MAX31850KATB-T View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX31850KATB-T

Cold-Junction Compensated, 1-Wire Thermocouple-to-Digital Converters

Maxim Integrated 

MAX31850/MAX31851

Cold-Junction Compensated, 1-Wire

Thermocouple-to-Digital Converters

MSb

8-BIT

CRC CODE

MSb

LSb MSb

Figure 3. 64-Bit ROM Code

48-BIT SERIAL NUMBER

LSb

8-BIT FAMILY CODE

(3Bh)

LSb MSb

LSb

BYTE 0

BYTE 1

BYTE 2

BYTE 3

BYTE 4

BYTE 5

BYTE 6

BYTE 7

BYTE 8

SCRATCHPAD (POWER-UP STATE SHOWN IN PARENTHESES)

COLD-JUNCTION-COMPENSATED THERMOCOUPLE TEMPERATURE LSB AND FAULT STATUS (00h)

COLD-JUNCTION-COMPENSATED THERMOCOUPLE TEMPERATURE MSB (00h)

INTERNAL (COLD JUNCTION) TEMPERATURE AND FAULT STATUS LSB (00h)

INTERNAL (COLD JUNCTION) TEMPERATURE MSB (00h)

CONFIGURATION REGISTER*

RESERVED (FFh)

RESERVED (FFh)

RESERVED (FFh)

CRC

*THE LOWER 4 BITS (AD[3:0]) OF THE CONFIGURATION REGISTER ARE HARDWIRED THROUGH AD0–AD3.

Figure 4. Memory Map

In some situations the bus master might not know whether

the devices on the bus are parasite powered or powered

by external supplies. The master needs this information

to determine if the strong bus pullup should be used dur-

ing temperature conversions. To get this information, the

master can issue a Skip ROM [CCh] command, followed

by a Read Power Supply [B4h] command, followed by a

read time slot. During the read time slot, parasite-pow-

ered devices pull the bus low, and externally powered

devices let the bus remain high. If the bus is pulled low,

the master knows that it must supply the strong pullup on

the 1-Wire bus during temperature conversions.

64-Bit ROM Code

Each device contains a unique 64-bit code stored in ROM

(Figure 3). The least significant 8 bits of the ROM code

contain the device’s 1-Wire family code, 3Bh. The next 48

bits contain a unique serial number. The most significant

8 bits contain a cyclic redundancy check (CRC) byte that

is calculated from the first 56 bits of the ROM code. See

the CRC Generation section for a detailed explanation

of the CRC bits. The 64-bit ROM code and associated

ROM function control logic allow the device to operate as

a 1-Wire device using the protocol detailed in the 1-Wire

Bus System section.

Scratchpad

The device’s scratchpad is organized as shown

in Figure 4. All memory commands are described

in detail in the MAX31850/MAX31851 Function

Commands section.

Byte 0 and byte 1 of Scratchpad contain the least sig-

nificant byte and the most significant byte of the thermo-

couple temperature register, respectively. Bytes 2 and 3

contain the LSB and MSB of the internal (cold-junction)

temperature value, as well as fault status. Byte 4 con-

tains the configuration information. Bytes 5, 6, and 7 are

reserved for internal use by the device and cannot be

overwritten; these bytes return all ones when read.

Byte 8 of Scratchpad is read-only and contains the CRC

code for bytes 0–7 of the scratchpad. The device gener-

ates this CRC using the method described in the CRC

Generation section.

Maxim Integrated

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