LTC2983_15 Datasheet, PDF (69/72 Pages) Linear Technology – Multi-Sensor High Accuracy Digital Temperature Measurement System

LTC2983
Custom Thermistors
Table 83. Custom Steinhart-Hart Channel Assignment Data
CONFIGURATION
FIELD
DESCRIPTION # BITS BINARY
DATA
MEMORY
ADDRESS 210
MEMORY
ADDRESS 211
MEMORY
ADDRESS 212
MEMORY
ADDRESS 213
(1) Thermistor Type
Custom
5
Steinhart-Hart
11010 1 1 0 1 0
(2) Sense Resister
Channel Pointer
CH₄
5 00100
00100
(3) Sensor
Configuration
Single-Ended 3
100
100
(4) Excitation Current
1µA
4
0011
0011
Not Used
Set These Bits 2
00
to 0
000
(5) Custom Thermistor Start Address 6 011110
Data Pointer
= 30
0 1 1 11 0
(5) Custom Steinhart- Fixed at Six
Hart Length Always 32-Bit Words
Set to 0
6 000000
0 0 00 0 0
A custom thermistor tied to CH5, with a sense resistor on
CH3/4, is programmed with the channel assignment data
shown in Table 83 (refer to Figure 24 for a similar format).
In this case the custom data begins at memory location
0x300 (starting address is 30). The starting address
(offset from 0x250) is entered in the custom thermistor
data pointer field of the channel assignment data. The data
length (set to 0) is always six 32-bit floating point words.
The LTC2983 includes many flexible, software configurable
input modes. In order to share four common inputs among
all four sensor types each sensor requires specific con-
figuration bits (see Table 84). 3-Wire RTDs are configured
with shared R_SENSE, 4-Wire RTDs and thermistors are
configured as shared and/or rotated, thermocouples are
configured differential with internal ground, and diodes
are configured as single-ended.
Universal Sensor Hardware
The LTC2983 can be configured as a universal temperature
measurement device. Up to four sets of universal inputs
can be applied to a single LTC2983. Each of these sets can
directly digitize a 3-wire RTD, 4-Wire RTD, Thermistor, or
thermocouple without changing any on board hardware
(see Figure 42). Each sensor can share the same four ADC
inputs and protection/filtering circuitry are configured using
software changes (new channel assignment data) only.
One sense resistor and cold junction sensor are shared
among all four banks of sensors.
Table 84. Sensor Configuration for Universal Hookup
SENSOR TYPE CONFIGURATION CONFIGURATION SEE TABLE
OPTIONS
BITS
3-WIRE RTD
Share
B18 = 1, B19 = 0 Table 28
4-WIRE RTD
Share
B18 = 1, B19 = 0 Table 28
4-WIRE RTD
Rotate
B18 = 0, B19 = 1 Table 28
Thermistor
Share
B19 = 0, B20 = 1 Table 52
Thermistor
Rotate
B19 = 1, B20 = 0 Table 52
Thermocouple Single-Ended
B21 = 1
Table 14
Diode
Single-Ended
B26 = 1
Table 17
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