The PSoC can send via I2C 16-bit data, but you will not find a 16-bit DAC in the PSoC world.
Of course you can get I2C external 16 bit DACs, or you could use PSOC 3/5,
16 bit PWM, to build a DAC. Its inherently montonic, requires a LP filter, usually
simple RC. Filter BW trades off settling time for ripple. Generally speaking this
approach is slower than a ladder DAC, but if you do not need speed its a great
way of getting hi res DAC.
If you need absolute accuracy run the PWM out thru a pin whose reference is
a known accurate value, or derive Vdd from a reference.
Attached an ap note on design considerations.
This approach cannot be used for audio. Or fast motor control.
TI PWM DAC.pdf 2.8 MB