Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsLinear ICsMAX6675ISA+T

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™-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.

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

Applications

● Industrial

● Appliances

● HVAC

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

PART TEMP RANGE PIN-PACKAGE

MAX6675ISA -20°C to +85°C 8 SO

Vcc

GND

T+

T-

SCK

MICROCONTROLLER

68HC11A8

MISO

SCK

SSB

0.1µF

MAX6675

SCKV

N.C.

SOT-

T+

GND

TOP VIEW

MAX6675

MAX6675 Cold-Junction-Compensated K-Thermocouple-

to-Digital Converter (0°C to +1024°C)

19-2235; Rev 2; 4/14

Typical Application Circuit

Pin Conguration

Ordering Information

SPI is a trademark of Motorola, Inc.

EVALUATION KIT AVAILABLE

Summary of content (8 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX6675 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) 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™-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
MAX6675 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°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
MAX6675 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) Pin Description Where: PIN NAME FUNCTION 1 GND 2 T- Alumel Lead of Type-K Thermocouple. Should be connected to ground externally. 3 T+ Chromel Lead of Type-K Thermocouple Ground 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
MAX6675 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) Applications Information 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.
PAGE 6
MAX6675 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) CS SCK SO D15 D14 D13 D12 D10 D11 D9 D7 D8 D6 D5 D4 D2 D3 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 Bit 15 0 12-BIT TEMPERATURE READING 14 MSB 13 12 11 10 9 8 7 6 5 4 3 LSB THERMOCOUPLE INPUT DEVICE ID 2 1 0 0 Threestate STATE Figure 2. SO Output www.
PAGE 7
MAX6675 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) Block Diagram VCC 0.1µF 4 DIGITAL CONTROLLER COLD-JUNCTION COMPENSATION DIODE S5 5 SCK 300kΩ ADC 30kΩ S3 T+ 3 S2 T- 1MΩ S4 S1 2 SO A2 A1 30kΩ 7 6 20pF CS MAX6675 300kΩ REFERENCE VOLTAGE 1 GND Package Information For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages.
PAGE 8
MAX6675 Cold-Junction-Compensated K-Thermocoupleto-Digital Converter (0°C to +1024°C) Revision History REVISION NUMBER REVISION DATE 2 4/14 DESCRIPTION Removed automotive reference PAGES CHANGED 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. Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product.