MAX1668MEE+T资料

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元器件交易网www.cecb2b.com19-1766; Rev 2; 5/03

Multichannel Remote/Local

Temperature Sensors

________________General Description

____________________________Features

The MAX1668/MAX1805/MAX19 are precise multi-channel digital thermometers that report the tempera-oMultichannel

ture of all remote sensors and their own packages. The4 Remote, 1 Local (MAX1668/MAX19)remote sensors are diode-connected transistors—typi-2 Remote, 1 Local (MAX1805)cally low-cost, easily mounted 2N3904 NPN types—thatoNo Calibration Requiredreplace conventional thermistors or thermocouples.Remote accuracy is ±3°C for multiple transistor manu-oSMBus 2-Wire Serial Interface

facturers, with no calibration needed. The remote chan-oProgrammable Under/Overtemperature Alarmsnels can also measure the die temperature of other ICs,such as microprocessors, that contain an on-chip,oSupports SMBus Alert Responsediode-connected transistor.

oAccuracy

The 2-wire serial interface accepts standard system±2°C (+60°C to +100°C, Local)management bus (SMBus™) write byte, read byte, send±3°C (-40°C to +125°C, Local)byte, and receive byte commands to program the alarm±3°C (+60°C to +100°C, Remote)thresholds and to read temperature data. The data for-mat is 7 bits plus sign, with each bit corresponding too3µA (typ) Standby Supply Current1°C, in two’s-complement format.

o700µA (max) Supply Current

The MAX1668/MAX1805/MAX19 are available insmall, 16-pin QSOP surface-mount packages. TheoSmall, 16-Pin QSOP/TSSOP Packages

MAX19 is also available in a 16-pin TSSOP.

_______________Ordering Information________________________Applications

PARTTEMP RANGEPIN-PACKAGEDesktop and NotebookCentral-Office TelecomMAX1668MEE-55°C to +125°C16 QSOPComputersEquipment

MAX1805MEE-55°C to +125°C16 QSOPLAN ServersTest and MeasurementMAX19MEE-55°C to +125°C16 QSOPIndustrial Controls

Multichip Modules

MAX19MUE-55°C to +125°C16 TSSOPPin ConfigurationTypical Operating Circuit0.1µF3V TO 5.5VTOP VIEW200ΩDXP1116GNDVCCSTBYDXN1215STBY10kΩ EACHMAX1668DXP2314SMBCLKMAX1805MAX19DXN24MAX1668DXP1SMBCLKCLOCK2200pF(N.C.) DXP35MAX180513SMBDATAMAX1912ALERT*DXN1SMBDATADATA(N.C.) DXN3611ADD0ALERTINTERRUPTTO µC(N.C.) DXP4710ADD1DXP4(N.C.) DXN4VCC2200pF*DXN4QSOP/TSSOPADD0ADD1GND( ) ARE FOR MAX1805.* DIODE-CONNECTED TRANSISTORSMBus is a trademark of Intel Corp.

†Patents Pending

________________________________________________________________Maxim Integrated Products

For pricing, delivery, and ordering information,please contact Maxim/Dallas Direct!at 1-888-629-42, or visit Maxim’s website at www.maxim-ic.com.

MAX1668/MAX1805/MAX19†元器件交易网www.cecb2b.comMultichannel Remote/Local Temperature SensorsMAX1668/MAX1805/MAX19†ABSOLUTE MAXIMUM RATINGS

VCCto GND..............................................................-0.3V to +6V DXP_, ADD_, STBY to GND........................-0.3V to (VCC+ 0.3V)DXN_ to GND........................................................-0.3V to +0.8VSMBCLK, SMBDATA, ALERTto GND......................-0.3V to +6VSMBDATA, ALERTCurrent.................................-1mA to +50mADXN_ Current......................................................................±1mAContinuous Power Dissipation (TA= +70°C)

QSOP (derate 8.30mW/°C above +70°C)....................667mWTSSOP (derate 9.40mW/°C above +70°C)..................755mW

Operating Temperature Range.........................-55°C to +125°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.

ELECTRICAL CHARACTERISTICS

(VCC= +3.3V, STBY= VCC, configuration byte = X0XXXX00, TA= 0°C to +125°C, unless otherwise noted.)

PARAMETERADC AND POWER SUPPLYTemperature Resolution (Note 1)Initial Temperature Error,Local Diode (Note 2)Temperature Error, Remote Diode(Notes 2, 3)Temperature Error, Local Diode(Notes 1, 2)Supply Voltage RangeUndervoltage Lockout ThresholdUndervoltage Lockout HysteresisPower-On Reset (POR) ThresholdPOR Threshold HysteresisStandby Supply CurrentLogic inputsforced to VCCor GNDSMBus staticHardware or software standby,SMBCLK at 10kHzVCC, falling edge1.3VCCinput, disables A/D conversion, rising edgeMonotonicity guaranteedTA = +60°C to +100°CTA = 0°C to +125°CTR = +60°C to +100°CTR = -55°C to +125°CIncluding long-term driftTA = +60°C to +100°CTA = 0°C to +85°C8-2-3-3-5-2.5-3.53.02.602.8501.8503540026070732010010200500.7ADD0, ADD1; momentary upon power-on reset160VµA10µA1270038013013µAµAms2.3+2+3+3+5+2.5+3.55.52.95Bits°C°C°CVVmVVmVCONDITIONSMINTYPMAXUNITSAverage Operating Supply CurrentConversion TimeAverage measured over 4s; logic inputs forced VCCor GNDFrom stop bit to conversion complete (all channels)High level (POR state)Low level (POR state)Configuration byte =X0XXXX10, high levelConfiguration byte =X0XXXX01, high levelRemote-Diode Source CurrentDXP_ forced to 1.5VDXN_ Source VoltageAddress Pin Bias Current2_______________________________________________________________________________________

元器件交易网www.cecb2b.comMultichannel Remote/Local

Temperature Sensors

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3.3V, STBY= VCC, configuration byte = X0XXXX00, TA= 0°C to +125°C, unless otherwise noted.)

