General Description
The MAX31820 ambient temperature sensor provides
9-bit to 12-bit Celsius temperature measurements with
±0.5°C accuracy over a +10°C to +45°C temperature
range. Over its entire -55°C to +125°C operating range,
the device has ±2.0°C accuracy.
The device communicates over a 1-Wire® bus that, by
definition, requires only one data line (and ground) for
communication with a central microprocessor. In addition,
the device can derive power directly from the data line
(“parasite power”), eliminating the need for an external
power supply. Requiring so few pins enables the device
to be placed in a 3-pin TO-92 package. The form factor
of this package allows the device to be placed above
the board and thus measure the ambient temperature of
a system, as opposed to the board temperature that a
surface-mount package would measure.
Each MAX31820 has a unique 64-bit serial code, which
allows multiple MAX31820 devices to function on the same
1-Wire bus. Therefore, it is simple to use one microproces-
sor to control many devices distributed over a large area.
Applications
● HVACEnvironmentalControls
● TemperatureMonitoringSystemsInsideBuildings,
Equipment, or Machinery
● ProcessMonitoringandControlSystems
● ThermostaticControls
● IndustrialSystems
● ConsumerProducts
● Thermometers
● AnyThermallySensitiveSystem
Benets and Features
● Unique1-WireInterfaceRequiresOnlyOnePortPin
for Communication
● EachDevicehasaUnique64-BitSerialCodeStored
inOn-BoardROM
● MultidropCapabilitySimplifiesDistributed
Temperature-SensingApplications
● RequiresNoExternalComponents
● CanBePoweredfromDataLine;3.0Vto3.7V
Power-SupplyRange
● MeasuresTemperaturesfrom-55°Cto+125°C(-67°F
to+257°F)
● ±0.5°CAccuracyfrom+10°Cto+45°C
● ThermometerResolutionisUser-Selectablefrom
9Bitsto12Bits
● ConvertsTemperatureto12-BitDigitalWordin
750ms(Max)
● User-DefinableNonvolatile(NV)AlarmSettings
● AlarmSearchCommandIdentifiesandAddresses
DevicesWhoseTemperatureisOutsideProgrammed
Limits(TemperatureAlarmCondition)
● Availablein3-PinTO-92Package
● TO-92PackageAllowsMeasurementofAmbient
Temperature
● SoftwareCompatiblewiththeDS1822andDS18B20
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part, refer
to www.maximintegrated.com/MAX31820.related.
1-Wire is a registered trademark of Maxim Integrated Products, Inc.
MAX31820
64-BIT ROM
AND
1-Wire PORT
PARASITE-
POWER
CIRCUIT
CPP
VPU
4.7kΩ
DQ
GND
VDD
MEMORY
CONTROL LOGIC
SCRATCHPAD
8-BIT CRC GENERATOR
CONFIGURATION REGISTER (EEPROM)
TEMPERATURE REGISTER
ALARM HIGH TRIGGER
(TH) REGISTER (EEPROM)
ALARM LOW TRIGGER
(TL) REGISTER (EEPROM)
POWER-
SUPPLY
SENSE
MAX31820 1-Wire Ambient Temperature Sensor
19-6731; Rev 0; 6/13
Block Diagram
VoltageRangeonAnyPinRelativetoGround ....-0.5Vto+6.0V
Operating Temperature Range ......................... -55°C to +125°C
StorageTemperatureRange ............................ -55°C to +125°C
SolderingTemperature(reflow) ....................................... +260°C
(VDD=3.0Vto3.7V,TA=-55°Cto+125°C,unlessotherwisenoted.)(Note1)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SupplyVoltage VDD Localpower(Note2) +3.0 +3.7 V
PullupSupplyVoltage
(Notes2,3) VPU Parasitepower +3.0 +3.7 V
Localpower +3.0 VDD
ThermometerError(Note4) TERR
+10°C to +45°C ±0.5 °C
-55°C to +125°C ±2
InputLogic-Low VIL (Notes2,5,6) -0.3 +0.8 V
InputLogic-High(Notes2,7) VIH
Localpower +2.2
lower
of3.7
or
(VDD +
0.3) V
Parasitepower +3.0
lower
of3.7
or
(VDD +
0.3)
SinkCurrent ILVI/O=0.4V(Note2) 4.0 mA
StandbyCurrent IDDS (Notes8,9) 750 1000 nA
Active Current IDD VDD=5V(Note10) 1 1.5 mA
DQInputCurrent IDQ (Note11) 5 µA
Drift (Note12) ±0.2 °C
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
2
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
DC Electrical Characteristics
(VDD=3.0Vto3.7V,TA=-55°Cto+125°C,unlessotherwisenoted.)(Note1)
Note 1: Limitsare100%testedatTA = +25°C and TA=+85°C.Limitsovertheoperatingtemperaturerangeandrelevantsupply
voltage are guaranteed by design and characterization.
Note 2: All voltages are referenced to ground.
Note 3: The pullup supply voltage specification assumes that the pullup device is ideal, and therefore the high level of the pullup
isequaltoVPU.Inordertomeetthedevice’sVIH spec, the actual supply rail for the strong pullup transistor must include
marginforthevoltagedropacrossthetransistorwhenitisturnedon;thus:VPU_ACTUAL=VPU_IDEAL+VTRANSISTOR.
Note 4: Seetypicalperformancecurve.
Note 5: Logic-lowvoltagesarespecifiedatasinkcurrentof4mA.
Note 6: Toguaranteeapresencepulseunderlow-voltageparasite-powerconditions,VILMAX may have to be reduced to as low as
0.5V.
Note 7: Logic-highvoltagesarespecifiedatasourcecurrentof1mA.
Note 8: Standbycurrentspecifiedupto+70°C.Standbycurrenttypicallyis3µAat+125°C.
Note 9: To minimize IDDS,DQshouldbewithinthefollowingranges:VGND≤VDQ≤VGND+0.3VorVDD-0.3V≤VDQ≤VDD.
Note 10: ActivecurrentreferstosupplycurrentduringactivetemperatureconversionsorEEPROMwrites.
Note 11: DQlineishigh(high-Zstate).
