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Question: Is it possible to create a Voltage Controlled Oscillator in PSoC3 / PSoC5 using the PSoC3/PSoC5 hardware?Answer: Yes.  With a handful of hardware components, it is possible to create a voltage controlled oscillator in PSoC3 / PSoC5.  The schematic of a voltage controlled oscillator is shown below.

Question: How do I bring out the VDAC8 output in PSoC 3?  Can I connect the VDAC8 output directly to a pin?Answer: VDAC8 in PSoC3 is implemented by using and IDAC and an internal Load resistance of 16K for 4V range and 4K for 1V range.  Following is the block diagram.

Question: How do I create a High Resolution DAC in PSoC 3?Answer: A High Resolution DAC in PSoC3 may be created by using Dithering.Dithering is a widely used technique in Digital Processing where a noise is intentionally introduced into a system to increase the resolution of the system.  Say we have an 8 bit DAC with a full scale value of 255mV.  Each count of the DAC represents 1mV.  What if we wanted an output of 1.25mV from the DAC.  Switch the DAC output between 1mv and 2mV keeping the output at 2mV 25% of the time and 1mV 75% of the time, the average value of the output would be 1.25mV.  For an output of 1.5mV, the DAC output should be maintained at 2mV for 50% of the time and 1mV 50% of the time.  See diagram below.

Question: How do I create a DAC with resolution greater than 8 bits in PSoC3?  PSoC3 only has 8 bit IDAC and VDAC.Answer: A higher resolution current DAC may be created in PSoC3 by combining two 8 bit DACs.  This is explained in the Technical Reference Manual under the DAC section.  The figure below from the PSoC 3 TRM shows how to combine two 8 bit DACs to implement a 12 bit DAC.