PARAMETERSMBus INTERFACELogic Input High VoltageLogic Input Low VoltageLogic Output Low Sink CurrentALERTOutput High LeakageCurrentLogic Input CurrentSMBus Input CapacitanceSMBus Clock FrequencySMBCLK Clock Low TimeSMBCLK Clock High TimeSMBus Start-Condition Setup TimeSMBus Repeated Start-ConditionSetup TimeSMBus Start-Condition Hold TimeSMBus Stop-Condition Setup TimeSMBus Data Valid to SMBCLKRising-Edge TimeSMBus Data-Hold TimeSMBCLK Falling Edge to SMBustSU:STA, 90% to 90% pointstHD:STA, 10% of SMBDATA to 90% of SMBCLKtSU:STO, 90% of SMBCLK to 10% of SMBDATAtSU:DAT, 10% or 90% of SMBDATA to 10% of SMBCLKtHD:DAT, slave receive (Note 5)STBY, SMBCLK, SMBDATA; VCC= 3V to 5.5VSTBY, SMBCLK, SMBDATA; VCC= 3V to 5.5VALERT,SMBDATA forced to 0.4VALERTforced to 5.5VLogic inputs forced to VCCor GNDSMBCLK, SMBDATA(Note 4)tLOW, 10% to 10% pointstHIGH, 90% to 90% pointsDC4.744.7250442500-1510061+12.20.8VVmAµAµApFkHzµsµsµsnsµsµsnsnsCONDITIONSMINTYPMAXUNITSMAX1668/MAX1805/MAX19Data-Valid TimeMaster clocking in data1µsELECTRICAL CHARACTERISTICS

(VCC= +5V, STBY= VCC, configuration byte = X0XXXX00, TA= -55°C to +125°C, unless otherwise noted.) (Note 6)

PARAMETERCONDITIONSMINTYPMAXUNITSADC AND POWER SUPPLYTemperature ResolutionMonotonicity guaranteed8BitsInitial Temperature Error, TA= +60°C to +100°C-2+2Local Diode (Note 2)TA= -55°C to +125°C-3+3°CTemperature Error, Remote DiodeTR= +60°C to +100°C-3+3(Notes 2, 3)TR= -55°C to +125°C-5+5°CSupply-Voltage Range4.55.5VConversion TimeFrom stop bit to conversion complete (both channels)260380ms_______________________________________________________________________________________3

†元器件交易网www.cecb2b.comMultichannel Remote/Local Temperature SensorsMAX1668/MAX1805/MAX19†ELECTRICAL CHARACTERISTICS (continued)

(VCC= +5V, STBY= VCC, configuration byte = X0XXXX00, TA= -55°C to +125°C, unless otherwise noted.) (Note 6)

PARAMETERSMBus INTERFACELogic Input High VoltageLogic Input Low VoltageLogic Output Low Sink CurrentALERTOutput High LeakageCurrentLogic Input CurrentSTBY, SMBCLK, SMBDATA; VCC= 4.5V to 5.5VSTBY, SMBCLK, SMBDATA; VCC= 4.5V to 5.5VALERT,SMBDATA forced to 0.4VALERTforced to 5.5VLogic inputs forced to VCCor GND-261+22.40.8VVmAµAµACONDITIONSMINTYPMAXUNITSNote 1:Guaranteed by design, but not production tested.

Note 2:Quantization error is not included in specifications for temperature accuracy. For example, if the MAX1668/MAX1805/

MAX19 device temperature is exactly +66.7°C, the ADC may report +66°C, +67°C, or +68°C (due to the quantizationerror plus the +0.5°C offset used for rounding up) and still be within the guaranteed ±1°C error limits for the +60°C to+100°C temperature range. See Table 2.

Note 3:A remote diode is any diode-connected transistor from Table 1. TRis the junction temperature of the remote diode. See the

Remote-Diode Selectionsection for remote-diode forward-voltage requirements.

Note 4:The SMBus logic block is a static design that works with clock frequencies down to DC. While slow operation is possible, it

violates the 10kHz minimum clock frequency and SMBus specifications, and can monopolize the bus.

Note 5:Note that a transition must internally provide at least a hold time in order to bridge the undefined region (300ns max) of

SMBCLK’s falling edge tHD:DAT.

Note 6:Specifications from -55°C to +125°C are guaranteed by design, not production tested.

Typical Operating Characteristics(Typical Operating Circuit, VCC= +5V, STBY= VCC, configuration byte = X0XXXX00, TA = +25°C, unless otherwise noted.)

