MCP41010: An easy to use digital Potentiometer. If you need to digitally control a resistance this is the chip to use. Use it to make programmable gain amplifiers or create voltage references.

The MCP41010 is a digital potentiometer and allows you to insert a digitally controlled resistance into a circuit.

  • Although digitally controlled, it is a true potentiometer.
  • Can be used as either a potentiometer or variable resistance.
  • Can be used to create Programmable Gain Opamp Amplifiers.
The MCP41010 is not the same as the MCP4725 although they can both output a programmable reference voltage.

Whereas the MCP4725 splits the supply voltage for an output, this chip provides a real potentiometer having has three analogue connections (the same as a potentiometer). The middle is the wiper, labelled PW0, and the other ends of the divider are labelled PA0 and PB0.

It means you can set up the MCP41010 as a controlled resistance or a voltage divider at any point in your circuit.

MCP41010 Specification

Parameter
Value
Voltage Supply (Vs)
2V7 ~ 5V5
Abs Max Voltage
-0V6 ~ 8V0
Bandwidth (load 30pF) 1MHz [1]
Nominal resistance 10k ± 2k
Interface
SPI
Interface Speed
10MHz
Number of bits / positions
8bit/256
DNL (typ), (max)
±1/4, ±1 LSB
INL (typ), (max)
±1/4, ±1 LSB
Full scale error (typ) (max) -0.7, -2 LSB
Zero scale error (typ) (max) 0.7, 2 LSB
Tsettle (Ts typ)
2us [2]
Tempco (typ)
800ppm/ºC
Supply Current (idle): 1uA
Active Current 340, 500uA
Wiper current
±1mA
Operating temperature
-40°C ~ 85°C [3]
[1] For the 50kOhm Version BW is 280kHz, for the 100kOhm it is 145kHz.
[2] For the 50kOhm Version Ts is 8us, for the 100kOhm it is 18us.
[3] Has different part for operating to 125°C.

MCP41010: Block Diagram

MCP41010 Block Diagram

MCP41010: Datasheet

Download the MCP41xxx-42xxx datasheet here.

MCP41010: Pinout

MCP41010 pinout
The same pinout is used for both PDIP and SOIC packages.

MCP41010: Digitally Controlled Potentiometer

mcp41010 as a potentiometer

MCP41010: Digitally Controlled Resistance

mcp41010 as a resistance

In this mode you can set the resistance to near zero Ohms
(52Ohms) with the wiper at position B, using code 00.

Warning: For Code zero (zero resistance), ensure the current is smaller than 1mA to avoid damage.

When the wiper is at position A the resistance will be 9985.94Ohms.

The resolution is : 10e3/pow(2,8) = 39.0625

Max value is (10e3/pow(2,8)) * 255) = 9960.9375

The above figures assume a 10k total resistance which may not be the case (see the specification table) - it can vary between devices.

MCP41010: Single Supply Application circuits

PGA Inverting Opamp

Programmable Gain Inverting Opamp

PGA Non-Inverting Opamp

Programmable Gain Non-Inverting Opamp

PGA Differential Opamp

Programmable GainDifferential Opamp
For this configuration use the dual device MCP42010 to keep the resistor match within the chip. Also use only the same code in each POT for the differential action to work.

Programmable Voltage reference

This provides a similar action to the MCP4275 but with less resolution although you can change the step size with R1 and R2.

Programmable Voltage reference

Use R1 and R2 to increase or decrease the voltage step size.

MCP41010 SPI Control

The following diagrams show you how to control the MCP41010 - as you can see it is very simple. Just output data with 16 clock cycles.

MCP41010 timing

The control bits are as follows:

MCp41010 SPI control bits

Example sketch for Arduino

The SPI interface for the MCP41010 is very simple and you really don't need a library to get the data into the chip. All you do is hold the chip select low, set 16 clocks with data.


#include <SPI.h>

// Pins for SPI comms
#define DATA  11      // SPI Data pin number
#define CLK   13      // SPI Clock pin number
#define CS_DIGIPOT 9  // MCP41010 chip select - digital potentiometer.

void write_digipot(int val) {

   //  // take the CS pin low to select the chip:
  digitalWrite(CS_DIGIPOT,LOW);
  //  send in the address and value via SPI:
  SPI.transfer(B00010001);
  // write out the value
  SPI.transfer(val);
  // take the CS pin high to de-select the chip:
  digitalWrite(CS_DIGIPOT,HIGH);
  SPI.endTransaction();
}

void setup() {
   pinMode(CS_DIGIPOT,OUTPUT);

   SPI.begin(); // Set pins as outputs for SPI hardware.

   write_digipot(128); // Set MCP41010 to mid point.
}

void loop(void) {

}


[File:test_mcp41010]

Conclusions

The MCP41010 is a true digital potentiometer and you can use it as if it were a real physical potentiometer. It has a bandwidth of 1MHz into a 30pF load. The only real limitation is it has reduced current capability so keep the current below 1mA - in practice this allows operation of most circuits very well.

Note: You can find an example using this chip on the AD9833 board.
You may also be interested in the MCP4725 which is a DAC voltage output device that has a high precision (12bit) and is capable of more output current (15mA). It is however not a resistance or potentiometer - it is a precision voltage output device.



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