100 taps, 100 kΩ, linear — the trim pot for production calibration
The Maxim Integrated DS1804U-100+T&R is a single-channel, non-volatile digital potentiometer with 100 tap positions and a linear taper over a 100 kΩ end-to-end resistance. It stores the wiper setting in non-volatile memory, so the calibration holds through a power cycle without a microcontroller intervention or external EEPROM. The three-wire Up/Down interface (U/D, INC, CS) is straightforward for a firmware engineer to drive from any GPIO bank — no SPI or I²C bus required, which saves pins on a small MCU. The 2.7 V to 5.5 V supply range covers 3.3 V and 5 V logic rails commonly found in industrial sensor transmitters, programmable power supplies, and audio gain stages.
Wiper resistance and temperature drift — the hidden limits
The wiper resistance is 400 Ω typical, which adds a fixed series offset at the wiper terminal. In a voltage-divider configuration that offset is negligible, but in rheostat mode (wiper to one end) the minimum resistance is 400 Ω, not zero — a detail that matters when setting a low-impedance bias point. The temperature coefficient is 750 ppm/°C typical, so a 100 kΩ setting drifts about 75 Ω per degree. For a room-temperature trim that is fine; for a -40°C to 85°C span the drift can shift the set point by several percent, so budget the tolerance (±20%) plus the tempco in the system error analysis.
Active production, RoHS3, and the 8-uMAX footprint
The 8-uMAX/uSOP package (3.00 mm width, 0.118" pitch) is a common footprint shared with the DS1804-050 and other 8-pin digital pots from Maxim, so a board layout can accommodate multiple resistance values on the same pad pattern. Cut Tape (CT) is also available for prototype quantities.
The DS1804U-050 variant offers 50 kΩ end-to-end resistance with the same tap count and interface, useful when a lower impedance range is needed without changing the PCB layout.