TEMPERATURE ERRORvs. PC BOARD RESISTANCE

MAX1668/1805 toc01TEMPERATURE ERRORvs. TEMPERATURE

MAX1668/1805 toc02TEMPERATURE ERRORvs. SUPPLY NOISE FREQUENCY

WITH VCC 0.1µF CAPACITOR REMOVED2200pF BETWEEN DXN_ AND DXP_250mVP-P16128400.1

100

FREQUENCY (MHz)

MAX1668/1805 toc032043TEMPERATURE ERROR (°C)NPN (CMPT3904)210-1

INTERNALPNP (CMPT3906)2420TEMPERATURE ERROR (°C)TEMPERATURE ERROR (°C)10

PATH = DXP_ TO GND0

-10

PATH = DXP_ TO VCC (5V)100mVP-P-20

LEAKAGE RESISTANCE (MΩ)

100

-2

-50-30-10

110

TEMPERATURE (°C)

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Temperature Sensors

Typical Operating Characteristics (continued)(Typical Operating Circuit, VCC= +5V, STBY= VCC, configuration byte = X0XXXX00, TA = +25°C, unless otherwise noted.)

TEMPERATURE ERROR

STANDBY SUPPLY CURRENTvs. COMMON-MODE NOISE FREQUENCY

vs. DXP_ TO DXN_ CAPACITANCE

vs. CLOCK FREQUENCY

2.0460

6050SQUARE-WAVE AC-COUPLED INTO DXNc40occo1.8to tt5 52200pF BETWEEN DXN_ AND DXP_05STBY = GND08012881/1/88866666506)1.611)1CXXACAXM°M)A°(AM( R1.4100mVP-P R0µO(O RRT40RRNE1.2EE E RRE-2RRU1.050mVP-PUUTTC30 AYVRA-4CC = 5VLE0.8RPPEPM0.6PM-6U20

ESTET0.4VCC = 3.3V-8100.20-10

0.1

10100100001020304050601101001000

FREQUENCY (MHz)

DXP_ TO DXN_ CAPACITANCE (nF)SMBCLK FREQUENCY (kHz)

STANDBY SUPPLY CURRENTvs. SUPPLY VOLTAGE

RESPONSE TO THERMAL SHOCK

1607800STBY = GND125

ccoott 55140008811//ADD0 = ADD1 = GND88610066611XX)AAA120MMµ)(C T°(N EE100RR75

RUUTC80AR YELPPM50

P60EUTS40ADD0 = ADD1 = HIGH-Z25

2016 QSOP IMMERSED IN+115°C FLUORINERT BATH00

1234

-2

SUPPLY VOLTAGE (V)

TIME (s)

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MAX1668/MAX1805/MAX19†元器件交易网www.cecb2b.comMultichannel Remote/Local Temperature SensorsMAX1668/MAX1805/MAX19†Pin DescriptionPINMAX1668/MAX191, 3, 5, 72, 4, 6, 10111213141516MAX1805NAMEFUNCTIONCombined Current Source and A/D Positive Input for Remote-Diode Channel. Do notleave DXP floating; connect DXP to DXN if no remote diode is used. Place a 2200pFcapacitor between DXP and DXN for noise filtering.Combined Current Sink and A/D Negative Input. DXN is normally biased to a diode volt-age above ground. Supply Voltage Input, 3V to 5.5V. Bypass to GND with a 0.1µF capacitor. A 200Ωseriesresistor is recommended but not required for additional noise filtering.SMBus Address Select Pin (Table 8). ADD0 and ADD1 are sampled upon power-up.Excess capacitance (>50pF) at the address pins when floating can cause address-recognition problems.SMBus Slave Address Select PinSMBus Alert (Interrupt) Output, Open DrainSMBus Serial-Data Input/Output, Open DrainSMBus Serial-Clock InputHardware Standby Input. Temperature and comparison threshold data are retained instandby mode. Low = standby mode, high = operate mode.GroundNo Connection. Not internally connected. Can be used for PC board trace routing.1, 32, 49101112131415165–8DXP_DXN_VCCADD1ADD0ALERTSMBDATASMBCLKSTBYGNDN.C.—_______________Detailed Description

The MAX1668/MAX1805/MAX19 are temperaturesensors designed to work in conjunction with an exter-nal microcontroller (µC) or other intelligence in thermo-static, process-control, or monitoring applications. TheµC is typically a power-management or keyboard con-troller, generating SMBus serial commands by “bit-banging” general-purpose input-output (GPIO) pins orthrough a dedicated SMBus interface block.

These devices are essentially 8-bit serial analog-to-digi-tal converters (ADCs) with sophisticated front ends.However, the MAX1668/MAX1805/MAX19 also containa switched current source, a multiplexer, an ADC, anSMBus interface, and associated control logic (Figure 1).In the MAX1668 and MAX19, temperature data fromthe ADC is loaded into five data registers, where it isautomatically compared with data previously stored in10 over/undertemperature alarm registers. In theMAX1805, temperature data from the ADC is loaded intothree data registers, where it is automatically comparedwith data previously stored in six over/undertemperaturealarm registers.

ADC and Multiplexer

The ADC is an averaging type that integrates over ams period (each channel, typical), with excellentnoise rejection.

The multiplexer automatically steers bias currentsthrough the remote and local diodes, measures theirforward voltages, and computes their temperatures.Each channel is automatically converted once the con-version process has started. If any one of the channelsis not used, the device still performs measurements onthese channels, and the user can ignore the results ofthe unused channel. If any remote-diode channel isunused, connect DXP_ to DXN_ rather than leaving thepins open.

The DXN_ input is biased at 0.65V above ground by aninternal diode to set up the A/D inputs for a differentialmeasurement. The worst-case DXP_ to DXN_ differentialinput voltage range is 0.25V to 0.95V.