Note 12: Driftdataisbasedona1000-hourstresstestat+125°C.
Note 13: Seethe1-Wire Timing Diagrams.
Note 14: Underparasitepower,iftRSTL > 960µs, a power-on reset may occur.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Temperature Conversion Time tCONV
9-bit resolution 93.75
ms
10-bit resolution 187.5
11-bit resolution 375
12-bit resolution 750
TimetoStrongPullupOn tSPON StartConvertTcommand 10 µs
TimeSlot tSLOT (Note13) 60 120 µs
Recovery Time tREC (Note13) 1 µs
Write-ZeroLowTime tLOW0 (Note13) 60 120 µs
Write-OneLowTime tLOW1 (Note13) 1 15 µs
ReadDataValid tRDV (Note13) 15 µs
ResetTimeHigh tRSTH (Note13) 480 µs
ResetTimeLow tRSTL (Notes13,14) 480 µs
Presence-DetectHigh tPDHIGH (Note13) 15 60 µs
Presence-DetectLow tPDLOW (Note13) 60 240 µs
Capacitance CIN/OUT 25 pF
NONVOLATILE MEMORY (TA = -55°C to +100°C)
NonvolatileWriteCycleTime tWR 2 10 ms
EEPROMWrites NEEWR -55°C to +55°C 50k Writes
EEPROMDataRetention tEEDR -55°C to +55°C 10 Years
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
3
AC Electrical Characteristics
1-Wire WRITE-ZERO TIME SLOT
1-Wire READ-ZERO TIME SLOT
1-Wire RESET PULSE
1-Wire PRESENCE DETECT
RESET PULSE FROM HOST
PRESENCE DETECT
tSLOT
tSLOT
tRSTL tRSTH
START OF NEXT CYCLE
START OF NEXT CYCLE
tLOW0
tREC
tREC
tPDHIGH
tPDLOW
tRDV
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
4
1-Wire Timing Diagrams
Detailed Description
The MAX31820 ambient temperature sensor provides
9-bit to 12-bit Celsius temperature measurements with
±0.5°C accuracy over a +10°C to +45°C temperature
range. Over its entire -55°C to +125°C operating range,
the device has ±2.0°C accuracy. The device commu-
nicates over a 1-Wire bus that, by definition, requires
only one data line (and ground) for communication with
a central microprocessor. In addition, the device can
derive power directly from the data line (“parasite power”),
eliminating the need for an external power supply.
Requiring so few pins enables the device to be placed
in a 3-pin TO-92 package. The form factor of this pack-
age allows the device to be placed above the board and
thus measure the ambient temperature of a system, as
opposed to the board temperature that a surface-mount
package would measure.
Each device has a unique 64-bit serial code, allowing
multiple MAX31820 devices to function on the same
1-Wire bus. Therefore, it is simple to use one micro-
processor to control many devices distributed over a
large area. The 64-bit ROM stores the device’s unique
serial code. The scratchpad memory contains the 2-byte
temperature register that stores the digital output from
the temperature sensor. In addition, the scratchpad pro-
vides access to the 1-byte upper and lower alarm trigger
registers (TH and TL) and the 1-byte configuration regis-
ter. The configuration register allows the user to set the
resolution of the temperature-to-digital conversion to 9, 10,
11, or 12 bits. The TH, TL, and configuration registers are
nonvolatile (EEPROM), so they retain data when the
device is powered down.
The device uses Maxim Integrated’s exclusive 1-Wire
bus protocol that implements bus communication using
one control signal. The control line requires a weak pullup
resistor since all devices are linked to the bus through a
three-stateoropen-drainport(i.e.,theMAX31820’sDQ
pin). In this bus system, the microprocessor (the master
device) identifies and addresses devices on the bus
using each device’s unique 64-bit code. Because each
device has a unique code, the number of devices that
can be addressed on one bus is virtually unlimited. The
1-Wire bus protocol, including detailed explanations of the
commands and time slots, is covered in the 1-Wire Bus
System section.
The device can also operate without an external power
supply. Power is instead supplied through the 1-Wire
pullupresistorthroughtheDQpinwhenthebusishigh.
The high bus signal also charges an internal capacitor
(CPP), which then supplies power to the device when the
bus is low. This method of deriving power from the 1-Wire
bus is referred to as “parasite power.” Alternatively, an
externalsupplyonVDD can also power the device.
Operation
Measuring Ambient Temperature
A conventional surface-mount temperature sensor IC has
an excellent thermal connection to the circuit board on
whichitismounted.Heattravelsfromtheboardthrough
the leads to the sensor die. Air temperature can affect
2
3
1
3
2
1
VDD
DQ
GND
TO-92
FRONT VIEW
MAX31820
SIDE VIEW
PIN NAME FUNCTION
1GND Ground
2DQ DataIn/Out
3VDD OptionalPowerSupply
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
5
Pin Description
Pin Conguration
*The power-on-reset value of the temperature register is +85°C.
the die temperature, but the sensor’s package does not
conduct heat as well as the leads, so board temperature
has the greatest influence on the measured temperature.
The device’s TO-92 package allows the sensor die to be
positioned above the board. The leads still conduct some
heat from the board, but because there is significant lead
area in contact with air, their temperature is also strongly
affectedbyairtemperature.Followtheguidelinesbelowto
getthebestresultswhenmeasuringambienttemperature:
• If air is moving (e.g., due to cooling fans), place the
sensor in the path of the air stream. This causes the
ambient temperature to influence the sensor tempera-
ture more strongly.
• If the board contains components that will heat it,
mount the sensor as far as possible from those com-
ponents. This makes the temperature in the vicinity of
the sensor closer to the temperature of the ambient air.
• PCB traces and ground planes conduct heat from
other components to the sensor. As much as practical,
avoid copper in the vicinity of the sensor.
The device’s core functionality is its direct-to-digital tem-
perature sensor. The resolution of the temperature sensor
is user-configurable to 9, 10, 11, or 12 bits, corresponding
to increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C,
respectively. The default resolution at power-up is 12
bits. The device powers up in a low-power idle state. To
initiate a temperature measurement andA-to-D conver-
sion, the master must issue a Convert T [44h] command.
