LTC2995 datasheet(20/90 Pages) AD

20 / 90 page

LTM2985

Rev. 0

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The channel assignment data contains all the necessary

information associated with the specific sensor tied to

that channel (see Table 4). The first five bits determine the

sensor type (see Table 5). Associated with each sensor

are sensor specific configurations. These include point-

ers to cold junction or sense resistor channels, pointers

to memory locations of custom linearization data, sense

resistor values and diode ideality factors. Also included

in this data are, if applicable, the excitation current level,

single-ended/differential input mode, as well as sensor

specific controls. Separate detailed operation sections for

thermocouples, RTDs, diodes, thermistors, analog tem-

perature sensors and sense resistors describe the assign-

ment data associated with each sensor type in more detail.

The LTM2985 demonstration software includes a utility

for checking configuration data and generating annotated

C-code for programming the channel assignment data.

Table 4. Channel Assignment Data

SENSOR TYPE

SENSOR SPECIFIC CONFIGURATION

Channel

Assignment

Memory Location

Configuration Data

Start Address

Configuration Data

Start Address + 1

Configuration Data

Start Address + 2

Configuration Data

Start Address + 3

31 30 29 28 27 26

24 23 22 21

17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

Unassigned

(Default)

Type = 0

Channel Disabled

Thermocouple

Type = 1 to 9

Cold Junction Channel

Assignment [4:0]

SGL=1

DIFF=0

Check

OC Current

[1:0]

0 0 0 0 0

Custom

Address [5:0]

Custom

Length – 1 [5:0]

RTD

Type = 10 to 18 RSENSE Channel Assignment

[4:0]

2, 3, 4 Wire

Excitation

Mode

Excitation

Current [3:0]

Curve

[1:0]

Custom

Address [5:0]

Custom

Length – 1 [5:0]

Thermistor

Type = 19 to 27 RSENSE Channel Assignment

[4:0]

SGL=1

DIFF=0

Excitation

Mode

Excitation Current

[3:0]

0 0

Custom

Address [5:0]

Custom

Length – 1 [5:0]

Diode

Type = 28

SGL=1

DIFF=0

2 to 3

Reading

Avg

Current

[1:0]

Ideality Factor (2, 20) Value from 0 to 4 with 1/1048576 Resolution

All Zeros Use Factory Set Default in ROM

Sense Resistor

Type = 29

Sense Resistor Value (17, 10) Up to 131,072Ω with 1/1024Ω Resolution

Direct ADC

Type = 30

SGL=1

DIFF=0

Table

Mode

Not Used

Custom

Address [5:0]

Custom

Length – 1 [5:0]

Active Analog

Temperature

Sensor

Type = 31

SGL=1

DIFF=0

Not Used

Custom

Address [5:0]

Custom

Length – 1 [5:0]

APPLICATIONS INFORMATION

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