Excess resistance in series with the remote diode caus-es about +0.5°C error per ohm. Likewise, 200µV of offsetvoltage forced on DXP_ to DXN_causes about 1°C error.

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Temperature Sensors

ATKTALRDCEBBLMMASSQ1DSRDSEsAEDuR RB O DCDDEMSDADSA YBLTOSRCITGNOOLCRSERTEESTTISYERGIEEGBS TRENNS RROIE OGTEIEPEYT2TTS ASERBYDRI BD NSUGR SAETKNS GRREAU1ISFERNLARCMTAOADDMET DCATSIAMTSORGCEELRA.98X9US1MRXAETEDLTSMOUIS IRSSDDAGFEERRNRTE ASTOA IST8TGIA6AEGR6DREA1 RES PXRTSMAUITTMIOM IMCRALI LLOTSRH AF NELEGWTEIECAPIRRMHOLGRIARCED SUUOTECOLSNIL DETTOD :ETON443221PNP3XXXNPNP1DDDXXXXNDDDDXDFigure 1. MAX1668/MAX1805/MAX19 Functional Diagram

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MAX1668/MAX1805/MAX19†元器件交易网www.cecb2b.comMultichannel Remote/Local Temperature SensorsMAX1668/MAX1805/MAX19†A/D Conversion Sequence

If a start command is written (or generated automaticallyin the free-running autoconvert mode), all channels areconverted, and the results of all measurements areavailable after the end of conversion. A BUSY status bitin the status byte shows that the device is actually per-forming a new conversion; however, even if the ADC isbusy, the results of the previous conversion are alwaysavailable.

Table 1. Remote-Sensor TransistorManufacturers

MANUFACTURERCentral Semiconductor (USA)Motorola (USA)National Semiconductor (USA)Rohm Semiconductor (Japan)Samsung (Korea)Siemens (Germany)Zetex (England)MODEL NO.CMPT3904MMBT3904MMBT3904SST3904KST3904-TFSMBT3904FMMT3904CT-NDRemote-Diode Selection

Temperature accuracy depends on having a good-qual-ity, diode-connected small-signal transistor. Accuracyhas been experimentally verified for all of the deviceslisted in Table 1. The MAX1668/MAX1805/MAX19 canalso directly measure the die temperature of CPUs andother ICs having on-board temperature-sensing diodes.The transistor must be a small-signal type, either NPNor PNP, with a relatively high forward voltage; other-wise, the A/D input voltage range can be violated. Theforward voltage must be greater than 0.25V at 10µA;check to ensure this is true at the highest expectedtemperature. The forward voltage must be less than0.95V at 100µA; check to ensure this is true at the low-est expected temperature. Large power transistors donot work at all. Also, ensure that the base resistance isless than 100Ω. Tight specifications for forward-currentgain (+50 to +150, for example) indicate that the manu-facturer has good process controls and that thedevices have consistent VBE characteristics.

For heat-sink mounting, the 500-32BT02-000 thermalsensor from Fenwal Electronics is a good choice. Thisdevice consists of a diode-connected transistor, an aluminum plate with screw hole, and twisted-pair cable(Fenwal Inc., Milford, MA, 508-478-6000).

Note:Transistors must be diode connected (base shorted tocollector).

worst-case error occurs when sinking maximum currentat the ALERToutput. For example, with ALERTsinking1mA, the typical power dissipation is VCCx 400µA plus0.4V x 1mA. Package theta J-A is about 150°C/W, sowith VCC= 5V and no copper PC board heat sinking,the resulting temperature rise is:

dT = 2.4mW x 150°C/W = 0.36°C

Even with these contrived circumstances, it is difficultto introduce significant self-heating errors.

ADC Noise Filtering

The ADC is an integrating type with inherently goodnoise rejection, especially of low-frequency signals suchas 60Hz/120Hz power-supply hum. Micropower opera-tion places constraints on high-frequency noise rejec-tion; therefore, careful PC board layout and properexternal noise filtering are required for high-accuracyremote measurements in electrically noisy environments. High-frequency EMI is best filtered at DXP_ and DXN_with an external 2200pF capacitor. This value can beincreased to about 3300pF (max), including cablecapacitance. Higher capacitance than 3300pF intro-duces errors due to the rise time of the switched cur-rent source.

Nearly all noise sources tested cause additional errormeasurements, typically by +1°C to +10°C, dependingon the frequency and amplitude (see the TypicalOperating Characteristics).

Thermal Mass and Self-Heating

Thermal mass can seriously degrade the MAX1668/MAX1805/MAX19s’ effective accuracy. The thermaltime constant of the 16-pin QSOP package is about140s in still air. For the MAX1668/MAX1805/MAX19junction temperature to settle to within +1°C after asudden +100°C change requires about five time con-stants or 12 minutes. The use of smaller packages forremote sensors, such as SOT23s, improves the situa-tion. Take care to account for thermal gradientsbetween the heat source and the sensor, and ensurethat stray air currents across the sensor package donot interfere with measurement accuracy.

Self-heating does not significantly affect measurementaccuracy. Remote-sensor self-heating due to the diodecurrent source is negligible. For the local diode, the

PC Board Layout

1)Place the MAX1668/MAX1805/MAX19 as close as

practical to the remote diode. In a noisy environment,such as a computer motherboard, this distance can

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Temperature Sensors

be 4in to 8in (typ) or more as long as the worst noisesources (such as CRTs, clock generators, memoryGNDbuses, and ISA/PCI buses) are avoided.