Following the conversion, the resulting thermal data is
stored in the 2-byte temperature register in the scratch-
pad memory and the device returns to its idle state. If the
device is powered by an external supply, the master can
issue read time slots (see the 1-Wire Bus System section)
after the Convert T command, and the device responds
by transmitting 0 while the temperature conversion is in
progress and 1 when the conversion is done. If the device
is powered with parasite power, this notification technique
cannot be used since the bus must be pulled high by a
strong pullup during the entire temperature conversion.
The bus requirements for parasite power are explained in
detail in the Powering the MAX31820 section.
The output temperature data is calibrated in degrees
Celsius; for Fahrenheit applications, a lookup table or
conversion routine must be used. The temperature data
is stored as a 16-bit sign-extended two’s complement
number in the temperature register (see the Temperature
Register Format).Thesignbits(S)indicateifthetempera-
tureispositiveornegative:forpositivenumbersS=0and
fornegativenumbersS=1.Ifthedeviceisconfigured
for 12-bit resolution, all bits in the temperature register
containvaliddata.For11-bitresolution,bit0isundefined.
For10-bitresolution,bits1and0areundefined,andfor
9-bit resolution bits 2, 1, and 0 are undefined. Table 1
gives examples of digital output data and the correspond-
ing temperature reading for 12-bit resolution conversions.
Temperature Register Format
Table 1. Temperature/Data Relationship
BIT 15 BIT 14 BIT 13 BIT 12 BIT 11 BIT 10 BIT 9 BIT 8
MSB SSSSS262524
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
LSB 232221202-1 2-2 2-3 2-4
TEMPERATURE (°C) DIGITAL OUTPUT (BINARY) DIGITAL OUTPUT (HEX)
+125 0000 0111 1101 0000 07D0h
+85* 0000 0101 0101 0000 0550h
+25.0625 0000 0001 1001 0001 0191h
+10.125 0000 0000 1010 0010 00A2h
+0.5 0000 0000 0000 1000 0008h
00000 0000 0000 0000 0000h
-0.5 1111 1111 1111 1000 FFF8h
-10.125 1111 1111 0101 1110 FF5Eh
-25.0625 1111 1110 0110 1111 FE6Fh
-55 1111 1100 1001 0000 FC90h
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
6
Alarm Signaling
After the device performs a temperature conversion, the
temperature value is compared to the user-defined two’s
complement alarm trigger values stored in the 1-byte TH
and TL registers (see TH and TL Register Format). The
signbit(S) indicatesifthe valueispositiveornegative;
forpositivenumbersS=0andfornegativenumbersS
= 1. The TH and TLregistersarenonvolatile(EEPROM)
so they retain data when the device is powered down.
TH and TL can be accessed through bytes 2 and 3 of the
scratchpad, as explained in the Memory section.
Onlybits11:4ofthetemperatureregisterareusedinthe
TH and TL comparison since TH and TLare 8-bit registers.
If the measured temperature is lower than or equal to TL
or higher than or equal to TH, an alarm condition exists
and an alarm flag is set inside the device. This flag is
updatedaftereverytemperaturemeasurement;therefore,
if the alarm condition goes away, the flag is turned off after
the next temperature conversion.
The master device can check the alarm flag status of
all MAX31820 devices on the bus by issuing an Alarm
Search[ECh]command.Anydeviceswithasetalarmflag
respond to the command, so the master can determine
exactly which devices have experienced an alarm condi-
tion. If an alarm condition exists and the TH or TL settings
have changed, another temperature conversion should be
done to validate the alarm condition.
TH and TL Register Format
Powering the MAX31820
The device can be powered by an external supply on
theVDD pin, or it can operate in “parasite power” mode,
which allows the device to function without a local exter-
nalsupply.Parasitepowerisveryusefulforapplications
that require remote temperature sensing, or those that
are very space constrained. Figure1 shows the device’s
parasite-power control circuitry, which “steals” power
fromthe1-WirebusthroughtheDQpinwhenthebusis
high. The stolen charge powers the device while the bus
is high, and some of the charge is stored on the parasite-
power capacitor (CPP) to provide power when the bus is
low. When the device is used in parasite-power mode,
theVDD pin must be connected to ground.
In parasite-power mode, the 1-Wire bus and CPP can
provide sufficient current to the device for most opera-
tions as long as the specified timing and voltage require-
ments are met (see the DC Electrical Characteristics and
AC Electrical Characteristics tables).However,whenthe
device is performing temperature conversions or copy-
ingdatafromthescratchpadmemorytoEEPROM,the
operating current can be as high as 1.5mA. This current
can cause an unacceptable voltage drop across the weak
1-Wire pullup resistor and is more current than can be
supplied by CPP. To ensure that the device has sufficient
supply current, it is necessary to provide a strong pullup
on the 1-Wire bus whenever temperature conversions
Figure 1. Supplying the Parasite-Powered MAX31820 During Temperature Conversions
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
S26252423222120
µP
VPU
4.7kΩ
VPU
1-Wire BUS TO OTHER 1-Wire DEVICES
MAX31820
GND DQ VDD
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
7
are taking place, or data is being copied from the scratch-
padtoEEPROM.Thiscanbeaccomplishedbyusinga
MOSFETtopullthebusdirectlytotherail,asshownin
Figure1. The 1-Wire bus must be switched to the strong
pullup within 10µs (max) after a Convert T [44h] or Copy
Scratchpad[48h]commandisissued,andthebusmust
be held high by the pullup for the duration of the conver-
sion (tCONV) or data transfer (tWR = 10ms). No other
activity can take place on the 1-Wire bus while the pullup
is enabled.
The device can also be powered by the conventional
method of connecting an external power supply to the
VDD pin, as shown in Figure 2. The advantage of this
methodis thattheMOSFETpullupis notrequired,and
the 1-Wire bus is free to carry other traffic during the
temperature-conversion time.
The use of parasite power is not recommended for
temperatures above +100°C since the device may not be
able to sustain communications due to the higher leakage
currentsthatcanexistatthesetemperatures.Forapplica-
tions in which such temperatures are likely, it is strongly
recommended that the device be powered by an external
power supply.
