Data Sheet

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General Description

The MAX6675 performs cold-junction compensation

and digitizes the signal from a type-K thermocouple.

The data is output in a 12-bit resolution, SPI™-compati-

ble, read-only format.

This converter resolves temperatures to 0.25°C, allows

readings as high as +1024°C, and exhibits thermocou-

ple accuracy of 8LSBs for temperatures ranging from

0°C to +700°C.

The MAX6675 is available in a small, 8-pin SO package.

Applications

Industrial

Appliances

HVAC

Automotive

Features

♦ Direct Digital Conversion of Type -K

Thermocouple Output

♦ Cold-Junction Compensation

♦ Simple SPI-Compatible Serial Interface

♦ 12-Bit, 0.25°C Resolution

♦ Open Thermocouple Detection

MAX6675

Cold-Junction-Compensated K-Thermocouple-

to-Digital Converter (0°C to +1024°C)

________________________________________________________________ Maxim Integrated Products 1

SCKV

N.C.

SOT-

T+

GND

TOP VIEW

MAX6675

Pin Configuration

Vcc

GND

T+

T-

SCK

MICROCONTROLLER

68HC11A8

MISO

SCK

SSB

0.1µF

MAX6675

Typical Application Circuit

19-2235; Rev 1; 3/02

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

SPI is a trademark of Motorola, Inc.

PART TEMP RANGE PIN-PACKAGE

MAX6675ISA -20°C to +85°C 8 SO

Summary of content (8 pages)

PAGE 1
9-2235; Rev 1; 3/02 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) Features The MAX6675 performs cold-junction compensation and digitizes the signal from a type-K thermocouple. The data is output in a 12-bit resolution, SPI™-compatible, read-only format. This converter resolves temperatures to 0.25°C, allows readings as high as +1024°C, and exhibits thermocouple accuracy of 8LSBs for temperatures ranging from 0°C to +700°C.
PAGE 2
MAX6675 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°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
Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) (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
Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) MAX6675 Pin Description PIN NAME 1 GND 2 T- FUNCTION Ground 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. 5 SCK Serial Clock Input 6 CS Chip Select. Set CS low to enable the serial interface. 7 SO Serial Data Output 8 N.C.
PAGE 5
Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) Serial Interface The Typical Application Circuit shows the MAX6675 interfaced with a microcontroller. In this example, the MAX6675 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 SO. Forcing CS low immediately stops any conversion process. Initiate a new conversion process by forcing CS high.
PAGE 6
MAX6675 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) CS SCK SO D14 D15 D13 D12 D11 D10 D9 D7 D8 D6 D5 D4 D3 D0 D2 D1 Figure 1a. Serial Interface Protocol tCSS CS tCH tCL SCK tDV tDO tTR SO D15 D3 D2 D1 D0 Figure 1b. Serial Interface Timing BIT DUMMY SIGN BIT 12-BIT TEMPERATURE READING Bit 15 14 0 MSB 13 12 11 10 9 8 7 THERMOCOUPLE DEVICE STATE INPUT ID 6 5 4 3 2 LSB Figure 2.
PAGE 7
Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) VCC 0.
PAGE 8
Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) SOICN.EPS MAX6675 Package Information 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.