Digital Potentiometer Questions - MCP41010, MCP454x/6x, MCP464x/6x - Make Before Break, Audio Applications

Does the MCP41010 feature 'make before break' when changing the wiper position?

No. Most digital potentiometers do NOT implement either a make before break or break before make functionality.

Both implementations have issues. For example, in a make before break implementation, if the wiper code goes from Zero-Scale to Full-Scale, then the RAB value is temporarily shorted by both wiper resistors being turned on (make) and the IAB would spike (VAB / (2 * RW) vs. VAB / RAB). This type of implementation is only recommended where code change range is limited, e.g., for devices that have an increment or decrement interface. Our increment/decrement devices do not implement make before break.

Does Microchip have app notes regarding digital potentiometers in audio applications?

No, but, due to continuous improvements implemented in our datasheets, the MCP454x/6x - MCP464x/6x Datasheet has information that are useful in audio applications.

In section 4.2.1, Figure 4 lists the gain as: Vout = -Vin * (Rb/Ra) + Vref * (1 + Rb/Ra). I am confused by the second term on the right of the equals sign. Traditional inverting op-amps show the gain as -Vin * (Rb/Ra). Is the equation in Figure 4-4 valid?

The equation in Figure 4-4 is correct. This section Vref * (1 + Rb/Ra) is a result of the positive input being tied to Vref rather than GND.

For additional information, please read application notes AN1316 and AN1080.

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