In some situations the bus master might not know whether
the devices on the bus are parasite powered or powered
by external supplies. The master needs this information
to determine if the strong bus pullup should be used
during temperature conversions. To get this informa-
tion,themastercanissueaSkipROM[CCh]command
followed by a Read Power Supply [B4h] command,
followed by a read time slot. During the read time slot,
parasite-powered devices pull the bus low, and exter-
nally powered devices let the bus remain high. If the
bus is pulled low, the master knows that it must supply
the strong pullup on the 1-Wire bus during temperature
conversions.
64-Bit Lasered ROM Code
Each device contains a unique 64-bit code stored in ROM
(Figure3). The least significant 8 bits of the ROM code
contain the device’s 1-Wire family code, 28h. The next
48 bits contain a unique serial number. The most sig-
nificant 8 bits contain a cyclic-redundancy-check (CRC)
byte that is calculated from the first 56 bits of the ROM
code. A detailed explanation of the CRC bits is provided
in the CRC Generation section. The 64-bit ROM code and
associated ROM function control logic allow the device to
operate as a 1-Wire device using the protocol detailed in
the 1-Wire Bus System section.
Figure 2. Powering the MAX31820 with an External Supply
Figure 3.64-Bit Lasered ROM Code
µP
VPU
4.7kΩ
1-Wire BUS TO OTHER 1-Wire DEVICES
(EXTERNAL SUPPLY)VDD
MAX31820
GND DQ VDD
MSb
8-BIT
CRC CODE 48-BIT SERIAL NUMBER
MSb MSbLSb
LSb
LSb
8-BIT FAMILY CODE
(28h)
MSbLSb
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
8
Memory
The device’s memory is organized as shown in Figure4.
The memory consists of an SRAM scratchpad with non-
volatileEEPROMstorageforthehighandlowalarmtrig-
ger registers (TH and TL)andconfigurationregister.Note
that if the device alarm function is not used, the TH and TL
registers can serve as general-purpose memory. All mem-
ory commands are described in detail in the MAX31820
Function Commands section.
Byte0andbyte1ofthescratchpadcontaintheLSBand
theMSBofthetemperatureregister, respectively.These
bytesareread-only.Bytes2and3provideaccesstoTH
and TLregisters.Byte4containstheconfigurationregis-
ter data, which is explained in detail in the Configuration
Registersection.Bytes7:5arereservedforinternaluseby
thedeviceandcannotbeoverwritten.Byte8ofthescratch-
padisread-onlyandcontainstheCRCcodeforbytes7:0
of the scratchpad. The device generates this CRC using
the method described in the CRC Generation section.
Datais writtento bytes4:2ofthescratchpad usingthe
Write Scratchpad [4Eh] command; the data must be
transmitted to the device starting with the least significant
bit of byte 2. To verify data integrity, the scratchpad can
be read (using the Read Scratchpad [BEh] command)
after the data is written. When reading the scratchpad,
data is transferred over the 1-Wire bus starting with the
least significant bit of byte 0. To transfer the TH, TL, and
configurationdatafromthescratchpadtoEEPROM,the
mastermustissuetheCopyScratchpad[48h]command.
Data in the EEPROM registers is retained when the
deviceispowereddown;atpower-uptheEEPROMdata
is reloaded into the corresponding scratchpad locations.
DatacanalsobereloadedfromEEPROMtothescratch-
pad at any time using the Recall E2[B8h]command.The
master can issue read time slots following the Recall
E2 command, and the device indicates the status of the
recall by transmitting 0 while the recall is in progress and
1 when the recall is done.
Conguration Register
Byte4ofthescratchpadmemorycontainstheconfigura-
tion register, which is organized as shown in Configuration
Register Format. The user can set the conversion resolu-
tion of the device using the R0 and R1 bits in this register,
as shown in Table 2. The power-up default of these bits is
R0=1andR1=1(12-bitresolution).Notethatthereis
a direct trade-off between resolution and conversion time.
Bit7andbits4:0intheconfigurationregisterarereserved
for internal use by the device and cannot be overwritten.
Conguration Register Format
Figure 4. Memory Map
TEMPERATURE REGISTER LSB (50h)BYTE 0
TEMPERATURE REGISTER MSB (05h)BYTE 1
TH REGISTER OR USER BYTE 1*BYTE 2
TL REGISTER OR USER BYTE 2*BYTE 3
CONFIGURATION REGISTER*BYTE 4
RESERVED (FFh)BYTE 5
RESERVEDBYTE 6
RESERVED (10h)BYTE 7
CRC*BYTE 8
*POWER-UP STATE DEPENDS ON VALUE(S) STORED IN EEPROM.
SCRATCHPAD (POWER-UP STATE
SHOWN IN PARENTHESES)
EEPROM
TH REGISTER OR USER BYTE 1
TL REGISTER OR USER BYTE 2
CONFIGURATION REGISTER
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
0 R1 R0 1 1 1 1 1
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
9
CRC Generation
CRC bytes are provided as part of the device’s 64-bit
ROM code and in the 9th byte of the scratchpad memory.
The ROM code CRC is calculated from the first 56 bits
of the ROM code and is contained in the most significant
byte of the ROM. The scratchpad CRC is calculated
from the data stored in the scratchpad, and therefore
changes when the data in the scratchpad changes. The
CRCs provide the bus master with a method of data vali-
dation when data is read from the device. To verify that
data has been read correctly, the bus master must recal-
culate the CRC from the received data and then compare
this value to either the ROM code CRC (for ROM reads)
or to the scratchpad CRC (for scratchpad reads). If the
calculated CRC matches the read CRC, the data has
been received error free. The comparison of CRC values
and the decision to continue with an operation are deter-
mined entirely by the bus master. There is no circuitry
inside the device that prevents a command sequence
from proceeding if the device CRC (ROM or scratchpad)
does not match the value generated by the bus master.
