MCP3208 | GUILCOR SENSORS

MCP3208
Temperature sensors

12-bit multi-channel ADC with SPI interface, designed for precise analog signal acquisition in embedded systems.

Maximum precision
+/- 1,0 LSB

Minimum temperature
-40°C

Maximum temperature
+125°C

Minimum dimensions
10 x 10 x 2

Response time

Fast

Drift

Low

Self-warming
Low

Price
Low

What is a MCP3208 sensor ?

The MCP3208 is a 12-bit SPI analog-to-digital converter manufactured by Microchip.

It allows for the transformation of analog signals (voltage) into digital values that can be processed by a microcontroller.

With its 8 independent channels, it can measure:

multiple analog temperature sensors (NTC, amplified Pt100, thermocouple with amplifier),
or voltage signals (0–5 V or 0–3.3 V depending on the power supply).

It is a universal component in Guilcor's data acquisition systems.

Operating principle

The MCP3208 receives an analog signal between 0 and Vref and converts it to 12 bits via a successive approximation ADC.

The result is transmitted serially via the 4-wire SPI interface.

V_IN = (N / 4096) × V_REF

with

N = numerical value (0–4095),
Vref = reference voltage of the converter.

Technical Specifications

Parameter	Typical value
Number of channels	8 simple entries or 4 differential
Resolution	12 bits (1 LSB ≈ 1.22 mV at 5 Vref)
Reference voltage (Vref)	2.5 to 5.0 V
Sampling rate	100,000 samples/s
Interface	SPI (read/write)
Operating current	500 µA typical
Sleep mode	< 1 µA
Differential entry	Yes
Case	DIP-16 / SOIC-16 / TSSOP-16
Gain drift	< ±0,1 % / 25 °C

Wiring Configuration

Brooch	Name	Function
1-8	CH0-CH7	Analog inputs (0–Vref)
9	DGND	Mass density
10	CS/SHDN	Chip Select (SPI)
11	DIN	SPI Input (MOSI)
12	DOUT	SPI Output (MISO)
13	CLK	SPI Clock
14	AGND	Analog mass
15	VREF	Reference voltage
16	VDD	Power supply 2.7–5.5 V

Self-warming

Almost none. The MCP3208 consumes less than 500 µA, making it perfect for low-power or battery-operated systems.

Application areas

⚙️ Analog conversion for RTD, NTC sensors, amplified thermocouples

🧠 Multichannel measurement chains (up to 8 probes)

💡 Acquisition of environmental or industrial data

🧱 Embedded systems with microcontrollers (ESP32, STM32, Arduino)

🔋 Low power projects and wireless monitoring

Should I choose a MCP3208 sensor ?

Strengths points

🎯 8-channel versatility
→ Allows for the simultaneous measurement of up to 8 analog signals, ideal for multi-sensor systems (RTD, NTC, voltage, pressure...).
⚡ Excellent responsiveness
→Ultra-fast conversion time (≤10 µs), perfect for real-time thermal monitoring or fast control loops.
💡 Low consumption and reduced cost
→ A reliable 12-bit precision at a low price: an excellent compromise between performance, simplicity, and energy efficiency.

Weaknesses points

📶 Requires analog conditioning
→ The MCP3208 does not directly read resistive sensors or raw thermocouples, it must be paired with an amplifier or measurement bridge.
🔋 Sensitive to noise on Vref
→ The quality of the reference voltage directly affects the overall accuracy (ensure stable filtering).
🧠 No built-in thermal compensation
→ Unlike a module like the MAX31856, it does not include temperature management, it is up to the user to apply the software correction.

Useful information

Here is some useful information regarding the MCP3208 sensors.

Resolution and precision

The MCP3208 is a 12-bit analog-to-digital converter using a successive approximation (SAR) architecture.

It allows for fast and stable reading of analog signals between 0 and Vref.

Parameter	Typical value
Resolution	12 bits (4096 levels)
Absolute precision	±1 LSB typical
Reference voltage (Vref)	2,5 → 5,0 V
Entry beach	0 → Vref
Sampling rate	Up to 100 ksps
Gain error	±0,1 %
Offset error	< ±1 LSB
Thermal drift	< 1 ppm/°C

🔹 Remarks:

Each bit represents Vref / 4096 volts.
For example, for Vref = 5 V → 1 LSB = 1.22 mV.
No noticeable self-heating (< 0.05 °C).

Application example – Reading an analog sensor

Let's take the example of a Pt100 RTD probe connected to an instrumentation amplifier (INA333) whose output varies from 0 to 5 V.

V_in = N / 4096 × V_ref

N = V_in / V_ref × 4096

Example :

• V_ref = 5.0 V

• V_in = 2.48 V

N = 2.48 / 5.0 × 4096 = 2032

✅ Numeric value = 2032 / 4096 = 49.6% of full scale

The microcontroller then converts this data into temperature according to the sensor's curve.

Integration into an electronic system

The MCP3208 connects to any microcontroller via the 4-wire SPI bus.

It can power up to 8 analog sensors with fast multiplexed conversion.

🔹 Typical components

Component	Function
MCP3208	Analog-to-Digital Converter SPI
Microcontroller (Arduino, ESP32, STM32)	Lecture SPI and processing
Analog sensor (RTD, NTC, etc.)	Source of the signal
Instrumentation amplifier	Voltage adaptation and linearization
Voltage reference (LM4040, ADR03)	Measurement stability
Capacitors 100 nF / 10 µF	Noise filtering on Vref and VDD

🔹 Functional diagram (ASCII)

+5V │ [Analog sensor │ ┌────────────┐ │ Amplifier │ └──────┬───────┘ │ ▼ ┌──────────────┐ │ MCP3208 │ │──────────────│ │ CH0–CH7 ← sensors │ │ CLK → SPI SCK │ │ DOUT → MISO │ │ DIN → MOSI │ │ CS → Chip Select │ │ VREF ← 5V ref │ │ GND → mass │ └──────────────┘ │ ┌────────────┐ │ Microcontroller │ └────────────┘

🔹 Operating Principle

1️⃣ The microcontroller selects the channel to read via SPI.

2️⃣ The MCP3208 converts the analog voltage (0 → Vref) into a 12-bit data.

3️⃣ The digital value is sent on the MISO line.

4️⃣ The MCU calculates the physical value (°C, V, Ω, etc.) according to the associated sensor.

Practical advantage

Advantage	Description
🧩 8 independent entries	Ideal for multichannel systems
⚙️ Universal SPI Compatibility	Works with most microcontrollers
🎯 Good accuracy for a low cost	12 bits → 0.025% of full scale
💡 Very low consumption	<1 mW typical
🧠 Easy integration with RTD, NTC, or amplified thermocouples	Direct conversion after linearization
🔧 No calibration necessary	Ready to use as soon as powered on