50kΩ, 256-tap, dual-channel digital pot with non-volatile memory
The MAX5478ETE+ is a dual-channel digital potentiometer from Maxim Integrated, configured as a linear-taper potentiometer with 256 tap positions per channel and a total end-to-end resistance of 50kΩ. Each channel is independently controlled via an I2C interface, and the wiper position is stored in non-volatile memory, so the setting persists across power cycles without a separate EEPROM write sequence.
Temperature drift and wiper resistance — the specs that govern set-point accuracy
The 70ppm/°C temperature coefficient means a 50°C swing shifts the resistance by about 175Ω — roughly 0.35% of full scale — which is acceptable for most bias and adjustment circuits but worth derating if the pot sets a precision reference voltage. Wiper resistance is 325Ω typical, which adds a series offset at the wiper terminal; the effective resistance between wiper and either end of the string is the programmed tap resistance plus this 325Ω, so the minimum output resistance is never zero. Tolerance is ±25% on the total end-to-end resistance — the absolute value varies part-to-part, but the ratiometric tap accuracy (the INL/DNL between adjacent taps) is tighter, so the pot is better suited for divider applications than for precision absolute resistance.
Supply range, interface, and memory type for system integration
The I2C interface supports a selectable address (via the Selectable Address feature), allowing up to two of these devices on the same bus without address conflicts — useful when calibrating multiple channels from one microcontroller. Non-volatile memory stores the wiper setting at power-down and restores it on power-up, so the pot does not need a re-initialization routine after every brown-out or power cycle.
16-TQFN (3x3) exposed-pad package — PCB layout and thermal considerations
Surface-mount assembly with a standard reflow profile is typical; the package is compatible with lead-free solder processes given the ROHS3 compliance.