topic Re: K82 Kinetics DAC Voltage reference in Kinetis Microcontrollers

K82 Kinetics DAC Voltage reference

mhanuel — Tue, 04 Apr 2017 23:56:38 GMT

Hello All,

Will appreciate anyone that can clarify the following about K82 Voltage Reference for DAC module.

Datasheet page 52 Note 1 says:

"The DAC reference can be selected to be VDDA or VREFH."

But reference manual page 1429 (46.1.3 12-Bit DAC Reference) says:

"For this device VREF_OUT and VDDA are selectable as the DAC reference.
VREF_OUT is connected to the DACREF_1 input and VDDA is connected to the
DACREF_2 input. Use DACx_C0[DACRFS] control bit to select between these two
options."

I need to use a precision 2.5V reference, should I then connect the Reference Output to VDDA? and leave VREFH floating, I cannot see how to select the VREFH for DAC, for ADC there is the SC register.

Thank you in advance,

Re: K82 Kinetics DAC Voltage reference

miduo — Thu, 06 Apr 2017 07:47:30 GMT

Hi,

Please ignore the description of the datasheet. Make the reference manual as a correct that VREF_OUT and VDDA are selectable as the DAC reference.

For your case, an external voltage reference can be used as the DAC voltage reference by connecting it to the VREF_OUT pin and selecting VREF_OUT as the DAC reference.

Re: K82 Kinetics DAC Voltage reference

mhanuel — Thu, 06 Apr 2017 14:23:11 GMT

Hello Fang Li,

Thank you for your answer,

I thought the VREF_OUT pin is an output only, do you mean that I should connect my external reference to this pin?

Since my design only needs DAC and DAC IDDA current is 700uA I was connecting the 2.5V reference to VDDA directly.

Would you please clarify which is the preferred approach?