DALLAS Semiconductor, represented in Australia by Arrow Electronics , has released the DS3906, a triple-variable resistor for low resistance, small step-size applications. Its three 64-step, digital, nonvolatile variable resistors are capable of ohm and sub-ohm step sizes when used in parallel with a fixed external resistor.
All three resistors have 64 positions (plus a high-Z state) with a pseudo-log response chosen to have a linear equivalent resistance when paired with an external resistor. Two of the variable resistors have a range of 66Ω to 101Ω with approximately 0.5Ω step sizes (when used with a 105Ω external resistor), while the third variable resistor has a range of 187Ω to 255Ω with approximately 1Ω step sizes (when used with a 310Ω external resistor).
The DS3906 is suitable for applications requiring calibration. Unlike mechanical potentiometers it enables manufacturers to optimise production by automating calibration while also improving the quality and reliability of their product.
The DS3906 contains 16 bytes of user EEPROM that, like the resistors, are controlled through an I(2)C-compatible serial interface. Three address pins allow up to eight DS3906s to be placed on this same I(2)C bus.
The DS3906 can be factory configured to provide a variety of transfer functions depending on user requirements. It is available in a 3mm x 5mm, 10-pin microSOP and operates from a +2.4V to +5.5V power supply over a -40°C to +85°C range.