10mils2)Do not route the DXP_ to DXN_ lines next to the

deflection coils of a CRT. Also, do not route the10milsDXP_traces across a fast memory bus, which can easilyMINIMUMintroduce +30°C error, even with good filtering.Otherwise, most noise sources are fairly benign.10milsDXN_3)Route the DXP_ and DXN_ traces in parallel and in

10milsclose proximity to each other, away from any high-GNDvoltage traces such as +12VDC. Leakage currentsfrom PC board contamination must be dealt withFigure 2. Recommended DXP_/DXN_ PC Traces

carefully, since a 20MΩleakage path from DXP_ toground causes about +1°C error.

•Place the noise filter and the 0.1µF VCCbypass4)Connect guard traces to GND on either side of the

capacitors close to the MAX1668/MAX1805/DXP_ to DXN_ traces (Figure 2). With guard tracesMAX19.

in place, routing near high-voltage traces is no•Add a 200Ωresistor in series with Vlonger an issue. filtering (see the Typical Operating CircuitCCfor best noise).

5)Route through as few vias and crossunders as possi-Twisted-Pair and Shielded Cables

ble to minimize copper/solder thermocouple effects. For remote-sensor distances longer than 8in, or in partic-6)When introducing a thermocouple, make sure that

ularly noisy environments, a twisted pair is recommend-both the DXP_ and the DXN_ paths have matchinged. Its practical length is 6ft to 12ft (typ) before noisethermocouples. In general, PC board-induced ther-becomes a problem, as tested in a noisy electronics lab-mocouples are not a serious problem. A copper-sol-oratory. For longer distances, the best solution is ader thermocouple exhibits 3µV/°C, and it takesshielded twisted pair like that used for audio micro-about 200µV of voltage error at DXP_ to DXN_ tophones. For example, Belden #8451 works well for dis-cause a +1°C measurement error. So, most para-tances up to 100ft in a noisy environment. Connect thesitic thermocouple errors are swamped out.

twisted pair to DXP_ and DXN_ and the shield to GND,7)Use wide traces. Narrow ones are more inductive

and leave the shield’s remote end unterminated.

and tend to pick up radiated noise. The 10milExcess capacitance at DX_ _ limits practical remote-sen-widths and spacings recommended in Figure 2 aresor distances (see the Typical Operating Characteristics).not absolutely necessary (as they offer only a minorFor very long cable runs, the cable’s parasitic capaci-improvement in leakage and noise), but try to usetance often provides noise filtering, so the 2200pF capac-them where practical.itor can often be removed or reduced in value.

8)Copper cannot be used as an EMI shield, and only

Cable resistance also affects remote-sensor accuracy;ferrous materials such as steel work well. Placing a1Ωseries resistance introduces about +0.5°C error.

copper ground plane between the DXP_ to DXN_traces and traces carrying high-frequency noise sig-Low-Power Standby Mode

nals does not help reduce EMI.

Standby mode disables the ADC and reduces the sup-ply-current drain to less than 12µA. Enter standbyPC Board Layout Checklist

mode by forcing the STBYpin low or through the•Place the MAX1668/MAX1805/MAX19as close asRUN/STOP bit in the configuration byte register.possible to the remote diodes.

Hardware and software standby modes behave almost•Keep traces away from high voltages (+12V bus).identically: all data is retained in memory, and the SMBinterface is alive and listening for reads and writes.

•Keep traces away from fast data buses and CRTs.Activate hardware standby mode by forcing the STBY•Use recommended trace widths and spacings.pin low. In a notebook computer, this line can be con-•Place a ground plane under the traces.

nected to the system SUSTAT# suspend-state signal. •Use guard traces flanking DXP_ and DXN_ and con-The STBYpin low state overrides any software conversionnecting to GND.

command. If a hardware or software standby commandis received while a conversion is in progress, the conver-_______________________________________________________________________________________

MAX1668/MAX1805/MAX19†元器件交易网www.cecb2b.comMultichannel Remote/Local Temperature SensorsMAX1668/MAX1805/MAX19†sion cycle is truncated, and the data from that conversionis not latched into either temperature-reading register. Theprevious data is not changed and remains available.In standby mode, supply current drops to about 3µA.At very low supply voltages (under the power-on-resetthreshold), the supply current is higher due to theaddress pin bias currents. It can be as high as 100µA,depending on ADD0 and ADD1 settings.

tion. Use caution with the shorter protocols in multimastersystems, since a second master could overwrite the com-mand byte without informing the first master.

The temperature data format is 7 bits plus sign in two’s-com-plement form for each channel, with each data bit represent-ing 1°C (Table 2), transmitted MSB first. Measurements areoffset by +0.5°C to minimize internal rounding errors; forexample, +99.6°C is reported as +100°C. SMBus Digital Interface

From a software perspective, the MAX1668/MAX1805/MAX19appear as a set of byte-wide registers thatcontain temperature data, alarm threshold values, orcontrol bits. A standard SMBus 2-wire serial interface isused to read temperature data and write control bits andalarm threshold data. Each A/D channel within thedevices responds to the same SMBus slave address fornormal reads and writes.

