MCP4011T-103E/SN Digital Potentiometer: Key Features and Application Circuit Design
The MCP4011T-103E/SN from Microchip Technology is a compact, single-channel, 7-bit (128 wiper steps) digital potentiometer designed to replace traditional mechanical potentiometers in a wide array of electronic circuits. This device offers a non-volatile memory, which is a critical feature, as it allows the wiper position to be retained even after power is removed and then restored. This makes it ideal for applications requiring a preset configuration upon startup without manual recalibration.
Housed in a space-saving 8-pin SOIC package, the MCP4011T-103E/SN provides a total end-to-end resistance of 10 kΩ. It operates on a single power supply voltage ranging from 2.7V to 5.5V, making it perfectly suited for both 3.3V and 5V systems. Communication with a microcontroller is straightforward via a simple 3-wire SPI-compatible (Up/Down) interface, minimizing the number of required I/O pins and simplifying the control software.
Key Features:
7-Bit Resolution: 128 discrete wiper positions.
Non-Volatile Wiper Storage: Retains the last wiper position during power-off.
Low Power Consumption: Ideal for battery-powered portable devices.
Simple Up/Down Interface: Easy digital control without a complex protocol.
Wide Operating Voltage: From 2.7V to 5.5V.
Application Circuit Design: Programmable Gain Amplifier (PGA)
A common and practical application for the MCP4011T-103E/SN is in designing a programmable gain amplifier for analog signal conditioning. This circuit allows software-controlled adjustment of an amplifier's gain.
Circuit Configuration:
1. Core Components: An operational amplifier (op-amp) configured in a non-inverting topology and the MCP4011T-103E/SN digital potentiometer.
2. Connections: The digital pot is used in the rheostat mode (using only the wiper and one terminal). It is connected in series with a fixed resistor (`R_fixed`) between the output and the inverting input of the op-amp.
3. Operation: The total resistance in the feedback path (`R_feedback = R_wiper + R_fixed`) determines the gain of the amplifier along with another resistor to ground (`R_gnd`). The gain formula for the non-inverting amplifier is approximately `Gain = 1 + (R_feedback / R_gnd)`. By digitally controlling the wiper position of the MCP4011T-103E/SN, the value of `R_feedback` is changed, thereby programmatically adjusting the amplifier's gain.
4. Microcontroller Interface: A microcontroller uses three digital I/O pins (to control the CS, U/D, and INC pins of the potentiometer) to send pulses and change the resistance value.
This design eliminates the need for a physical adjustment, enabling remote control, automation, and self-calibration features in systems such as audio equipment, sensor interfaces, and automated test equipment.
ICGOODFIND: The MCP4011T-103E/SN stands out for its excellent combination of non-volatile memory, a simple digital interface, and compact packaging. It is a highly effective solution for replacing mechanical trimmers, enabling design miniaturization, enhancing reliability by removing moving parts, and adding intelligent, software-controlled adjustment capabilities to both new and existing designs.
Keywords: Digital Potentiometer, Non-Volatile Memory, SPI Interface, Programmable Gain Amplifier, Signal Conditioning.