The equivalent polynomial function of the CRC (ROM or
scratchpad)is:
CRC = X8 + X5 + X4 + 1
The bus master can recalculate the CRC and compare it
to the CRC values from the device using the polynomial
generator shown in Figure 5. This circuit consists of a
shift register and XOR gates, and the shift register bits
areinitializedto0.Startingwiththeleastsignificantbitof
the ROM code or the least significant bit of byte 0 in the
scratchpad, one bit at a time should be shifted into the
shift register. After shifting in the 56th bit from the ROM
orthemostsignificantbitofbyte7fromthescratchpad,
the polynomial generator contains the recalculated CRC.
Next, the 8-bit ROM code or scratchpad CRC from the
device must be shifted into the circuit. At this point, if
the recalculated CRC was correct, the shift register
contains all 0s. Additional information about the Maxim
Integrated 1-Wire CRC is available in Application Note27:
Understanding and Using Cyclic Redundancy Checks
with Maxim iButton® Products.
iButton is a registered trademark of Maxim Integrated
Products, Inc.
Table 2. Thermometer Resolution Configuration
Figure 5. CRC Generator
R1 R0 RESOLUTION (BITS) MAX CONVERSION TIME
0 0 9 93.75ms (tCONV/8)
0 1 10 187.5ms (tCONV/4)
1 0 11 375ms (tCONV/2)
1 1 12 750ms (tCONV)
1ST
STAGE
2ND
STAGE
3RD
STAGE
4TH
STAGE
7TH
STAGE
8TH
STAGE
6TH
STAGE
5TH
STAGE
X0X1X2X3X4
POLYNOMIAL = X8 + X5 + X4 + 1
INPUT DATA
X5X6X7X8
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
10
1-Wire Bus System
The 1-Wire bus system uses a single bus master to con-
trol one or more slave devices. The MAX31820 is always
a slave. When there is only one slave on the bus, the
systemisreferredtoasasingle-dropsystem;thesystem
is multidrop if there are multiple slaves on the bus. All data
and commands are transmitted least significant bit first
over the 1-Wire bus.
The following discussion of the 1-Wire bus system is
broken down into three topics: hardware configuration,
transaction sequence, and 1-Wire signaling (signal types
and timing).
Hardware Conguration
The 1-Wire bus has, by definition, only a single data line.
Each device (master or slave) interfaces to the data line
through an open-drain or three-state port. This allows
each device to release the data line when the device is
not transmitting data so the bus is available for use by
another device. The 1-Wire port of the MAX31820 (the
DQpin)isopendrainwithaninternalcircuitequivalentto
that shown in Figure6.
The 1-Wire bus requires an external pullup resis-
tor of approximately 5kΩ; thus, the idle state for the
1-Wire bus is high. If for any reason a transaction needs
to be suspended, the bus must be left in the idle state if
the transaction is to resume. Infinite recovery time can
occur between bits so long as the 1-Wire bus is in the
inactive (high) state during the recovery period. If the bus
is held low for more than 480µs, all components on the
bus are reset.
Transaction Sequence
The transaction sequence for accessing the device is as
follows:
1) Step1:Initialization
2) Step2:ROMcommand(followedbyanyrequireddata
exchange)
3) Step 3: MAX31820 Function command (followed by
any required data exchange)
It is very important to follow this sequence every time
the device is accessed, as the device does not respond
if any steps in the sequence are missing or out of order.
Exceptions to this rule are the Search ROM [F0h] and
Alarm Search [ECh] commands. After issuing either of
theseROMcommands,themastermustreturntoStep1
in the sequence.
Initialization
All transactions on the 1-Wire bus begin with an initial-
ization sequence. The initialization sequence consists
of a reset pulse transmitted by the bus master, followed
by presence pulse(s) transmitted by the slave(s). The
presence pulse lets the bus master know that slave
devices (such as the MAX31820) are on the bus and
are ready to operate. Timing for the reset and presence
pulses is detailed in the 1-Wire Signaling section.
Figure 6. Hardware Configuration
RX
4.7kΩ
5µA
TYP
VPU
BUS MASTER
OPEN-DRAIN
PORT PIN 100Ω MOSFET
TX
RX
TX
DQ
MAX31820 1-Wire PORT
RX = RECEIVE
TX = TRANSMIT
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
11
ROM Commands
After the bus master has detected a presence pulse, it
can issue a ROM command. These commands operate
on the unique 64-bit ROM codes of each slave device
and allow the master to single out a specific device if
many are present on the 1-Wire bus. These commands
also allow the master to determine how many and what
types of devices are present on the bus or if any device
has experienced an alarm condition. There are five ROM
commands, and each command is 8 bits long. The master
device must issue an appropriate ROM command before
issuingaMAX31820Functioncommand.Figure7 shows
a flowchart for operation of the ROM commands.
Search ROM [F0h]
When a system is initially powered up, the master must
identify the ROM codes of all slave devices on the bus,
which allows the master to determine the number of
slaves and their device types. The master learns the ROM
codes through a process of elimination that requires the
mastertoperformaSearchROMcycle(i.e.,SearchROM
command followed by data exchange) as many times as
necessary to identify all the slave devices. If there is only
one slave on the bus, the simpler Read ROM command
canbeusedinplaceoftheSearchROMprocess.Fora
detailedexplanationoftheSearchROMprocedure,refer
to ApplicationNote937:Book of iButton Standards. After
everySearchROMcycle,thebusmastermustreturnto
Step1(initialization)inthetransactionsequence.
Read ROM [33h]
This command can only be used when there is one slave
on the bus. It allows the bus master to read the slave’s
64-bitROMcodewithoutusingtheSearchROMproce-
dure. If this command is used when there is more than
one slave present on the bus, a data collision occurs
when all the slaves attempt to respond at the same time.
Match ROM [55h]
The match ROM command, followed by a 64-bit ROM
code sequence, allows the bus master to address a
specific slave device on a multidrop or single-drop bus.
Only the slave that exactly matches the 64-bit ROM code
sequence responds to the function command issued
by the master; all other slaves on the bus wait for a
reset pulse.
Skip ROM [CCh]
The master can use this command to address all devices
on the bus simultaneously, without sending out any ROM
codeinformation.Forexample,themastercanmakeall
devices on the bus perform simultaneous temperature
conversionsby issuing a Skip ROM command followed
by a Convert T [44h] command.
