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MAX31722/MAX31723

Digital Thermometers and Thermostats

with SPI/3-Wire Interface

19-5629; Rev 0; 11/10

General Description

The MAX31722/MAX31723 digital thermometers and

thermostats with an SPI™/3-wire interface provide tem-

perature readings that indicate the device temperature.

No additional components are required; the devices

are truly temperature-to-digital converters. Temperature

readings are communicated from the device over an

SPI interface or a 3-wire serial interface. The choice of

interface is selectable by the user. For applications that

require greater temperature resolution, the user can

adjust the readout resolution from 9 to 12 bits. This is

particularly useful in applications where thermal runaway

conditions must be detected quickly. The thermostat has

a dedicated open-drain output (TOUT). Two thermostat

operating modes, comparator and interrupt, control ther-

mostat operation based on user-defined nonvolatile trip

points (T

HIGH

and T

LOW

). Both devices feature a 1.7V to

3.7V supply rail.

Applications

Networking Equipment

Cellular Base Stations

Industrial Equipment

Any Thermally Sensitive Systems

Features

S Temperature Measurements Require No External

Components

S Measures Temperatures from -55NC to +125NC

S MAX31722 Thermometer Accuracy is ±2.0NC

S MAX31723 Thermometer Accuracy is ±0.5NC

S Thermometer Resolution is Configurable from 9

to 12 Bits (0.5NC to 0.0625NC Resolution)

S Thermostat Output with User-Defined Nonvolatile

Thresholds

S Data is Read from/Written to by SPI (Mode 0 and 2)

or 3-Wire Serial Interface

S 1.7V to 3.7V Power-Supply Range

S Available in 8-Pin µMAX

Package

Ordering Information

SPI is a trademark of Motorola, Inc.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

+Denotes a lead(Pb)-free/RoHS-compliant package.

T = Tape and reel.

Functional Diagram

MAX31722

MAX31723

OVERSAMPLING

MODULATOR

CONFIGURATION/

STATUS REGISTER

PRECISION

REFERENCE

I/O CONTROL

AND

INPUT SENSE

DIGITAL

DECIMATOR

SDI

SCLK

SDO

SERMODE

GND

TOUT

TEMPERATURE

HIGH

AND T

LOW

REGISTERS

THERMOSTAT

COMPARATOR

PART TEMP RANGE PIN-PACKAGE

MAX31722MUA+

-55NC to +125NC 8 FMAX

MAX31722MUA+T

-55NC to +125NC 8 FMAX

MAX31723MUA+

-55NC to +125NC 8 FMAX

MAX31723MUA+T

-55NC to +125NC 8 FMAX

Summary of content (15 pages)

