7-bit I²C current DAC — two channels, one supply rail
The DS4422N+T&R: The I²C data interface keeps the pin count low — the 14-TDFN package (3×3 mm) routes the two DAC outputs, the bus lines, and the supply pins, leaving the rest of the board for the analog front end.
Current sink/source architecture and linearity budget
The unbuffered current output can be configured as either a sink or a source — the same pin pulls current to ground or pushes it into the load, which simplifies the BOM when the same DAC must drive both NPN and PNP bias stages. Integral nonlinearity is ±1 LSB max, differential nonlinearity ±0.5 LSB max — the monotonicity guarantee across the 128 codes means the output never steps backward, critical when the DAC sets a threshold in a comparator or a regulator feedback divider. The 7-bit resolution (128 steps) is coarse compared to a 12-bit DAC, but the current-mode output eliminates the external op-amp needed for a voltage-output DAC driving a current loop — the trade-off is resolution for simplicity.