THRESHOLD (V)SUFFIXMIN (ms)MAX (ms)L4.625D3150300M4.375D712002400T3.075S2.925R2.625Z2.313Y2.188W1.665V1.575Note:Standard versions, shown in bold, are available in theD3 timeout option only. Samples are typically held on standardversions only. There is a 10,000-piece order increment on non-standard versions. Other threshold voltages may be avail-able; contact factory for availability._______________________________________________________________________________________9
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Low-Power Dual-/Triple-Voltage SC70 µPSupervisory CircuitsMAX6736–MAX6745VCC1VTH1GNDPOK1tPOKPGNDVCC2VTH2GNDMRSWITCHBOUNCESWITCHBOUNCEGNDRESETtRPGNDtMRPFigure 1. Timing Diagram
Detailed DescriptionSupply Voltages
The MAX6736–MAX6745 µP supervisory circuits main-tain system integrity by alerting the µP to fault condi-tions. These devices are optimized for systems thatmonitor two or three supply voltages. The reset outputstate is guaranteed to remain valid while either VCC1 orVCC2 is above 1.2V.
Reset Output
The MAX6736–MAX6745 provide an active-low reset out-put (RESET). RESETis asserted when the voltage ateither VCC1 or VCC2 falls below the voltage thresholdlevel, RSTIN drops below the threshold, or MRis pulledlow. Once reset is asserted, it stays low for the reset time-out period. If VCC1, VCC2, or RSTIN goes below the resetthreshold before the reset timeout period is completed,the internal timer restarts. The MAX6736/MAX6738/MAX6740/MAX6741/MAX6742 have open-drain reset out-puts, while the MAX6737/MAX6739/MAX6743/MAX6744/MAX6745 have push-pull reset outputs (Figure 1).
The MAX6740/MAX6741/MAX6742 include a RESEToutput with a manual reset detect function. The open-drain RESEToutput has an internal 50kΩpullup toVCC1. The RESEToutput is low while the output ispulled to GND and remains low for at least the manualreset timeout period after the external GND pulldown is
Threshold Levels
The MAX6736/MAX6737/MAX6740/MAX6741/MAX6743/MAX6744 input voltage threshold combinations are indi-cated by a two-letter code in Table 1. The MAX6738/MAX6739/MAX6742/MAX6745 input voltage thresholdsare indicated by a one-letter code in Table 2. Contact thefactory for the availability of other voltage thresholds.
10______________________________________________________________________________________
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Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
SWITCHSWITCHSWITCHSWITCHBOUNCEBOUNCEBOUNCEBOUNCEOPENPUSHBUTTONSWITCHCLOSEDVCC1tDEBtMRPtDEBtMRPRESETGNDFigure 2. MAX6740/MAX6741/MAX6742 Manual Reset Timing Diagram
released. The manual reset detect function is internallycally 488mV. Connect a resistor-divider network to thedebounced for the tcircuit as shown in Figure 3 to establish an externallycan be connected directly to a momentary pushbuttonDEBtimeout period, so the outputcontrolled threshold voltage, Vswitch, if desired (Figure 2).
EXT_TH.
VEXT_TH= 0.488V((R1 + R2) / R2)
Manual Reset Input
Many microprocessor-based products require manualLow leakage current at RSTIN allows the use of large-reset capability, allowing the operator, a test techni-valued resistors, resulting in reduced power consump-cian, or external logic circuitry to initiate a reset whiletion of the system.
the monitored supplies remain above their reset thresh-Power-Fail Comparator
olds. The MAX6736–MAX6739 have a dedicatedPFI is the noninverting input to an auxiliary comparator. Aactive-low MRinput. The RESETis asserted low while488mV internal reference (VMRis held low and remains asserted for the manualinverting input of the comparator. If PFI is less thanTH-PFI) is connected to thereset timeout period after MRreturns high. The MR488mV, PFOis asserted low. PFOdeasserts without ainput has an internal 1.5kΩpullup resistor to VCC1andtimeout period when PFI rises above the externally setcan be left unconnected if not used. MRcan be driventhreshold. Common uses for the power-fail comparatorwith CMOS logic levels, open-drain/open-collector out-include monitoring for low battery conditions or a failingputs, or a momentary pushbutton switch to GND to cre-DC-DC converter input voltage (see the Typicalate a manual reset function.
