LTC2983 | GUILCOR SENSORS

LTC2983
Temperature sensors

Multi-sensor high-precision temperature measurement system supporting RTDs, thermocouples, and thermistors via SPI interface.

Maximum precision
+/- 0,1°K

Minimum temperature
-200°C

Maximum temperature
+1800°C

Minimum dimensions
9 x 9 x 1

Response time

Medium

Drift

Low

Self-warming
Low

Price
High

What is a LCT2983 sensor ?

The LTC2983 is a complete 24-bit temperature measurement system, directly managing:

Thermocouples (types B, E, J, K, N, R, S, T),
RTDs (Pt10 to Pt1000, 2/3/4 wire),
NTC/PTC thermistors,
and analog voltage sensors.

It integrates:

a 20-channel multiplexer,
two 24-bit sigma-delta converters,
an integrated linearization processor,
and automatic cold junction compensation.

In short: it replaces an entire measurement and calculation system, directly into a single SPI component.

Operating principle

The LTC2983 measures the voltage or resistance from the selected sensor, then:

1️⃣ converts the data via an ultra-precise 24-bit ADC,

2️⃣ automatically applies ITS-90 or Callendar-Van Dusen linearization,

3️⃣ and directly returns the compensated temperature in °C via SPI.

No external table or equation is required.

Technical Specifications

Parameter	Typical value
Resolution	24 bits
Noise at output	0,3 µV RMS
Precision	±0.1 K (with calibrated sensor)
Supported types	Thermocouple, RTD, NTC, PTC, diode, tension
Number of entries	20 multiplexed channels
Compensation cold-junction	Integrated
Interface	SPI 4 wires, up to 20 MHz
Supply	3,0 → 5,5 V
Consumption	1.5 mA (active measurement)
Case	QFN-48 or LQFP-48
Annual drift	±0,05 K/year

Wiring Configuration

Brooch	Name	Function
1-20	CH0–CH19	Sensor inputs (RTD, TC, NTC...)
21	GND	Mass
22	VREF+	Positive voltage reference
23	VREF-	Negative voltage reference
24	CS	Chip Select
25	SCK	SPI Clock
26	SDI	Incoming data (MOSI)
27	SDO	Outgoing data (MISO)
28	INT	Interrupt signal (data ready)
29-48	VDD / AVDD / DVDD	Power supply 3.3 or 5 V

Self-warming

Thanks to its programmable measurement currents (from 5 µA to 1 mA), the LTC2983 minimizes the self-heating of RTDs and NTCs, ensuring stable measurements even over long periods.

Application areas

⚙️ Multichannel industrial instrumentation

🔬 Thermal calibration benches

🧠 High-precision process control systems

💡 Medical equipment and laboratories

🧱 Centralized monitoring of various sensors (RTD, NTC, thermocouple)

🚀 Embedded applications where reliability = priority

Should I choose a MAX6675 sensor ?

Strengths points

🎯 Absolute versatility
→ The LTC2983 handles all types of temperature sensors: RTD, thermocouples, NTC, PTC, and even diodes. A single component to centralize all thermal measurements of a system.
⚙️ Integrated linearization and compensation
→ It internally applies the ITS-90 and Callendar-Van Dusen equations, with automatic cold junction compensation, eliminating the need for any external software processing.
🧠 Laboratory resolution and precision
→ With its 24 bits and an accuracy of ±0.1 K, it outperforms most external measuring instruments. It is a complete converter + thermal processor on a single chip.

Weaknesses points

💰 High cost and complexity
→ The LTC2983 is not just a simple sensor: it is a complete subsystem. Its price and configuration are only justified in professional or multi-sensor environments.
🧩 Requires advanced software configuration
→ The SPI initialization involves programming the channels, types of sensors, coefficients, and excitation currents. It therefore requires skills in embedded development.
🔋 Consumption and clutter
→ With more than 40 pins and a consumption of 1.5 mA, it is too heavy for small low-energy systems.

Useful information

Here is some useful information regarding the LTC2983 sensors.

Resolution and precision

With more than 40 pins and a consumption of 1.5 mA, it is too heavy for small low-energy systems.

