Datasheet

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General Description

The MAX31820PAR ambient temperature sensor pro-

vides 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 addi-

tion, the device derives 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 MAX31820PAR has a unique 64-bit serial code, which

allows multiple MAX31820PAR devices to function on the

same 1-Wire bus. Therefore, it is simple to use one micropro-

cessor 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

● DerivesPowerfromDataLine(ParasitePower);No

LocalPowerSupplyNeeded

● MultidropCapabilitySimplifiesDistributed

Temperature-SensingApplications

● RequiresNoExternalComponents

● 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

● SoftwareCompatiblewiththeDS1822-PARand

DS18B20-PAR

Ordering Information appears at end of data sheet.

For related parts and recommended products to use with this part, refer

to www.maximintegrated.com/MAX31820PAR.related.

1-Wire is a registered trademark of Maxim Integrated Products, Inc.

MAX31820PAR

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 (T

)

ALARM LOW TRIGGER (T

)

MAX31820PAR 1-Wire, Parasite-Power,

Ambient Temperature Sensor

19-6732; Rev 0; 6/13

Block Diagram

Summary of content (21 pages)

PAGE 1
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor General Description The MAX31820PAR 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
MAX31820PAR 1-Wire, Parasite-Power, 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 +100°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
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor AC Electrical Characteristics (VPU = 3.0V to 3.7V, TA = -55°C to +100°C, unless otherwise noted.) (Note 1) PARAMETER Temperature Conversion Time SYMBOL tCONV CONDITIONS TYP MAX UNITS 93.75 10-bit resolution 187.
PAGE 4
MAX31820PAR 1-Wire, Parasite-Power, 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
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor Pin Configuration SIDE VIEW FRONT VIEW GND 1 1 DQ 2 2 N.C. 3 3 MAX31820PAR TO-92 Pin Description PIN NAME 1 GND FUNCTION 2 DQ Data Input/Output. Open-drain, 1-Wire interface pin that provides power to the device when used in parasite power mode (see the Parasite Power section). 3 N.C. Not Connected. Does not connect to internal circuit.
PAGE 6
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor Operation other components to the sensor. As much as practical, avoid copper in the vicinity of the sensor. Measuring Ambient Temperature The device’s core functionality is its direct-to-digital temperature 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.
PAGE 7
MAX31820PAR 1-Wire, Parasite-Power, 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.
PAGE 8
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor 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). No other activity can take place on the 1-Wire bus while the pullup is enabled. 64-Bit Lasered ROM Code Each device contains a unique 64-bit code stored in ROM (Figure 2).
PAGE 9
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor 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.
PAGE 10
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor 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 4. CRC Generator 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.
PAGE 11
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor VPU VPU STRONG PULLUP 1-Wire BUS RX DQ PIN RX 5µA TYP TX MICROPROCESSOR MAX31820PAR 1-Wire PORT 4.7kΩ RX = RECEIVE TX = TRANSMIT 100Ω MOSFET TX Figure 5. Hardware Configuration 1-Wire Bus System The 1-Wire bus system uses a single bus master to control one or more slave devices. The MAX31820PAR is always a slave.
PAGE 12
MAX31820PAR 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
MAX31820PAR 1-Wire, Parasite-Power, 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
PAGE 14
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor MAX31820PAR Function Commands 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
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor 44h CONVERT T? MASTER TX FUNCTION COMMAND 48h COPY SCRATCHPAD? N Y N N Y MASTER ENABLES STRONG PULLUP ON DQ MASTER ENABLES STRONG PULLUP ON DQ DEVICE CONVERTS TEMPERATURE DATA COPIED FROM SCRATCHPAD TO EEPROM MASTER DISABLES STRONG PULLUP MASTER DISABLES STRONG PULLUP B8h RECALL E2 ? N BEh READ SCRATCHPAD ? N Y Y 4Eh WRITE SCRATCHPAD ? Y MASTER TX TH BYTE TO SCRATCHPAD MASTER BEGINS DATA RECALL FROM E2 PROM MASTER TX RESE
PAGE 16
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor 1-Wire Signaling as illustrated in Figure 8. When the device sends the presence pulse in response to the reset, it is indicating to the master that it is on the bus and ready to operate. The MAX31820PAR uses a strict 1-Wire communication protocol 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.
PAGE 17
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor Read/Write Time Slots slots. Both types of write time slots are initiated by the master pulling the 1-Wire bus low (Figure 9). 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. 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.
PAGE 18
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor 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] command, so that the device can provide the requested data. In addition, the master can generate read time slots after issuing a Recall E2 [B8h] command to find out the status of the operation, as explained in the Parasite Power section.
PAGE 19
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor Operation Examples Example 2 Example 1 In Table 4 there are multiple devices on the bus. The bus master initiates a temperature conversion in a specific MAX31820PAR and then reads its scratchpad and recalculates the CRC to verify the data. In Table 5 there is only one device on the bus.
PAGE 20
MAX31820PAR 1-Wire, Parasite-Power, Ambient Temperature Sensor Ordering Information PART TEMP RANGE PIN-PACKAGE MAX31820PARMCR+ -55°C to +125°C 3 TO-92 (straight leads) MAX31820PARMCR+T -55°C to +125°C 3 TO-92 (formed 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
MAX31820PAR 1-Wire, Parasite-Power, 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.