Application Circuits). The asserted PFOoutput can placeAdjustable Input Voltage
a system in a low-power suspend mode or support anThe MAX6738/MAX6739 and MAX6740/MAX6743 pro-orderly system shutdown before monitored VCCvoltagesvide an additional input to monitor a second or thirddrop below the reset thresholds. Connect PFI to an exter-system voltage. The threshold voltage at RSTIN is typi-
nal resistor-divider network as shown in Figure 4 to setthe desired trip threshold. Connect PFI to VCC1 if unused.
Applications Information
Interfacing to the µP withVEXT_THMAX6738Bidirectional Reset Pins
Most microprocessors with bidirectional reset pins canR1MAX6739MAX6740interface directly to open-drain RESEToutput options.Systems simultaneously requiring a push-pull RESETRSTINMAX6743output and a bidirectional reset interface can be inR2logic contention. To prevent contention, connect a4.7kΩresistor between RESETand the µP’s reset I/Oport as shown in Figure 5.
GNDFigure 3. Monitoring an Additional Voltage
______________________________________________________________________________________
11
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Low-Power Dual-/Triple-Voltage SC70 µPSupervisory CircuitsMAX6736–MAX6745A) VIN IS POSITIVEVEXT_THR1PFIR2MAX6742MAX6745PFOVEXT_TH = VTH-PFI(R1 + R2R2)GNDshown in Figure 6. Select the values of R1, R2, and R3such that PFI sees VTH-PFI(488mV) when VEXTfalls toits power-fail trip point (VFAIL) and when VEXTrises toits power-good trip point (VGOOD). The hysteresis win-dow extends between the specified VFAILand VGOODthresholds. R3 adds the additional hysteresis by sink-ing current from the R1/R2 divider network when thePFOoutput is logic low and sourcing current into thenetwork when PFOis logic high. R3 is typically an orderof magnitude greater than R1 or R2.
The current through R2 should be at least 1µA to ensurethat the 10nA (max) PFI input current does not significant-ly shift the trip points. Therefore, for most applications:
R2 < VTH-PFI/ 1mA < 0.488V / 1mA < 488kΩ
B) VIN IS NEGATIVEVCCR1PFIR2MAX6742MAX6745PFOVEXT_TH = R2 (( )(VTH-PFI)V1+1-CCR1R1R2)VPFI = 488mVPFOis an open-drain output requiring an external
pullup resistor, R4. Select R4 to be less than 1% of R3.VGOOD= DESIRED VEXTGOOD VOLTAGE THRESHOLDVFAIL= DESIRED VEXTFAIL VOLTAGE THRESHOLDVPU= VPULLUP(FOR OPEN-DRAIN PFO)R2 = 488kΩ(FOR >1µA R2 CURRENT)
VEXT_THGNDFigure 4. Using Power-Fail Input to Monitor an AdditionalPower Supply
R1=R2 (VGOOD-VTH−PFI − )(VTH-PFI(VGOOD-VFAIL)VPUVTH-PFIAdding Hysteresis to thePower-Fail Comparator
The power-fail comparator has a typical input hystere-sis of 2.5mV. This is sufficient for most applications inwhich a power-supply line is being monitored throughan external voltage-divider. If additional noise margin isdesired, connect a resistor between PFOand PFI, as
R3 = (R1 x VPU) / (VGOOD- VFAIL)R4 ≤0.01 x R3
Power Sequencing Applications
Many dual-voltage processors/ASICs require specificpower-up/power-down sequences for the I/O and coresupplies.
VCC1VCC2RESET TO OTHER SYSTEM COMPONENTSR3VPULLUPVGOODVFAILVINVCC2VCC1MAX6737MAX6739MAX6743MAX6744RESETMAX6745VEXTMAX6742MAX6745R1PFIR2PFOR4PFO4.7kΩRESETµPGNDGNDGNDVGOOD = DESIRED VEXT GOOD VOLTAGE THRESHOLDVFAIL = DESIRED VEXT FAIL VOLTAGE THRESHOLDVOH = VCC1 (FOR PUSH-PULL PFO)R2 = 200kΩ (FOR > 2.5µA R2 CURRENT)R1 = R2 ((VGOOD - VTH-PFI) - (VTH-PFI)(VGOOD - VFAIL) / VPU) / VTH-PFIR3 = (R1 x VOH) / (VGOOD - VFAIL)Figure 5. Interfacing to µPs with Bidirectional Reset I/O12
Figure 6. Adding Hysteresis to Power Fail for Push-Pull PFO______________________________________________________________________________________
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Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
The MAX6741/MAX6744 offer a VCC1 POK (POK1) idealTransient Immunity
for VThe MAX6736–MAX6745 supervisors are relativelylong as VCC1-to-V1 is below its VCC2 sequencing. POK1 remains low asCCTH1 threshold. When VCC1immune to short-duration falling Vexceeds Ves). It is usually undesirable to reset the µP when VCCtransients (glitch-open-drain POK1 output is deasserted. The POK1 outputTH1 for the POK1 timeout period (tPOKP), theexperiences only small glitches. The Typical OperatingCCcan then enable the VCharacteristics show Maximum VPOK1 pullup resistor). CC2 power supply (use an externalRESETis deasserted when bothCC1/VCC2TransientDuration vs. Reset Threshold Overdrive, for which resetVCC1 and VCC2 remain above their selected thresholdspulses are not generated. The graph shows the maxi-for the reset timeout period (tmum pulse width that a falling Vbe used for I/O before core or core before I/O sequenc-RP). The POK1 output canCCtransient might typi-cally have without causing a reset pulse to be issued.ing, depending on the selected VAs the amplitude of the transient increases, the maxi-See the Typical Application Circuit CC1/Vand Figure 1.