The MAX1668/MAX1805/MAX19employ four standardSMBus protocols: write byte, read byte, send byte, andreceive byte (Figure 3). The shorter receive byte protocolallows quicker transfers, provided that the correct dataregister was previously selected by a read byte instruc-Write Byte FormatSADDRESS7 bitsSlave Address: equiva-lent to chip-select line ofa 3-wire interfaceRead Byte FormatSADDRESS7 bitsSlave Address: equiva-lent to chip-select lineSend Byte FormatSADDRESS7 bitsWRACKCOMMAND8 bitsCommand Byte: sends com-mand with no dataACKPWRACKCOMMAND8 bitsCommand Byte: selectswhich register you arereading fromACKSADDRESS7 bitsRDWRACKCOMMAND8 bitsCommand Byte: selects whichregister you are writing toACKAlarm Threshold Registers

Ten (six for MAX1805) registers store alarm thresholddata, with high-temperature (THIGH) and low-tempera-ture (TLOW) registers for each A/D channel. If eithermeasured temperature equals or exceeds the corre-sponding alarm threshold value, an ALERTinterrupt isasserted.

The power-on-reset (POR) state of all THIGHregisters ofthe MAX1668 and MAX1805 is full scale (0111 1111, or+127°C). The POR state of the channel 1 THIGHregisterof the MAX19 is 0110 1110 or +110°C, while all otherchannels are at +127°C. The POR state of all TLOWreg-isters is 1100 1001 or -55°C.

DATA8 bitsACKP1Data Byte: data goes into the registerset by the command byte (to setthresholds, configuration masks, andsampling rate)ACKDATA8 bits///PSlave Address: repeateddue to change in data-flow directionReceive Byte FormatSADDRESS7 bitsRDACKData Byte: reads fromthe register set by thecommand byteDATA8 bits///PS = Start conditionP = Stop conditionShaded = Slave transmission/// = Not acknowledgedData Byte: This command onlyworks immediately following aRead Byte. Reads data from theregister commanded by that lastRead Byte; also used for SMBusAlert Response return addressFigure 3. SMBus Protocols10

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Temperature Sensors

Table 2. Data Format (Two’s Complement)Table 3. Read Format for Alert ResponseAddress (0001100)

TEMPROUNDED(°C)TEMPDIGITAL OUTPUT DATA BITS(°C)BITNAMEFUNCTION

SIGNMSBLSB+130.00+127011111117(MSB)ADD7+127.00+127011111116ADD6+126.50+127011111115ADD5Provide the current

+126.00+12601111110MAX1668/MAX1805/MAX194ADD4slave address that was latched at+25.25+25000110013ADD3POR (Table 8)

+0.50+1000000002ADD2+0.25+0000000001ADD1+0.00+0000000000-0.25+000000000(LSB)

Logic 1

-0.50+000000000-0.75-111111111-1.00-111111111-25.00-2511100111Interrupts are generated in response to T-25.50-2511100110comparisons and when a remote diode is disconnectedHIGHand TLOW-54.75-5511001001(for continuity fault detection). The interrupt does not haltautomatic conversions; new temperature data continues-55.00-5511001001to be available over the SMBus interface after ALERTis-65.00-6510111111asserted. The interrupt output pin is open drain so that-70.00-6510111111devices can share a common interrupt line. The interruptrate can never exceed the conversion rate.

Diode Fault AlarmThe interface responds to the SMBus alert responseThere is a continuity fault detector at DXP_ that detectsaddress, an interrupt pointer return-address featurewhether the remote diode has an open-circuit condi-(see Alert Response Addresssection). Prior to takingtion. At the beginning of each conversion, the diodecorrective action, always check to ensure that an inter-fault is checked, and the status byte is updated. Thisrupt is valid by reading the current temperature.

fault detector is a simple voltage detector; if DXP_ risesabove VCC- 1V (typ) due to the diode current source, aAlert Response Address

fault is detected. Note that the diode fault is notThe SMBus alert response interrupt pointer provideschecked until a conversion is initiated, so immediatelyquick fault identification for simple slave devices thatafter power-on reset, the status byte indicates no faultlack the complex, expensive logic needed to be a busis present, even if the diode path is broken.

master. Upon receiving an ALERTinterrupt signal, theIf any remote channel is shorted (DXP_ to DXN_ orhost master can broadcast a receive byte transmissionDXP_ to GND), the ADC reads 0000 0000 so as not toto the alert response slave address (0001 100). Thentrip either the Tany slave device that generated an interrupt attemptstings. In applications that are never subjected to 0°C inHIGHor TLOWalarms at their POR set-to identify itself by putting its own address on the busnormal operation, a 0000 0000 result can be checked(Table 3).

to indicate a fault condition in which DXP_ is acciden-The alert response can activate several different slavetally short circuited. Similarly, if DXP_ is short circuiteddevices simultaneously, similar to the I2C general call. Ifto Vmore than one slave attempts to respond, bus arbitra-channels, and the device alarms.

CC, the ADC reads +127°C for all remote and localtion rules apply, and the device with the lower addressALERTInterrupts

code wins. The losing device does not generate anacknowledge and continues to hold the ALERTline lowThe ALERTinterrupt output signal is latched and canuntil serviced (implies that the host interrupt input is

only be cleared by reading the alert response address.

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MAX1668/MAX1805/MAX19†元器件交易网www.cecb2b.comMultichannel Remote/Local Temperature SensorsMAX1668/MAX1805/MAX19†level sensitive). Successful reading of the alertresponse address clears the interrupt latch.

Command Byte Functions

The 8-bit command byte register (Table 4) is the masterindex that points to the various other registers within theMAX1668/MAX1805/MAX19. The register’s POR

state is 0000 0000, so that a receive byte transmission(a protocol that lacks the command byte) that occursimmediately after POR returns the current local temper-ature data.

