Datasheet

ManualsBrandsSparkfun Electronics ManualsRobot PartsOne-Wire Ambient Temperature Sensor - MAX31820

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

4.7kΩ

GND

MEMORY

CONTROL LOGIC

SCRATCHPAD

8-BIT CRC GENERATOR

CONFIGURATION REGISTER (EEPROM)

TEMPERATURE REGISTER

ALARM HIGH TRIGGER

) REGISTER (EEPROM)

ALARM LOW TRIGGER

) REGISTER (EEPROM)

POWER-

SUPPLY

SENSE

MAX31820 1-Wire Ambient Temperature Sensor

19-6731; Rev 0; 6/13

Block Diagram

Summary of content (21 pages)

PAGE 1
MAX31820 1-Wire Ambient Temperature Sensor General Description Benefits and Features 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.
PAGE 2
MAX31820 1-Wire Ambient Temperature Sensor Absolute Maximum Ratings 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 Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device.
PAGE 3
MAX31820 1-Wire Ambient Temperature Sensor AC Electrical Characteristics (VDD = 3.0V to 3.7V, TA = -55°C to +125°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 9-bit resolution 93.75 10-bit resolution 187.
PAGE 4
MAX31820 1-Wire Ambient Temperature Sensor 1-Wire Timing Diagrams 1-Wire WRITE-ZERO TIME SLOT START OF NEXT CYCLE tSLOT tREC tLOW0 1-Wire READ-ZERO TIME SLOT tSLOT tREC START OF NEXT CYCLE tRDV 1-Wire RESET PULSE RESET PULSE FROM HOST tRSTL tRSTH 1-Wire PRESENCE DETECT PRESENCE DETECT tPDHIGH tPDLOW www.maximintegrated.
PAGE 5
MAX31820 1-Wire Ambient Temperature Sensor Pin Configuration SIDE VIEW FRONT VIEW 1 GND 1 DQ 2 2 VDD 3 3 MAX31820 TO-92 Pin Description PIN NAME FUNCTION 1 GND 2 DQ Data In/Out 3 VDD Optional Power Supply Ground 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.
PAGE 6
MAX31820 1-Wire Ambient Temperature Sensor 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. 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 scratchpad memory and the device returns to its idle state.
PAGE 7
MAX31820 1-Wire Ambient Temperature Sensor 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 TL registers are nonvolatile (EEPROM) so they retain data when the device is powered down.
PAGE 8
MAX31820 1-Wire Ambient Temperature Sensor are taking place, or data is being copied from the scratchpad 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 conversion (tCONV) or data transfer (tWR = 10ms).
PAGE 9
MAX31820 1-Wire Ambient Temperature Sensor Memory The device’s memory is organized as shown in Figure 4. The memory consists of an SRAM scratchpad with nonvolatile EEPROM storage for the high and low alarm trigger 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 memory commands are described in detail in the MAX31820 Function Commands section.
PAGE 10
MAX31820 1-Wire Ambient Temperature Sensor Table 2. Thermometer Resolution Configuration R1 R0 RESOLUTION (BITS) 0 0 9 93.75ms MAX CONVERSION TIME (tCONV/8) 0 1 10 187.5ms (tCONV/4) 1 0 11 375ms (tCONV/2) 1 1 12 750ms (tCONV) POLYNOMIAL = X8 + X5 + X4 + 1 1ST STAGE X0 2ND STAGE X1 3RD STAGE X2 4TH STAGE X3 5TH STAGE X4 6TH STAGE X5 7TH STAGE X6 8TH STAGE X7 X8 INPUT DATA Figure 5.
PAGE 11
MAX31820 1-Wire Ambient Temperature Sensor VPU BUS MASTER MAX31820 1-Wire PORT 4.7kΩ DQ RX TX OPEN-DRAIN PORT PIN RX = RECEIVE TX = TRANSMIT RX 5µA TYP TX 100Ω MOSFET Figure 6. Hardware Configuration 1-Wire Bus System The 1-Wire bus system uses a single bus master to control 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.
PAGE 12
MAX31820 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.
PAGE 13
MAX31820 1-Wire Ambient Temperature Sensor INITIALIZATION SEQUENCE MASTER TX RESET PULSE DEVICE TX PRESENCE PULSE MASTER TX ROM COMMAND 33h READ ROM? N Y 55h MATCH ROM? F0h SEARCH ROM? N Y Y DEVICE TX BIT 0 MASTER TX BIT 0 BIT 0 MATCH? N N DEVICE TX SERIAL NUMBER 6 BYTES DEVICE TX CRC BYTE N Y CCh SKIP ROM? N Y DEVICE TX BIT DEVICE TX BIT 0 DEVICE TX BIT MASTER TX BIT 0 BIT 0 MATCH? DEVICE(S) WITH ALARM FLAG SET? Y N Y DEVICE TX BIT 1 MASTER TX BIT 1 BIT 1 MATCH? ECh ALARM
PAGE 14
MAX31820 1-Wire Ambient Temperature Sensor MAX31820 Function Commands Write Scratchpad [4Eh] After the bus master has used a ROM command to address the device with which it wishes to communicate, 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.
PAGE 15
MAX31820 1-Wire Ambient Temperature Sensor 44h CONVERT T? MASTER TX FUNCTION COMMAND 48h COPY SCRATCHPAD? N N Y N Y MASTER RX “0s” MASTER RX “1s” B4h READ POWER SUPPLY? PARASITE POWER? MASTER RX “1s” COPY IN PROGRESS? N MASTER DISABLES STRONG PULLUP N Y MASTER DISABLES STRONG PULLUP MASTER RX “0s” B8h RECALL E2 ? N MASTER RX “1s” BEh READ SCRATCHPAD ? N Y Y Y N DATA COPIED FROM SCRATCHPAD TO EEPROM DEVICE CONVERTS TEMPERATURE N 4Eh WRITE SCRATCHPAD ? Y MASTER TX TH BYTE TO S
PAGE 16
MAX31820 1-Wire Ambient Temperature Sensor 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 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.
PAGE 17
MAX31820 1-Wire Ambient Temperature Sensor Write Time Slots continue to hold the bus low for the duration of the time slot (at least 60µs). 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.
PAGE 18
MAX31820 1-Wire Ambient Temperature Sensor 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).
PAGE 19
MAX31820 1-Wire Ambient Temperature Sensor Operation Examples Example 2 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. In Table 5 there is only one device on the bus using parasite power.
PAGE 20
MAX31820 1-Wire Ambient Temperature Sensor Ordering Information 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) +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages.
PAGE 21
MAX31820 1-Wire Ambient Temperature Sensor Revision History REVISION NUMBER REVISION DATE 0 6/13 DESCRIPTION Initial release PAGES CHANGED — 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. 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.