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 TMP125 
 Temperature sensors 

Digital temperature sensor with SPI-compatible interface, offering reliable and accurate measurements for industrial environments.

 Maximum precision
+/- 1,0°K

 Minimum temperature
-55°C

 Maximum temperature
+125°C

 Minimum dimensions
3 x 3 x 1

Response time

Fast

 Drift

Low

 Self-warming
Low

Price
Medium

What is a TMP125 sensor ?Operating principleTechnical SpecificationsWiring ConfigurationSelf-warmingApplication areas

What is a TMP125 sensor ?

The TMP125 is a 12-bit SPI digital temperature sensor developed by Texas Instruments.

It directly converts ambient temperature into digital data, without external components.

Compact, accurate, and fast, it is perfect for embedded systems, electronic boards, and industrial thermal monitoring.

Operating principle

The TMP125 measures temperature through an integrated diode whose voltage varies with temperature.

This voltage is converted by a 12-bit internal ADC and then transmitted via SPI.

The conversion is signed in two's complement (MSB = sign bit).

T(°C) = Value x 0,0625

Technical specifications

Parameter
 Typical value
Resolution 12 bits (0,0625 °C / LSB)
Measurement range −55 → +125 °C

Precision

±1,0 K (typ.)

Interface

SPI (read-only)

Conversion time

120–160 ms

Max. SPI Frequency

5 MHz

Power supply voltage

2,7 → 5,5 V

Typical current

250 µA

Sleep mode

< 1 µA

Case

SOT-23-6

Annual drift

±0,2 K/year

Wiring Configuration

Brooch Name

Function

1

 CS

Chip Select (active low)
2 SO

SPI Output (MISO)
3 SCK

SPI Clock

4

V+

Power Supply (2.7–5.5 V)

5

GND

Mass

6

NC

Not connected

Self-warming

Almost zero thanks to an internal current < 250 µA.

The TMP125 can be placed directly in contact with a component to be monitored (MOSFET, CPU, PCB, etc.).

Application areas

⚙️ Thermal surveillance of electronic boards

🔋 Thermal management of batteries or DC/DC converters

🧠 Monitoring of microcontrollers, FPGAs, or ASICs

💡 Industrial or environmental instrumentation

🧱 Low-power embedded systems







Should I choose a TMP125 sensor ?

Strengths points

  • ⚙️ Direct digital output
         → The TMP125 delivers a pre-converted and calibrated SPI value, without the need for an amplifier or linearization. A true “plug & measure.”
  • 🎯 Stable accuracy and low drift
         → With an accuracy of ±1 K and a drift of less than ±0.2 K/year, it ensures lasting stability, even in critical systems.
  • 💡 SOT-23 miniature format
         → Its ultra-compact size allows for direct integration with the components to be monitored, perfect for onboard thermal management.
TMP125 sensors

Weaknesses points

  • 🌡️ Limited measurement range
         → Limited to −55 → +125 °C, this sensor is not suitable for very high temperature environments (oven, extrusion, etc.).
  • 🔋 Unidirectional communication
         → The SPI bus is read-only, with no command or dynamic configuration (unlike some modern I²C sensors).
  • 💰 Little interest in multi-sensor systems
    → Each TMP125 requires its own CS line, which complicates the wiring when exceeding 2 or 3 sensors.

Useful information

Here is some useful information regarding the TMP125 sensors.

The TMP125 is a 12-bit signed digital temperature sensor with a fixed resolution of 0.0625 °C / LSB.

It directly converts the ambient temperature into digital data via an integrated diode and an onboard ADC.

Parameter Typical value
Resolution 12 bits (0,0625 °C / LSB)
Measurement range
 −55 → +125 °C
Precision
 ±1,0 K (−25 → +100 °C)
Annual drift
 ±0,2 K
Conversion time
 120 → 160 ms
Power supply voltage
 2,7 → 5,5 V
Consumption
 250 µA typical
Interface
 SPI (read-only)
Max. SPI Frequency
 5 MHz

🔹 Notes:

  • Each conversion yields a signed value in 12 bits (2’s complement).
  • No external calibration required.
  • The internal noise is less than 0.05 °C RMS.

During a 16-bit SPI read, the 12 most significant bits contain the temperature.

The value is signed, with the MSB (bit 15) indicating the sign (0 = positive, 1 = negative).

🔹 SPI word structure (16 bits)

Bit(s) Name
 Description
[15] Sign
 0 = + / 1 = −
[14 → 3] Temperature (12 bits) Value × 0.0625 °C
[2 → 0] Reserved
 0
🔹 Conversion equation

T (°C) = Valeur₁₂b × 0,0625


Practical example:

SPI reading → 0x07D0

0x07D0 = 2000₁₀ 

T = 2000 × 0,0625 = 125,0 °C

✅ Measured temperature = 125 °C

The TMP125 easily integrates with any microcontroller that has an SPI interface (Arduino, STM32, ESP32, Raspberry Pi…).

It only requires 3 active lines: CS, SCK, and SO (MISO).

🔹 Typical components

Component
 Function
TMP125 Digital temperature sensor SPI
Microcontroller (3.3 or 5 V)
 Master SPI
Pull-up resistances (optional)
 CS stability and clock
Supply
 2,7–5,5 V
100 nF capacitor
 Decoupling near the sensor
🔹 Functional diagram (ASCII)
        +3.3V / +5V
             │
         [TMP125]
             │
        SO ────► MISO (MCU)
        SCK ◄─── CLK  (MCU)
        CS  ◄─── GPIO (MCU)
        GND ───── GND

💡 Multiple TMP125 devices can be connected on the same SPI bus, each with its own CS line.

🔹 Operating Principle

1️⃣ The microcontroller pulls CS low to initiate a read.

2️⃣ The TMP125 sends 16 bits: temperature on 12 bits + reserved bits.

3️⃣ The MCU calculates the temperature: T=value×0.0625T = value × 0.0625T=value×0.0625.

4️⃣ The sensor returns to automatic sleep mode to save energy.

Advantage Description
🧠 Direct digital lecture Integrated conversion and linearization
⚙️ Universal SPI Interface Easy to interface, quick reading
🎯 Good accuracy ±1 K Sufficient for industrial monitoring
🔋 Low consumption (250 µA) Perfect for battery systems
💡 Miniature and reliable Easy integration on electronic board
🔧 No calibration required Data ready to use

 We integrate any sensor into any probe 

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 Slot

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Stick-in

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Thread

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Jacketed

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PCBA design

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Winding

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