Table 4. Command Byte Bit Assignments for MAX1668/MAX1805/MAX19REGISTERRITRET1RET2RET3**RET4**RS1RS2RCRIHLRILLREHL1RELL1REHL2RELL2REHL3**RELL3**REHL4**RELL4**WCWIHLWILLWEHI1WELL1WEHI2WELL2WEHI3**WELL3**WEHI4**WELL4**MFG IDDEV IDCOMMAND00h01h02h03h04h05h06h07h08h09h0Ah0Bh0Ch0Dh0Eh0Fh10h11h12h13h14h15h16h17h18h19h1Ah1Bh1ChFEhFFhPOR STATE 0000 0000* 0000 0000* 0000 0000* 0000 0000* 0000 0000*0000 00000000 00000000 00000111 11111100 10010111 1111(0110 1110)1100 10010111 11111100 10010111 11111100 10010111 11111100 1001N/AN/AN/AN/AN/AN/AN/AN/AN/AN/AN/A0100 11010000 0011 (0000 0101)[0000 1011]FUNCTIONRead local temperatureRead remote DX1 temperatureRead remote DX2 temperatureRead remote DX3 temperatureRead remote DX4 temperatureRead status byte 1Read status byte 2Read Configuration ByteRead local THIGH limitRead local TLOW limitRead remote DX1 THIGH limit (MAX19)Read remote DX1 TLOW limitRead remote DX2 THIGH limitRead remote DX2 TLOW limitRead remote DX3 THIGH limitRead remote DX3 TLOW limitRead remote DX4 THIGH limitRead remote DX4 TLOW limitWrite configuration byteWrite local THIGH limitWrite local TLOW limitWrite remote DX1 THIGH limitWrite remote DX1 TLOW limitWrite remote DX2 THIGH limitWrite remote DX2 TLOW limitWrite remote DX3 THIGH limitWrite remote DX3 TLOW limitWrite remote DX4 THIGH limitWrite remote DX4 TLOW limitRead manufacture IDRead device ID (for MAX1805) [for MAX19]*If the device is in hardware standby mode at POR, all temperature registers read 0°C.**Not available for MAX1805.12

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元器件交易网www.cecb2b.comMultichannel Remote/Local

Temperature Sensors

Manufacturer and Deviceon the status bits to indicate reversals in long-term tem-ID Codes

perature changes and instead use a current tempera-Two ROM registers provide manufacturer and deviceture reading to establish the trend direction.

ID codes. Reading the manufacturer ID returns 4Dh,Conversion Rate

which is the ASCII code M (for Maxim). Reading theThe MAX1668/MAX1805/MAX19 are continuouslydevice ID returns 03h for MAX1668, 05h for MAX1805,measuring temperature on each channel. The typicaland 0Bh for MAX19. If the read word 16-bit SMBusconversion rate is approximately three conversions/sprotocol is employed (rather than the 8-bit Read Byte),(for both devices). The resulting data is stored in thethe least significant byte contains the data and the mosttemperature data registers.

significant byte contains 00h in both cases.

Slave Addresses

Configuration Byte Functions

The MAX1668/MAX1805/MAX19 appear to theThe configuration byte register (Table 5) is used toSMBus as one device having a common address for allmask (disable) interrupts and to put the device in soft-ADC channels. The device address can be set to oneware standby mode.

of nine different values by pin-strapping ADD0 andStatus Byte Functions

ADD1 so that more than one MAX1668/MAX1805/The two status byte registers (Tables 6 and 7) indicateMAX19 can reside on the same bus without addresswhich (if any) temperature thresholds have beenconflicts (Table 8).

exceeded. The first byte also indicates whether theThe address pin states are checked at POR only, andADC is converting and whether there is an open circuitthe address data stays latched to reduce quiescentin a remote-diode DXP_ to DXN_ path. After POR, thesupply current due to the bias current needed for high-Znormal state of all the flag bits is zero, assuming nonestate detection.

of the alarm conditions are present. The status byte isThe MAX1668/MAX1805/MAX19 also respond to thecleared by any successful read of the status byte,SMBus alert response slave address (see the Alertunless the fault persists. Note that the ALERTinterruptResponse Addresssection).

latch is not automatically cleared when the status flagbit is cleared.

POR and Undervoltage Lockout

When reading the status byte, you must check for inter-The MAX1668/MAX1805/MAX19 have a volatilenal bus collisions caused by asynchronous ADC timing,memory. To prevent ambiguous power-supply condi-or else disable the ADC prior to reading the status bytetions from corrupting the data in memory and causing(through the RUN/STOP bit in the configuration byte).erratic behavior, a POR voltage detector monitors Vand clears the memory if VCCTo check for internal bus collisions, read the statusthe Electrical CharacteristicsCCfalls below 1.8V (typ, seetable). When power is firstbyte. If the least significant 7 bits are ones, discard theapplied and Vdata and read the status byte again. The status bitsblocks begin operating, although reads and writes atCCrises above 1.85V (typ), the logicLHIGH, LLOW, RHIGH, and RLOW are refreshed on theVSMBus clock edge immediately following the stop con-VCClevels below 3V are not recommended. A secondCCcomparator, the ADC UVLO comparator, preventsdition, so there is no danger of losing temperature-relat-the ADC from converting until there is sufficient head-ed status data as a result of an internal bus collision.room (VCC= 2.8V typ).