Parameter	Typical value
ADC Resolution	24 bits (0.00006% of full scale)
Absolute precision	±0.1 K (calibrated RTD or thermocouple)
RMS Noise	0,3 µV
Measurement range	−200 → +1800 °C (according to sensor)
Supported types	RTD, thermocouple, NTC/PTC, diode, tension
Compensation cold-junction	Integrated
Excitation current	Programmable (5 µA → 1 mA)
Power supply voltage	3,0 → 5,5 V
Active consumption	1,5 mA
Annual drift	±0,05 K
SPI Interface	Up to 20 MHz

🔹 Remarks:

The LTC2983 directly calculates temperature in °C — no external calculation required.
The effective resolution (ENOB) reaches 23 bits on RTD / NTC.
Factory calibration across the entire analog chain.

Application Example – SPI Reading

The LTC2983 operates as an integrated thermal microprocessor.

The user configures a channel (sensor type, current, compensation, coefficients),

then reads the temperature directly in signed binary on 24 bits.

🔹 SPI read structure (32 bits)

Bits	Name	Description
[31 → 24]	Channel address	Selected sensor
[23 → 0]	Temperature (signed)	Value × scale factor

Simplified equation (RTD or NTC)

T (°C) = Raw value / 1024

Example:

SPI Reading → 0x0001F400

Raw value 0x1F400 = 128000₁₀

T = 128000 / 1024 = 125.0 °C

✅ Measured temperature: 125 °C

🔹 Thermocouple reading with automatic compensation

The LTC2983 simultaneously measures:

the thermocouple voltage,
the internal cold junction temperature (integrated diode),
and then adds the two to provide a directly compensated absolute temperature.

Integration into an electronic system

The LTC2983 connects via 4-wire SPI to any microcontroller (Arduino, STM32, ESP32, Raspberry Pi…).

It can drive up to 20 independent channels, each configured for a different type of sensor.

🔹 Typical components

Component	Function
LTC2983	Multisensor thermal measurement system
Microcontroller / CPU	Lecture SPI and channel configuration
RTD sensors, TC, NTC, PTC, diode	Analog Inputs
Precision resistors 10 kΩ / 0.1 %	RTD References
Capacitors 100 nF / 10 µF	Power filtering
Stable power supply 3.3 or 5 V	Main source
Reference voltage (LTC6655 or equivalent)	Ultra-stable reference 2.5–5 V

🔹 Functional diagram (ASCII)

             +5V
              │
       [RTD / TC / NTC Sensor]
              │
           ┌──────────┐
           │  LTC2983 │
           │──────────│
           │  CH0–CH19 → sensor inputs   │
           │  CS   → GPIO (MCU)             │
           │  SCK  → SPI CLK                │
           │  SDI  → MOSI                   │
           │  SDO  → MISO                   │
           │  INT  → GPIO (data ready)      │
           │  VREF+ / VREF−                 │
           │  GND / AVDD / DVDD             │
           └──────────┘
                 │
           ┌────────────┐
           │ Microcontroller │
           └────────────┘

💡 The channels CH0–CH19 can be configured independently for each type of sensor.

🔹 Operating principle

1️⃣ The microcontroller configures each channel (type, coefficients, current, etc.).

2️⃣ The LTC2983 performs the analog measurement.

3️⃣ It automatically applies linearization and cold-junction compensation.

4️⃣ The MCU directly reads the temperature in °C via SPI.

Practical advantage

Advantage	Description
🧠 Complete multi-sensor measurement system	Supports RTD, TC, NTC, diodes, and voltages
⚙️ Integrated linearization and compensation	No calculation code on MCU
🎯 Laboratory precision ±0.1 K	24-bit ADC and factory calibration
🧩 20 independent channels	Simultaneous reading of multiple sensors
💡 Fast SPI (20 MHz)	Compatible with industrial MCUs and SBCs
🔋 Minimal warm-up	Programmable current 5 µA → 1 mA
🔧 Integrated diagnostics	Short-circuit detection, open sensor, cold-junction error