Note that the Read Scratchpad [BEh] command can
followthe Skip ROM command only if there is asingle
slave device on the bus. In this case, time is saved by
allowing the master to read from the slave without send-
ingthedevice’s64-bitROMcode.ASkipROMcommand
followedbyaReadScratchpadcommandcausesadata
collision on the bus if there is more than one slave since
multiple devices attempt to transmit data simultaneously.
Alarm Search [ECh]
The operation of this command is identical to the opera-
tion of the Search ROM command except that only
slaves with a set alarm flag respond. This command
allows the master device to determine if any MAX31820s
experienced an alarm condition during the most recent
temperatureconversion.AftereveryAlarmSearchcycle
(i.e.,AlarmSearchcommandfollowedbydataexchange),
thebusmastermustreturntoStep1(initialization)inthe
transaction sequence. See the Alarm Signaling section
for an explanation of alarm flag operation.
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
12
Figure 7.ROM Commands Flowchart
F0h
SEARCH
ROM?
N
BIT 0
MATCH?
BIT 0
MATCH?
CCh
SKIP
ROM?
N
N
55h
MATCH
ROM?
N
NN
33h
READ
ROM?
N
YY Y
Y
Y
MASTER TX
BIT 0
DEVICE TX
FAMILY CODE
1 BYTE
MASTER TX
FUNCTION COMMAND
DEVICE TX
SERIAL NUMBER
6 BYTES
DEVICE TX
CRC BYTE
MASTER TX
ROM COMMAND
DEVICE TX
PRESENCE PULSE
MASTER TX
RESET PULSE
INITIALIZATION
SEQUENCE
DEVICE TX BIT 0
DEVICE TX BIT 0
MASTER TX BIT 0
MASTER TX
BIT 63
DEVICE TX BIT 63
DEVICE TX BIT 63
MASTER TX BIT 63
BIT 1
MATCH?
BIT 1
MATCH?
NN
BIT 63
MATCH?
BIT 63
MATCH?
NN
YY
ECh
ALARM SEARCH
COMMAND
N
DEVICE(S)
WITH ALARM
FLAG SET?
Y
DEVICE TX BIT
DEVICE TX BIT
MASTER TX BIT 0
Y
Y Y
MASTER TX
BIT 1
DEVICE TX BIT 1
DEVICE TX BIT 1
MASTER TX BIT 1
Y
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
13
Note 1: Forparasite-powereddevices,themastermustenableastrongpulluponthe1-Wirebusduringtemperatureconversions
andcopiesfromthescratchpadtoEEPROM.Nootherbusactivitycantakeplaceduringthistime.
Note 2: The master can interrupt the transmission of data at any time by issuing a reset.
Note 3: All 3 bytes must be written before a reset is issued.
MAX31820 Function Commands
After the bus master has used a ROM command to
address the device with which it wishes to communi-
cate, the master can issue one of the device function
commands. These commands allow the master to write
to and read from the device’s scratchpad memory,
initiate temperature conversions, and determine the
power-supply mode. Table 3 summarizes the device
function commands, and Figure8 illustrates the function
commands.
Convert T [44h]
This command initiates a single temperature conversion.
Following the conversion, the resulting thermal data is
stored in the 2-byte temperature register in the scratch-
pad memory and the device returns to its low-power
idle state. If the device is being used in parasite-power
mode, within 10µs (max) after this command is issued
the master must enable a strong pullup on the 1-Wire bus
for the duration of the conversion (tCONV), as described
in the Powering the MAX31820 section. If the device is
powered by an external supply, the master can issue
read time slots after the Convert T command and the
device responds by transmitting a 0 while the temperature
conversion is in progress and a 1 when the conversion is
done. In parasite-power mode, this notification technique
cannot be used since the bus is pulled high by the strong
pullup during the conversion.
Write Scratchpad [4Eh]
This command allows the master to write 3 bytes of data
to the device’s scratchpad. The first data byte is written
into the TH register (byte 2 of the scratchpad), the second
byte is written into the TL register (byte 3), and the third
byteiswrittenintotheconfigurationregister(byte4).Data
must be transmitted least significant bit first. All three
bytes must be written before the master issues a reset,
or the data may be corrupted.
Read Scratchpad [BEh]
This command allows the master to read the contents
of the scratchpad. The data transfer starts with the least
significant bit of byte 0 and continues through the scratch-
pad until the 9th byte (byte 8 – CRC) is read. The master
can issue a reset to terminate reading at any time if only
part of the scratchpad data is needed.
Copy Scratchpad [48h]
This command copies the contents of the scratchpad
TH, TL and configuration registers (bytes 2, 3, and 4) to
EEPROM.Ifthedeviceisbeingusedinparasitepower
mode, within 10µs (max) after this command is issued
the master must enable a strong pullup on the 1-Wire
bus for at least 10ms, as described in the Powering the
MAX31820 section.
Table 3. MAX31820 Function Command Set
COMMAND DESCRIPTION PROTOCOL 1-Wire BUS ACTIVITY AFTER COMMAND IS
ISSUED
Convert T
(Note1) Initiates temperature conversion. 44h The device transmits conversion status to master
(not applicable for parasite-powered devices).
ReadScratchpad
(Note2)
Reads the entire scratchpad
including the CRC byte. BEh The device transmits up to 9 data bytes to master.
WriteScratchpad
(Note3)
Writes to scratchpad bytes 2, 3,
and 4 (TH, TL,andconguration
registers).
4Eh The master transmits 3 data bytes to the device.
CopyScratchpad
(Note1)
Copies TH, TL,andconguration
register data from the scratchpad to
EEPROM.
48h None.
Recall E2
Recalls TH, TL,andconguration
registerdatafromEEPROMtothe
scratchpad.
B8h The device transmits recall status to the master.
ReadPowerSupply Signalsthedevice’spower-supply
mode to the master. B4h The device transmits supply status to the master.
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
14
Figure 8. MAX31820 Function Commands Flowchart
44h
CONVERT T?
