Oct 12, 2009
By M Ganesh Raaja
PSoC3 has 8 bit voltage and current DACs. Higher resolution DACs may be created by combining two 8 bit DACs, one for MSB and one for LSB and summing their outputs together. The DAC section of the TRM shows how to chain two 8 bit DACs to get a 12 bit DAC.
The MSB is implemented using an 8 bit DAC configured for 2.040mA full scale. Each bit of the MSB DAC now corresponds to 8uA. To create a 12 bit DAC, we need to extend the resolution by four bits and each bit should be equal to 1/16 of the MSB DAC, which is 0.5uA. This can be implemented by using Bits 2 to 5 of another 8 bit DAC configured for a 32uA output. The schematic diagram of a PSoC3 project to create a high resolution current DAC is shown below.
Below is the code that is used to split the 12 bit DAC value and update the MSB and LSB DACs.
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