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 TCN75A 
 Temperature sensors 

Cost-effective I²C temperature sensor compatible with LM75, suitable for basic thermal management applications.

 Measurement range
-40 / 125°C

 Temperature accuracy
+/- 1,0°K

 Resolution (Rh and T°)
9 to 12 bits

 Power supply voltage
2,7 → 5,5V

Conversion time
240 ms

 Typical current
250 µA(active)

 I²C Speed
0x48

 Price
Low

What is a TCN75A sensor ?Operating principleExample of conversionPrinciple diagram (I2C connection)Application areas

What is a TCN75A sensor ?

The TCN75A is a digital temperature sensor with an I²C interface, fully calibrated and linear, developed by Microchip Technology.

It is a modern equivalent of the LM75, widely used in electronic boards, servers, power supplies, embedded systems, and consumer products.

It offers good accuracy, stability, and SMBus compatibility, all in a compact and cost-effective format.

Operating principle

The TCN75A integrates:

  • a silicon junction temperature sensor,
  • a 12-bit ADC converter,
  • a configuration EEPROM memory,
  • and a programmable alert output (ALERT pin).

The data is transmitted in the form of a signed word (MSB + LSB) according to the formula:

T(°C) = Signed codex / 16

(in 12-bit mode, or 0.0625 °C per LSB)

Example of conversion

Signed hex value Temperature (°C)
0x0000 0,0
0x0100 1,0
0x1900 25,0
0x3200 50,0
0x6400 100,0


💡 Identical format to the LM75 – the drivers are interchangeable.

Principle diagram (I²C connection)

+3.3V
 │
[TCN75A]
 │ SDA ─────────┐
 │ SCL ─────────┤── [I²C Microcontroller]
 │ A0–A2 ───────┘ (address configuration)
 │ ALERT ───────┐ (alert exit)
 │ GND

💡 I²C Address: 0x48 → 0x4F according to A0–A2.

Application areas

💻 Thermal monitoring of CPU / GPU / electronic boards

⚙️ Embedded systems and simple regulation

🔋 Thermal protection in power supplies

🧠 Low-cost IoT projects

🏠 Basic digital thermometers



Should I choose a TCN75A sensor ?

Strengths points

  • 💰 Ultra economical and proven
         → One of the most affordable I²C sensors on the market.
  • ⚙️ Compatible LM75→ Same protocol, same registers — direct replacement without code modification.
  • 🔋 Low consumption
         → Perfect for battery-operated systems or long-term standby.
  • 📡 Configurable address
    • → Up to 8 sensors on the same I²C bus.
TNC75A sensors

Weaknesses points

  • 🎯 Limited precision
         → ±1 K — sufficient for monitoring, insufficient for precision measurements.
  • 📏 Variable resolution
         → From 9 to 12 bits — to be adjusted as needed (and the conversion time).
  • 🌡️ No dynamic calibration
         → A possible long-term drift if exposed to high temperatures for an extended period.

Useful information

Here is some useful information regarding the TCN75A sensors.

Adress (hex) Name
 Function
0x00 Temperature Register Temperature data (2 bytes)
0x01 Configuration Resolution, mode, polarity
0x02 T_HYST Hysteresis threshold
0x03 T_OS Trigger threshold
0x04 Product ID Component ID
0xFF Shutdown / One-shot Energy-saving mode 
i2c_start();
i2c_write(0x48 << 1);
i2c_write(0x00);
i2c_start();
i2c_write((0x48 << 1) | 1);
MSB = i2c_read_ack();
LSB = i2c_read_nack();
i2c_stop();

raw = (MSB << 8) | LSB;
if (raw & 0x8000) raw -= 65536;
temp = raw / 16.0; // 0.0625°C per LSB

✅ Example :

MSB = 0x19, LSB = 0x00 → (0x1900 / 16) = 25,0 °C

3.3V ───────────┐
                │
               [TCN75A]
                │ SDA ───────┐
                │ SCL ───────┤── MCU (Arduino, STM32, ESP32…)
                │ ALERT ─────┘ (heat alert)
                │ GND

💡 The SDA/SCL pull-up resistors (4.7–10 kΩ) are essential.

Bit Name
 Description
[7] One-shot 1 = unique measure
[6] Resolution bit1 Resolution setting
[5] Resolution bit0 9 to 12 bits
[4] Fault queue 1 to 4 samples before alert
[1] Mode 0 = continue / 1 = standby
[0] Polarity Pin polarity ALERT

💡 By default, the sensor starts in continuous 12-bit mode (ready to use).

Temperature (°C) Error (K)
−40 ±1,5
0 ±1,0
25 ±0,75
85 ±1,0
125 ±1,5

💡 The TCN75A is a reliable choice for thermal monitoring and security, not for metrology.

 We integrate any sensor into any probe 

Smooth tube probe

 Smooth tube 

Waterproof probe

 Waterproof

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 Bayonet

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 Slot

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 Atmosphere

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Termal block

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Stick-in

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Thread

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Contact

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Jacketed

PCBA Design

PCBA design

Winding probe

Winding

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