Digital Potentiometers
Microchip’s family of digital potentiometers offer a wide range of options. These devices support 6-bit through 8-bit applications, offering volatile and non-volatile options with digital interfaces, from a simple up/down interface to the standard Serial Peripheral Interface (SPI) and I²C interfaces. These devices are available in small packages, such as 6-lead SC70 and 8-lead Dual Flat No Leads (DFN) for single potentiometer devices, 14-lead Think Shrink Small Outline (TSSOP), and 16-lead Quad Flat No Leads (QFN) packages for dual potentiometer devices, and 20-lead TSSOP and QFN packages for quad potentiometer devices. Non-volatile devices offer a Wiperlock™ Technology feature. Volatile devices operate down to 1.8V. Resistances are offered from 2.1 kΩ to 100 kΩ. Over 50 device configurations are currently available.
Microchip’s Family of Digital Potentiometers
Microchip offers a range of devices that allow you to select a device that is the best fit for your application. Some of the selection options include:
- A wide range of resistor values
- RAB resistance (typical) from 2.1 kΩ to 100 kΩ
- Step resolution
- 6-bit
- 7-bit
- 8-bit
- Serial interfaces
- Up/down
- SPI
- I²C
- Memory types
- Volatile
- Non-volatile
- Resistor network configurations
- Potentiometer (resistor divider)
- Rheostat (variable resistor)
- Single, dual, and quad potentiometer options
- Package options
- Special features
- Shutdown mode
- WiperLock technology
- Low voltage, Low power options
Resistor sizes and resolutions allow you to select the step resistance and the number of steps. For the device with resistance (RAB) equal to 2.1 kΩ, there are 64 steps (63 resistors), so the step resistance (RS) equals RAB/63 (or 33.33 Ω). For a 5 kΩ device with 257 steps (256 resistors), a step resistance (RS) equals RAB/256 = 19.53 Ω. At the other end of the spectrum, for the device with the resistance (RAB) equal to 50 kΩ, there are 64 steps (63 resistors), so the step resistance (RS) equals RAB/63 (or 793.65 Ω).
The serial interface options allow you to easily integrate the device into the application. For some applications, the simple up/down interface will be adequate. For devices with higher resolution (7-bit, 8-bit) being able to directly write/read the wiper register is desirable. This is supported with SPI and I²C interfaces. SPI is simpler to implement, but I²C uses only two signals (pins) and supports multiple devices on the serial bus without additional pins. The availability of both volatile and non-volatile devices allows the designer flexibility in optimizing the application. Some applications may use the digital potentiometer as a replacement for a mechanical potentiometer. In this case, a non-volatile device with the serial interface connecting to the test hardware interface allows a low-cost device with low-cost manufacturing. Resistor network configurations allow the package size/ cost to be minimized for the desired functionality. If a variable resistor (rheostat) with one terminal tied to ground is desired, then only one resistor terminal (the wiper) needs to be implemented. In the MCP4017/18/19 family, this configuration is shown in the MCP4019 and allows this functionality to be achieved in a low-cost SC70-5 package. Dual and quad digital potentiometer resistor networks are closely matched since they reside on the same silicon. Matched components allow you to achieve better system performance in some applications. Packaging options allow you to address your system requirement trade-offs including device cost, board area, and manufacturing sites (surface mount vs. thru-hole). Packages include 3x3 mm SOT-23 and DFN packages, 3x2 mm DFN package and tiny SC70 packages.