PAGE 1
9-5629; Rev 0; 11/10 Digital Thermometers and Thermostats with SPI/3-Wire Interface The MAX31722/MAX31723 digital thermometers and thermostats with an SPI™/3-wire interface provide temperature readings that indicate the device temperature. No additional components are required; the devices are truly temperature-to-digital converters. Temperature readings are communicated from the device over an SPI interface or a 3-wire serial interface. The choice of interface is selectable by the user.
PAGE 2
MAX31722/MAX31723 Digital Thermometers and Thermostats with SPI/3-Wire Interface ABSOLUTE MAXIMUM RATINGS Voltage Range on VDD Relative to GND...............-0.3V to +6.0V Voltage Range on Any Other Pin Relative to GND....-0.3V to +6.0V Continuous Power Dissipation (TA = +70NC) FMAX (derate 4.5mW/NC above +70NC).......................362mW EEPROM Programming Temperature Range.. ...-40NC to +85NC Operating Junction Temperature Range.......... -55NC to +125NC Storage Temperature Range.......................
PAGE 3
Digital Thermometers and Thermostats with SPI/3-Wire Interface MAX31722/MAX31723 AC ELECTRICAL CHARACTERISTICS: 3-WIRE INTERFACE (VDD = 1.7V to 3.7V, TJ = -55NC to +125NC, unless otherwise noted.
PAGE 4
MAX31722/MAX31723 Digital Thermometers and Thermostats with SPI/3-Wire Interface CE tCC SCLK tCCZ tCDH tCDZ tCDD tCDD tDC A0 I/O* A1 A7 D0 WRITE ADDRESS BYTE D1 READ DATA BIT *I/O IS SDI AND SDO CONNECTED TOGETHER. Figure 1. Timing Diagram: 3-Wire Read Data Transfer tCWH CE tCC tCCH tR tCL tF SCLK tCDH tCH tDC I/O* A0 A1 WRITE ADDRESS BYTE *I/O IS SDI AND SDO CONNECTED TOGETHER. Figure 2.
PAGE 5
Digital Thermometers and Thermostats with SPI/3-Wire Interface MAX31722/MAX31723 CE tCC SCLK tCDD tCDD tCDH tDC SDI A7 A6 A0 tCDZ SDO D7 D6 WRITE ADDRESS BYTE D1 D0 READ DATA BYTE NOTE: SCLK CAN BE EITHER POLARITY, TIMING SHOWN FOR CPOL = 1. Figure 3. Timing Diagram: SPI Read Data Transfer tCWH CE tCC tR tCL tCCH tF SCLK tCDH tCH tCDH tDC SDI A7 A6 WRITE ADDRESS BYTE A0 D7 D0 WRITE DATA BYTE NOTE: SCLK CAN BE EITHER POLARITY, TIMING SHOWN FOR CPOL = 1. Figure 4.
PAGE 6
Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) TEMPERATURE CONVERSION ACTIVE SUPPLY CURRENT vs. TEMPERATURE 1.4 VDD = 3.7V 1.2 1.0 ICC (µA) 800 VDD = 3.0V 600 400 VDD = 3.7V VDD = 1.7V 0.8 VDD = 3.0V 0.6 0.4 200 VDD = 1.7V 0.2 0 0 -55 -35 -15 5 25 45 65 -55 -35 -15 85 105 125 0.5 12-BIT TEMPERATURE CONVERSIONS VDD = 3.0V 0.4 0.3 3σ 0.2 0.1 0 -0.1 -0.2 -3σ -0.3 -0.4 -0.
PAGE 7
Digital Thermometers and Thermostats with SPI/3-Wire Interface MAX31722/MAX31723 Pin Configuration TOP VIEW TOUT 1 CE 2 SCLK 3 GND 4 + MAX31722 MAX31723 8 VDD 7 SERMODE 6 SDI 5 SDO µMAX Pin Description PIN NAME 1 TOUT FUNCTION 2 CE 3 SCLK Serial-Clock Input. Used to synchronize data movement on the serial interface for either SPI or 3-wire interfaces. 4 GND Ground. Ground connection. 5 SDO Serial-Data Output.
PAGE 8
MAX31722/MAX31723 Digital Thermometers and Thermostats with SPI/3-Wire Interface Measuring Temperature mode is ideal for power-sensitive applications. Details on how to change the setting after power-up are contained in the Programming section. The core of the devices’ functionality is its direct-to-digital temperature sensor. The devices measure temperature through the use of an on-chip temperature measurement technique with a -55NC to +125NC operating range.
PAGE 9
Digital Thermometers and Thermostats with SPI/3-Wire Interface The devices’ thermostat can be programmed to power up in either comparator mode or interrupt mode, which activate and deactivate the open-drain thermostat output (TOUT) based on user-programmable trip points (THIGH and TLOW). The THIGH and TLOW registers contain Celsius temperature values in two’s complement format and are stored in EEPROM memory.
PAGE 10
MAX31722/MAX31723 Digital Thermometers and Thermostats with SPI/3-Wire Interface In either mode, once TOUT has been deactivated, it is only reactivated when the measured temperature falls below the TLOW value. Thus, this interrupt/clear process is cyclical between THIGH and TLOW events (i.e, THIGH, clear, TLOW, clear, THIGH, clear, TLOW, clear, etc.). Figure 6 illustrates the thermostat interrupt mode operation. Table 2.
PAGE 11
Digital Thermometers and Thermostats with SPI/3-Wire Interface BIT 2 R1: Thermostat resolution bit 1. Factory power-up state = 0 and is stored in nonvolatile memory. Sets the conversion resolution (see Table 4). BIT 1 R0: Thermostat resolution bit 0. Factory power-up state = 0 and is stored in nonvolatile memory. Sets the conversion resolution (see Table 4). BIT 0 SD: Factory power-up state = 1. The user has read/write access to the SD bit, which is stored in nonvolatile memory.
PAGE 12
MAX31722/MAX31723 Digital Thermometers and Thermostats with SPI/3-Wire Interface CPOL = 1 CE SHIFT INTERNAL STROBE SHIFT INTERNAL STROBE SCLK CPOL = 0 CE SCLK NOTE: CPOL IS A BIT THAT IS SET IN THE MICROCONTROLLER’S CONTROL REGISTER. Figure 7. Serial Clock as a Function of Microcontroller Clock Polarity (CPOL) Address and Data Bytes Address and data bytes are shifted MSB first into the serial-data input (SDI) and out of the serial-data output (SDO).
PAGE 13
Digital Thermometers and Thermostats with SPI/3-Wire Interface MAX31722/MAX31723 CE SCLK SDI A7 SDO A6 A5 A4 A3 A2 A1 A0 HIGH-Z D7 D6 D5 D4 D3 D2 D1 D0 D7 D6 D5 D4 D3 D2 D1 D0 Figure 8. SPI Single-Byte Read CE SCLK SDI A7 SDO A6 A5 A4 A3 A2 A1 A0 HIGH-Z Figure 9. SPI Single-Byte Write CE SCLK WRITE SDI ADDRESS BYTE SDI ADDRESS BYTE DATA BYTE 0 DATA BYTE 1 DATA BYTE N DATA BYTE 0 DATA BYTE 1 DATA BYTE N READ SDO Figure 10.
PAGE 14
MAX31722/MAX31723 Digital Thermometers and Thermostats with SPI/3-Wire Interface CE SCLK I/O* A0 A1 A2 A3 A4 A5 A6 A7 D0 D1 D2 D3 D4 D5 D6 D7 *I/O IS SDI AND SDO CONNECTED TOGETHER. Figure 11. 3-Wire Single-Byte Transfer CE SCLK I/O* ADDRESS BYTE DATA BYTE 0 DATA BYTE 1 DATA BYTE N *I/O IS SDI AND SDO CONNECTED TOGETHER. Figure 12. 3-Wire Multiple-Byte Burst Transfer Package Information For the latest package outline information and land patterns, go to www.maxim-ic.
PAGE 15
Digital Thermometers and Thermostats with SPI/3-Wire Interface REVISION NUMBER REVISION DATE 0 11/10 DESCRIPTION Initial release PAGES CHANGED — Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.