Linearity of a DAC0800 Current Output R2R DAC

The DAC0800 is a current output R-2R DAC with 8 bits of resolution. As part of a solar panel monitor, the DAC0800 serves as a programmable reference for a shunt regulator. The output of the DAC is mirror 1:1 into a \(5\;k\Omega\) load; forming the voltage reference for the shunt regulator. A simplified schematic of the DAC is shown below.

Simplified schematic of a DAC0800.

The DAC is swept from code 0 to code 255 and the output of the shunt regulator is recorded. The resulting transfer function of programmable shunt regulator is shown in the figure below.

Transfer function of DAC0800 and LM324 programmable shunt regulator.

The integral non-linearity of the system is determined as the residual form a least-squares fit of a first order function. The plot below depicts the system INL, the magnitude is normalized to LSBs.

DAC0800 INL

A worst case INL of 0.24 LSB is observed at the full-scale code (255).

DNL of the system is measured as the difference from 1LSB at each code step.

 

DAC0800 DNL

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