TMP102 | GUILCOR SENSORS

TMP102
Temperature sensors

Low-power digital temperature sensor with I²C interface, ideal for portable devices and embedded systems.

Maximum precision
+/- 0,5°K

Measurement range
-40 / 125°C

Resolution
12 bits

Power supply voltage
1,4 → 3,6V

Conversion speed

25 to 150mS

I2C adress
0 x 48

Typical current
10µA(active)

Price
Low

What is a TMP102 sensor ?

The TMP102 is a digital temperature sensor with an I²C interface, designed by Texas Instruments.

Compact, precise, and with very low power consumption, it is ideal for embedded applications, connected objects, and compact electronic boards (Arduino, ESP32, Raspberry Pi, etc.).

Its operation is based on an integrated diode sensor and a 12-bit analog-to-digital conversion (ADC), providing the temperature directly in the form of digital data.

Operating principle

The TMP102 measures internal temperature using a PN junction whose voltage varies with temperature (similar principle to a diode thermometer).

This voltage is converted by a ΔΣ (Delta-Sigma) converter into a digital value, transmitted via the I²C bus.

T(°C) = Binare code x 0,0625

Each increment (LSB) represents 0.0625 °C.

The unit communicates on the I²C bus according to the master/slave protocol.

Temperature curve / numerical value (12-bit resolution)

Temperature (°C)	Numerical value (hex)	Binary output (12bits)
-40	0xF580	1111 0101 1000 0000
0	0x0000	0000 0000 0000 0000
25	0x1900	0001 1001 0000 0000
Type 85of case	0x5500	0101 0101 0000 0000
125	0x7D00	0111 1101 0000 0000

💡 Each LSB = 0.0625 °C, which allows for very fine resolution for a compact sensor.

Principle diagram (I2C connection)

     +3.3V
       │
      [TMP102]
       │ SDA ─────────┐
       │ SCL ─────────┤── [I²C Microcontroller]
       │ ALERT (option)
       │ GND ─────────┘

💡 The I²C bus allows multiple sensors to be connected on the same SDA/SCL lines using distinct addresses.

Application areas

🌡️ Thermal surveillance of electronic boards

🧠 Embedded IoT sensors and wearables

🔋 Batteries, servers, laptops

🧪 Precision instrumentation (DAQ, microcontrollers)

Should I choose a TMP102 sensor ?

Strengths points

🔋 Ultra low power consumption
→ Ideal for autonomous objects, it consumes only a few microamperes in standby.
🧠 Simple and universal interface
→ The 1 kΩ NTC is inexpensive, standardized, and compatible with most electronic boards and microcontrollers.
📈 Remarkable precision for its size
→ ±0.5 K accuracy over the useful range, without external calibration.

Weaknesses points

🌡️ Limited beach
→ Works up to about 125 °C, so not suitable for extreme industrial environments.
⚡ Slow conversion
→ Up to 150 ms for a complete measurement at 12 bits, not well suited for ultra-fast measurements.
📡 I²C noise sensitive
→ Requires suitable pull resistors and short lines to avoid communication errors.

Useful information

Here is some useful information regarding the TMP102 sensors.

Main registers (7-bit address: 0x48 → 0x4B)

Address	Registry Name	Function
0x00	Temperature Register	Contains the temperature measurement (12 bits)
0x01	Configuration Register	Defines the resolution, the alert, the sleep mode
0x02	T_LOW Register	Low temperature threshold (alert)
0x03	T_HIGH Register	High temperature threshold (alert)

Application example – Digital reading I²C

i2c_start();
i2c_write(0x48 << 1);   // TMP102 Address (write) 
i2c_write(0x00);        // Pointer to the temperature register
i2c_start();
i2c_write((0x48 << 1) | 1); // Lecture
MSB = i2c_read_ack();
LSB = i2c_read_nack();
i2c_stop();

temp = ((MSB << 4) | (LSB >> 4)) * 0.0625;

💡 The reading is done on two bytes, the conversion to °C is simply calculated using the factor 0.0625.

Typical integration diagram

+3.3V │ [ TMP102 ] │ SDA ───────────┐ │ SCL ───────────┤── MCU I²C │ ALERT (option) │ │ GND ───────────┘

💡 Add two pull-up resistors (4.7 kΩ typical) on SDA and SCL to stabilize the communication.

Example of calculation

If the reading returns:

MSB = 0x1A, LSB = 0x10,

we have:

Température = ((0x1A × 16) + (0x10 >> 4)) × 0,0625 = 26,06 °C

✅ Measured temperature ≈ 26.1 °C