Y
N
PARASITE
POWER?
MASTER TX
FUNCTION COMMAND
DEVICE BEGINS
CONVERSION
MASTER RX
“1s”
MASTER RX
“0s”
YN
MASTER ENABLES
STRONG PULLUP ON DQ
DEVICE CONVERTS
TEMPERATURE
MASTER DISABLES
STRONG PULLUP
MASTER ENABLES
STRONG PULLUP ON DQ
DATA COPIED FROM
SCRATCHPAD TO EEPROM
MASTER DISABLES
STRONG PULLUP
DEVICE
CONVERTING
TEMPERATURE?
Y
N
MASTER RX
“0s”
MASTER RX
“1s”
48h
COPY
SCRATCHPAD?
N
PARASITE
POWER?
YN
YN
MASTER TX TH BYTE
TO SCRATCHPAD
4Eh
WRITE
SCRATCHPAD
?
Y
MASTER TX TL BYTE
TO SCRATCHPAD
MASTER TX CONFIG.
BYTE TO SCRATCHPAD
BEh
READ
SCRATCHPAD
?
Y
Y
MASTER RX DATA BYTE
FROM SCRATCHPAD
MASTER BEGINS DATA
RECALL FROM E2 PROM
RETURN TO INITIALIZATION SEQUENCE
FOR NEXT TRANSACTION
MASTER RX SCRATCHPAD
CRC BYTE
Y
N
N
N
MASTER TX
RESET?
Y
HAVE 8 BYTES
BEEN READ?
B8h
RECALL E2
?
Y
N
B4h
READ
POWER
SUPPLY?
PARASITE
POWER?
NN
MASTER RX
“1s”
MASTER RX
“0s”
COPY
IN PROGRESS?
Y
N
MASTER RX
“1s”
MASTER RX
“0s”
DEVICE
BUSY RECALLING
DATA
?
Y
N
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
15
Recall E2 [B8h]
This command recalls the alarm trigger values (TH and
TL)andconfigurationdatafromEEPROMandplacesthe
data in bytes 2, 3, and 4, respectively, in the scratchpad
memory. The master device can issue read time slots fol-
lowing the Recall E2 command and the device indicates
the status of the recall by transmitting 0 while the recall
is in progress and 1 when the recall is done. The recall
operation happens automatically at power-up, so valid
data is available in the scratchpad as soon as power is
applied to the device.
Read Power Supply [B4h]
The master device issues this command followed by a
read time slot to determine if any devices on the bus are
usingparasitepower.Duringthereadtimeslot,parasite-
powered devices pull the bus low, and externally pow-
ereddevicesletthebusremainhigh.SeethePowering
the MAX31820 section for usage information for this
command.
1-Wire Signaling
The MAX31820 uses a strict 1-Wire communication pro-
tocol to ensure data integrity. Several signal types are
definedbythisprotocol:resetpulse,presencepulse,write
0, write 1, read 0, and read 1. The bus master initiates all
these signals, with the exception of the presence pulse.
Initialization Procedure: Reset and Presence
Pulses
All communication with the device begins with an initial-
ization sequence that consists of a reset pulse from the
master followed by a presence pulse from the device, as
illustrated in Figure9. When the device sends the pres-
ence pulse in response to the reset, it is indicating to the
master that it is on the bus and ready to operate.
During the initialization sequence, the bus master
transmits (TX) the reset pulse by pulling the 1-Wire bus
low for a minimum of 480µs. The bus master then releas-
es the bus and goes into receive mode (RX). When the
busisreleased,the5kΩpullupresistorpullsthe1-Wire
bus high. When the device detects this rising edge, it
waits 15µs to 60µs and then transmits a presence pulse
by pulling the 1-Wire bus low for 60µs to 240µs.
Read/Write Time Slots
The bus master writes data to the device during write time
slots and reads data from the device during read time
slots. One bit of data is transmitted over the 1-Wire bus
per time slot.
Figure 9. Initialization Timing
VPU
1-Wire BUS
MASTER TX RESET PULSE
480µs MINIMUM
MASTER RX
480µs MINIMUM
DEVICE TX PRESENCE PULSE
60µs TO 240µs
DEVICE WAITS
15µs TO 60µs
GND
BUS MASTER PULLING LOW DEVICE PULLING LOW RESISTOR PULLUP
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
16
Write Time Slots
There are two types of write time slots: write-one time
slots and write-zero time slots. The bus master uses a
write-one time slot to write a logic 1 to the device and a
write-zero time slot to write a logic 0 to the device. All write
time slots must be a minimum of 60µs in duration with a
minimum of a 1µs recovery time between individual write
slots. Both types of write time slots are initiated by the
master pulling the 1-Wire bus low (Figure10).
To generate a write-one time slot, after pulling the 1-Wire
bus low, the bus master must release the 1-Wire bus
within 15µs. When the bus is released, the 5kΩ pullup
resistor pulls the bus high. To generate a write-zero time
slot, after pulling the 1-Wire bus low, the bus master must
continue to hold the bus low for the duration of the time
slot (at least 60µs).
The device samples the 1-Wire bus during a window that
lasts from 15µs to 60µs after the master initiates the write
time slot. If the bus is high during the sampling window,
a 1 is written to the device. If the line is low, a 0 is written
to the device.
Read Time Slots
The device can only transmit data to the master when the
master issues read time slots. Therefore, the master must
generate read time slots immediately after issuing a Read
Scratchpad[BEh]orReadPowerSupply[B4h]command,
so that the device can provide the requested data. In
Figure 10. Read/Write Time Slot Timing Diagram
VPU
1-Wire BUS
START
OF SLOT
START
OF SLOT
60µs < TX “0” < 120µs
1µs < tREC < ∞
1µs < tREC < ∞
> 1µs
> 1µs
MASTER SAMPLES MASTER SAMPLES
> 1µs
15µs 15µs 30µs
MASTER WRITE-ZERO SLOT
DEVICE SAMPLES
MIN MAXTYP
DEVICE SAMPLES
MIN MAXTYP
MASTER WRITE-ONE SLOT
MASTER READ-ZERO SLOT MASTER READ-ONE SLOT
GND
VPU
1-Wire BUS
GND
15µs 45µs 15µs
15µs 15µs 30µs
BUS MASTER PULLING LOW DEVICE PULLING LOW RESISTOR PULLUP
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
17
addition, the master can generate read time slots after
issuing Convert T [44h] or Recall E2[B8h]commandsto
find out the status of the operation, as explained in the
Powering the MAX31820 section.
