Datasheet

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General Description

The MAX6674 cold-junction-compensation thermocou-

ple-to-digital converter performs cold-junction compensa-

tion and digitizes the signal from a type-K thermocouple.

The data is output in a 10-bit resolution, SPI™-compatible,

read-only format.

This converter resolves temperatures to 0.125°C, allows

readings as high as +128°C, and exhibits thermocouple

accuracy of ±2°C for temperatures ranging from 0°C to

+125°C.

The MAX6674 is available in a small, 8-pin SO package.

Applications

● Industrial

● Appliances

● HVAC

Features

● Cold-Junction Compensation

● Simple SPI-Compatible Serial Interface

● 10 Bit, 0.125°C

● Open Thermocouple Detection

PART TEMP RANGE PIN-PACKAGE

MAX6674ISA -20°C to +85°C 8 SO

Vcc

GND

T+

T-

SCK

MICROCONTROLLER

68HC11A8

MISO

SCK

SSB

0.1µF

MAX6674

SCKV

N.C.

SOT-

T+

GND

TOP VIEW

MAX6674

MAX6674 Cold-Junction-Compensated K-Thermocouple-

to-Digital Converter (0°C to +128°C)

19-2241; Rev 2; 4/14

Typical Application Circuit

Pin Conguration

Ordering Information

Summary of content (8 pages)

PAGE 1
MAX6674 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +128°C) General Description The MAX6674 cold-junction-compensation thermocouple-to-digital converter performs cold-junction compensation and digitizes the signal from a type-K thermocouple. The data is output in a 10-bit resolution, SPI™-compatible, read-only format. This converter resolves temperatures to 0.
PAGE 2
MAX6674 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +128°C) Absolute Maximum Ratings Supply Voltage (VCC to GND)................................. -0.3V to +6V SO, SCK, CS, T-, T+ to GND ......................-0.3V to VCC + 0.3V SO Current .........................................................................50mA ESD Protection (Human Body Model) ........................... ±2000V Continuous Power Dissipation (TA = +70°C) 8-Pin SO (derate 5.88mW/°C above +70°C)................
PAGE 3
MAX6674 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +128°C) Electrical Characteristics (continued) (VCC = +3.0V to +5.5V, TA = -20°C to +85°C, unless otherwise noted. Typical values specified at +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS Output High Voltage VOH ISOURCE = 1.6mA Output Low Voltage VOL ISINK = 1.6mA MIN TYP MAX VCC 0.4 UNITS V 0.4 V 4.
PAGE 4
MAX6674 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +128°C) Pin Description PIN NAME 1 GND FUNCTION Ground For a type-K thermocouple, the voltage changes by 41µV/°C, which approximates the thermocouple characteristic with the following linear equation: VOUT = (41µV/°C) 5 (TR - TAMB) 2 T- Alumel Lead of Type-K Thermocouple. Should be connected to ground externally. 3 T+ Chromel Lead of Type-K Thermocouple 4 VCC Positive Supply. Bypass with a 0.1µF capacitor to GND.
PAGE 5
MAX6674 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +128°C) Applications Information Serial Interface The Typical Application Circuit shows the MAX6674 interfaced with a microcontroller. In this example, the MAX6674 processes the reading from the thermocouple and transmits the data through a serial interface. Force CS low and apply a clock signal at SCK to read the results at S0. Forcing CS low immediately stops any conversion process.
PAGE 6
MAX6674 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +128°C) CS SCK SO D15 D14 D13 D12 D11 D10 D9 D7 D8 D6 D5 D4 D3 D2 D1 D0 Figure 1a. Serial Interface Protocol tCSS CS tCH SCK tCL tDV tDO tTR SO D15 D3 D2 D1 D0 Figure 1b. Serial Interface Timing BIT DUMMY SIGN BIT 10-BIT TEMPERATURE READING Bit 15 14 0 MSB 13 12 11 10 9 8 7 6 5 LSB THERMOCOUPLE INPUT DEVICE ID 4 3 2 0 Three-state STATE 1 0 Figure 2. S0 Output www.
PAGE 7
MAX6674 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +128°C) Block Diagram VCC 0.1µF 4 DIGITAL CONTROLLER COLD-JUNCTION COMPENSATION DIODE S5 5 SCK 300kΩ 3 ADC 10kΩ S3 T+ S2 T2 1MΩ 10kΩ 7 SO A2 A1 S4 S1 6 20pF CS MAX6674 300kΩ REFERENCE VOLTAGE 1 GND Chip Information TRANSISTOR COUNT: 6460 PROCESS: BiCMOS www.maximintegrated.com Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.
PAGE 8
MAX6674 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +128°C) Revision History REVISION NUMBER REVISION DATE 2 4/14 PAGES CHANGED DESCRIPTION No /V OPNs; removed Automotive reference from Applications section 1 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.