MCP9808 | GUILCOR SENSORS

MCP9808
Temperature sensors

High-accuracy temperature sensor with I²C interface, ideal for precision measurement and industrial monitoring.

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 18

Typical current
10µA(active)

Price
Low

What is a MCP9808 sensor ?

The MCP9808 is a high-accuracy digital temperature sensor with an I²C interface, designed by Microchip Technology.

Highly precise, programmable, and with low power consumption, it is ideal for industrial applications, medical devices, and embedded electronic systems requiring fine temperature monitoring (Arduino, ESP32, Raspberry Pi, etc.).

Its operation is based on an integrated bandgap temperature sensor and a 13-bit analog-to-digital conversion (ADC), providing the temperature directly in the form of digital data with a typical accuracy of ±0.25 °C.

Operating principle

The MCP9808 measures internal temperature using a bandgap reference whose voltage varies linearly with temperature (highly stable principle, less sensitive to drifts than a simple diode).

This voltage is converted by a ΔΣ (Delta-Sigma) converter into a 13-bit signed digital value, transmitted via the I²C bus.

T(°C) = Binary code x 0,0625

Each increment (LSB) represents 0.0625 °C (in default resolution mode). The unit communicates on the I²C bus according to the master/slave protocol, with up to 8 selectable addresses (0x18 to 0x1F).

Temperature curve / numerical value (13-bit resolution)

Temperature (°C)	Numerical value (hex)	Binary output (12bits)
-40	0x1C00	1 1100 0000 0000
0	0x0000	0 0000 0000 0000
25	0x0190	0 0001 1001 0000
85	0x5500	0 0101 0101 0000
125	0x07D0	0 0111 1101 0000

💡 Each LSB = 0.0625 °C, with a configurable resolution (0.5 / 0.25 / 0.125 / 0.0625 °C) for fine accuracy.

Principle diagram (I2C connection)

     +3.3V
       │
      [MCP9808]
       │ SDA ───────── A0/A1/A2 (address selection)
       │ SCL ─────────┤── [I²C Microcontroller]
       │ ALERT (option)
       │ GND ─────────┘

💡 The MCP9808 supports up to 8 sensors on the same I²C bus thanks to its 3 address-selection pins (A0, A1, A2).

Application areas

🌡️ High-precision thermal monitoring of industrial systems

🧠 Embedded IoT, smart sensors, and connected gateways

🔋 Server room cooling, UPS, laptops

🧪 Medical instrumentation, laboratory devices, and DAQ systems

Should I choose a MCP9808 sensor ?

Strengths points

🎯 Metrological accuracy (±0.25 K)
→ No calibration required, certified over a wide temperature range.
⚡ Adjustable resolution
→ From 0.5 °C to 0.0625 °C depending on the desired speed.
🧠 Smart Alert Function
→ Allows programmable threshold alerts via internal registers (T_UPPER, T_LOWER, T_CRIT).
🔋 Low consumption and 5V compatibility
→ Perfect for battery-powered embedded systems.

Weaknesses points

💸 SLightly more expensive than the TMP102 / LM75
→ But justified by the factory-calibrated precision.
🌡️ Restricted beach
→ Does not exceed +125 °C — insufficient for extreme environments.
📡 Limited communication to I²C
→No SPI or 1-Wire interface possible.

Useful information

Here is some useful information regarding the MCP9808 sensors.

Main registers (7-bit address: 0x18 → 0x1F)

Adress	Registry Name	Function
0x00	Temperature Register	Contains the measured temperature (13 signed bits)
0x01	Configuration Register	Sleep mode, alerts, resolution
0x02	T_UPPER	High alert threshold
0x03	T_LOWER	Low alert threshold
0x04	T_CRIT	Critical threshold
0x05	Manufacturer ID	Microchip Code (0x0054)
0x06	Device ID / Revision	Sensor identification

I²C Reading Example (pseudo-code)

i2c_start();
i2c_write(0x18 << 1);    // MCP9808 Address (write)
i2c_write(0x05);         // Pointer to the temperature registeri2c_start();
i2c_write((0x18 << 1) | 1); // Lecture
MSB = i2c_read_ack();
LSB = i2c_read_nack();
i2c_stop();

raw = ((MSB & 0x1F) << 8) | LSB;
if (MSB & 0x10) raw -= 8192; // Sign
temp = raw * 0.0625;

Typical integration diagram

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

Pull-up resistors (4.7 kΩ typical) required on SDA and SCL.

Example of configuration (CONFIG register)

Bit	Name	Description
[9:8]	Resolution	00 = 0,5°C / 01 = 0,25°C / 10 = 0,125°C / 11 = 0,0625°C
[7]	Alert enable	Activate the ALERT output
[6]	Alert polarity	0 : active low / 1 : active high
[5:4]	Comparator/Interrupt	Alert mode selection
[2:0]	Shutdown / One-shot / Mode continu	Consumption Management