All read time slots must be a minimum of 60µs in duration
with a minimum of a 1µs recovery time between slots. A
read time slot is initiated by the master device pulling the
1-Wire bus low for a minimum of 1µs and then releasing
the bus (Figure 10). After the master initiates the read
time slot, the device begins transmitting a 1 or 0 on the
bus. The device transmits a 1 by leaving the bus high and
transmits a 0 by pulling the bus low. When transmitting
a 0, the device releases the bus by the end of the time
slot, and the bus is pulled back to its high idle state by
the pullup resister. Output data from the device is valid
for 15µs after the falling edge that initiated the read time
slot. Therefore, the master must release the bus and then
sample the bus state within 15µs from the start of the slot.
Figure 11 illustrates that the sum of tINIT, tRC, and
tSAMPLE must be less than 15µs for a read time slot.
Figure12 shows that system timing margin is maximized
by keeping tINIT and tRC as short as possible and by
locating the master sample time during read time slots
towards the end of the 15µs period.
Figure 11. Detailed Master Read-One Timing
Figure 12. Recommended Master Read-One Timing
VIH OF MASTER
MASTER SAMPLES
VPU
1-Wire BUS
GND
15µs
tINIT > 1µs tRC
BUS MASTER PULLING LOW RESISTOR PULLUP
VPU
VIH OF MASTER
tINIT =
SMALL
tRC =
SMALL
MASTER SAMPLES
15µs
1-Wire BUS
GND
BUS MASTER PULLING LOW RESISTOR PULLUP
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
18
Operation Examples
Example 1
In Table 4 there are multiple devices on the bus using
parasite power. The bus master initiates a temperature
conversion in a specific MAX31820 and then reads its
scratchpad and recalculates the CRC to verify the data.
Example 2
In Table 5 there is only one device on the bus using
parasite power. The master writes to the TH, TL, and
configuration registers in the device’s scratchpad and
then reads the scratchpad and recalculates the CRC to
verify the data. The master then copies the scratchpad
contentstoEEPROM.
Table 4. Operation Example 1
Table 5. Operation Example 2
MASTER
MODE
DATA
(LSB FIRST) COMMENTS
Tx Reset Master issues reset pulse.
Rx Presence Devicesrespondwithpresencepulse.
Tx 55h Master issues Match ROM command for desired address.
Tx 64-bit ROM code Master sends device ROM code.
Tx 44h Master issues Convert T command.
Tx DQlineheldhighby
strong pullup MasterappliesstrongpulluptoDQforthedurationoftheconversion(tCONV).
Tx Reset Master issues reset pulse.
Rx Presence Devicesrespondwithpresencepulse.
Tx 55h Master issues Match ROM command.
Tx 64-bit ROM code Master sends device ROM code.
Tx BEh MasterissuesReadScratchpadcommand.
Rx 9 data bytes
Master reads entire scratchpad including CRC. The master then recalculates the CRC of the
rst8databytesfromthescratchpadandcomparesthecalculatedCRCwiththereadCRC
(byte9).Iftheymatch,themastercontinues;ifnot,thereadoperationisrepeated.
MASTER
MODE
DATA
(LSB FIRST) COMMENTS
Tx Reset Master issues reset pulse.
Rx Presence Devicerespondswithpresencepulse.
Tx CCh MasterissuesSkipROMcommand.
Tx 4Eh MasterissuesWriteScratchpadcommand.
Tx 3 data bytes Master sends 3 data bytes to the scratchpad (TH, TL,andcongurationregisters).
Tx Reset Master issues reset pulse.
Rx Presence Devicerespondswithpresencepulse.
Tx CCh MasterissuesSkipROMcommand.
Tx BEh MasterissuesReadScratchpadcommand.
Rx 9 data bytes
Master reads entire scratchpad including CRC. The master then recalculates the CRC of the
rst8databytesfromthescratchpadandcomparesthecalculatedCRCwiththereadCRC
(byte9).Iftheymatch,themastercontinues;ifnot,thereadoperationisrepeated.
Tx Reset Master issues reset pulse.
Rx Presence Devicerespondswithpresencepulse.
Tx CCh MasterissuesSkipROMcommand.
Tx 48h MasterissuesCopyScratchpadcommand.
Tx DQlineheldhighby
strong pullup MasterappliesstrongpulluptoDQforatleast10mswhilecopyoperationisinprogress.
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
19
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
PART TEMP RANGE PIN-PACKAGE
MAX31820MCR+ -55°C to +125°C 3 TO-92 (straight leads)
MAX31820MCR+T -55°C to +125°C 3 TO-92 (formed leads)
MAX31820SLMCR+T -55°C to +125°C 3 TO-92 (straight leads)
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
3 TO-92 (straight leads) Q3+1 21-0248 —
3 TO-92 (formed leads) Q3+4 21-0250 —
MAX31820 1-Wire Ambient Temperature Sensor
www.maximintegrated.com Maxim Integrated
│
20
Package Information
Forthelatestpackageoutlineinformationandlandpatterns(footprints),goto www.maximintegrated.com/packages.Notethata“+”,
“#”,or“-”inthepackagecodeindicatesRoHSstatusonly.Packagedrawingsmayshowadifferentsuffixcharacter,butthedrawing
pertainstothepackageregardlessofRoHSstatus.
Ordering Information
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 6/13 Initial release —
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
MAX31820 1-Wire Ambient Temperature Sensor
© 2013 MaximIntegratedProducts,Inc.
│
21
Revision History
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Mouser Electronics
Authorized Distributor
Click to View Pricing, Inventory, Delivery & Lifecycle Information:
Maxim Integrated:
MAX31820SLMCR+T MAX31820MCR+ MAX31820MCR+T