The OPEN status bit (diode continuity fault) is onlyrefreshed at the beginning of a conversion, so OPENPower-Up Defaults

data is lost. The ALERTinterrupt latch is independent of•Interrupt latch is cleared.

the status byte register, so no false alerts are generated•Address select pins are sampled.

by an internal bus collision.

•ADC begins converting.

If the THIGH and TLOW limits are close together, it’spossible for both high-temp and low-temp status bits to•Command byte is set to 00h to facilitate quickbe set, depending on the amount of time between sta-remote receive byte queries.

tus read operations (especially when converting at the•THIGHand TLOWregisters are set to max and minfastest rate). In these circumstances, it’s best not to rely

limits, respectively.

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MAX1668/MAX1805/MAX19†元器件交易网www.cecb2b.comMultichannel Remote/Local Temperature SensorsMAX1668/MAX1805/MAX19†Table 5. Configuration Byte Bit Assignments

BIT7 (MSB)6543201NAMEMASKALLRUN/STOPMASK4*MASK3*MASK2MASK1IBIAS1IBIAS0POR00000000FUNCTIONMasks all ALERT interrupts when high.Standby mode control bit. If high, the device immediately stops converting andenters standby mode. If low, the device converts.Masks remote DX4 interrupts when high.Masks remote DX3 interrupts when high.Masks remote DX2 interrupts when high.Masks remote DX1 interrupts when high.M ed i um /l ow -b ia s contr ol b i t. H ig h = l ow b ia s, l ow = m ed iu m b ia s. IBIAS 0 m ust b e l ow .High-bias control bit. High bias on DXP_ when high. Overrides IBIAS1.*Not available for MAX1805.Table 6. Status Byte Bit 1 AssignmentsBIT7 (MSB)6543210NAMEBUSYLHIGH†LLOW†OPEN†ALARM†N/AN/AN/AFUNCTIONA high indicates that the ADC is busy converting.A high indicates that the local high-temperature alarm has activated.A high indicates that the local low-temperature alarm has activated.A high indicates one of the remote-diode continuity (open-circuit) faults.A high indicates one of the remote-diode channels has over/undertemperature alarm.N/AN/AN/A†These flags stay high until cleared by POR, or until the status byte register is read.Table 7. Status Byte 2 Bit AssignmentsBIT7 (MSB)6543210NAMERLOW1RHIGH1RLOW2RHIGH2RLOW3*RHIGH3*RLOW4*RHIGH4*FUNCTIONA high indicates that the DX1 low-temperature alarm has activated.A high indicates that the DX1 high-temperature alarm has activated.A high indicates that the DX2 low-temperature alarm has activated.A high indicates that the DX2 high-temperature alarm has activated.A high indicates that the DX3 low-temperature alarm has activated.A high indicates that the DX3 high-temperature alarm has activated.A high indicates that the DX4 low-temperature alarm has activated.A high indicates that the DX4 high-temperature alarm has activated.Note:All flags in this byte stay high until cleared by POR or until the status byte is read.*Not available for MAX1805.

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Temperature Sensors

AtBDEFGHIJKLOWtCHIGHSMBCLKSMBDATAtSU:STAtHD:STAtSU:DATtSU:STOtBUFA = START CONDITIONE = SLAVE PULLS SMBDATA LINE LOWI = ACKNOWLEDGE CLOCK PULSEB = MSB OF ADDRESS CLOCKED INTO SLAVEF = ACKNOWLEDGE BIT CLOCKED INTO MASTERJ = STOP CONDITIONC = LSB OF ADDRESS CLOCKED INTO SLAVEG = MSB OF DATA CLOCKED INTO MASTERK = NEW START CONDITIOND = R/W BIT CLOCKED INTO SLAVEH = LSB OF DATA CLOCKED INTO MASTERFigure 4. SMBus Read Timing Diagram

AtBCDEFGHIJKLMLOWtHIGHSMBCLKSMBDATAtSU:STAtHD:STAtSU:DATtHD:DATtSU:STOtBUFA = START CONDITIONF = ACKNOWLEDGE BIT CLOCKED INTO MASTERJ = ACKNOWLEDGE CLOCKED INTO MASTERB = MSB OF ADDRESS CLOCKED INTO SLAVEG = MSB OF DATA CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSEC = LSB OF ADDRESS CLOCKED INTO SLAVEH = LSB OF DATA CLOCKED INTO SLAVEL = STOP CONDITION, DATA EXECUTED BY SLAVED = R/W BIT CLOCKED INTO SLAVEI = SLAVE PULLS SMBDATA LINE LOWM = NEW START CONDITION E = SLAVE PULLS SMBDATA LINE LOW Figure 5. SMBus Write Timing Diagram

Table 8. Slave Address Decoding (ADD0and ADD1)ADD0ADD1ADDRESSGNDGND0011 000GNDHigh-Z0011 001GNDVCC0011 010High-ZGND0101 001High-ZHigh-Z0101 010High-ZVCC0101 011VCCGND1001 100VCCHigh-Z1001 101VCCVCC1001 110Note:High-Z means that the pin is left unconnected and floating.

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MAX1668/MAX1805/MAX19†元器件交易网www.cecb2b.comMultichannel Remote/Local Temperature SensorsMAX1668/MAX1805/MAX19†Package 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.)

QSOP.EPS16______________________________________________________________________________________

元器件交易网www.cecb2b.comMultichannel Remote/Local

Temperature Sensors

Package 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.mm04.4POSSTMaxim 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.

Printed USA

is a registered trademark of Maxim Integrated Products.

MAX1668/MAX1805/MAX19†

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