CC2 thresholds.mum allowable pulse width decreases. A 0.1µF bypassMonitoring a Negative Voltage
capacitor mounted close to the VCCpin provides addi-The power-fail comparator can be used to monitor ational transient immunity.
negative supply voltage using the circuit shown inFigure 4. When the negative supply is valid, PFOis low.When the negative supply voltage drops, PFOgoesChip Information
high. The circuit’s accuracy is affected by the PFITRANSISTOR COUNT: 249threshold tolerance, VCC, R1, and R2.
PROCESS: BiCMOS
Functional Diagram
VCC1MAX6736–MAX6745PFODELAYPOK1VCC1VCC2RSTIN/PFIRESETTIMEOUTRESETPERIODOUTPUTRESETVCC2VCC1MRPULLUP0.488VVCC11.23VMR______________________________________________________________________________________13MAX6736–MAX6745元器件交易网www.cecb2b.com
Low-Power Dual-/Triple-Voltage SC70 µPSupervisory CircuitsMAX6736–MAX6745Selector Guide (continued)
PARTMAX6739MAX6740MAX6741MAX6742MAX6743MAX6744MAX6745VOLTAGEMONITORS1 fixed, 1 adj2 fixed, 1 adj2 fixed1 fixed2 fixed, 1adj2 fixed1 fixedOPEN-DRAINRESET—X*X*X*———PUSH-PULLRESETX———XXXMANUALRESETXX*X*X*———POWER-FAILINPUT/OUTPUT———X——XPOKOUTPUT——X——X—RSTININPUTXX——X——*Manual reset detect on RESEToutput.Typical Application CircuitsDC/DCCONVERTERUNREGULATEDDCINOUTVBATTINOUTDC/DCCONVERTERVCC1VCC2VCC1COREI/OSUPPLYSUPPLYµPINOUTDC/DCCONVERTERSHDNPFOMAX6742VCCµPPFIGNDRESETMAX6741RESETGNDPOK1GNDRESETRESETGNDPUSHBUTTONSWITCHPUSHBUTTONSWITCH14______________________________________________________________________________________
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Low-Power Dual-/Triple-Voltage SC70 µP
Supervisory Circuits
Pin Configurations
TOP VIEWRESET15VCC1RESET15VCC1RESET15VCC1MAX6740GND2MAX6736MAX6737GND2MAX6738MAX6739GND2MAX6743MR34VCC2MR34RSTINRSTIN34VCC2SC70SC70SC70RESET15VCC1RESET15VCC1GND2MAX6741MAX6744GND2MAX6742MAX6745POK134VCC2PFO34PFISC70SC70Ordering Information (continued)PARTTEMP RANGEPIN-PACKAGEMAX6738XK_D_-T-40°C to +85°C5 SC70-5MAX6739XK_D_-T-40°C to +85°C5 SC70-5MAX6740XK_ _D_-T-40°C to +85°C5 SC70-5MAX6741XK_ _D_-T-40°C to +85°C5 SC70-5MAX6742XK_D_-T-40°C to +85°C5 SC70-5MAX6743XK_ _D_-T-40°C to +85°C5 SC70-5MAX6744XK_ _D_-T-40°C to +85°C5 SC70-5MAX6745XK_D_-T-40°C to +85°C5 SC70-5______________________________________________________________________________________15
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Low-Power Dual-/Triple-Voltage SC70 µPSupervisory CircuitsMAX6736–MAX6745Package 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.)SC70, 5L.EPSMaxim 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.
16____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600©2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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