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DAC reference problem

Yefu
Intellectual 365 points
Other Parts Discussed in Thread: DAC5311

It's a general question, not special to any product.

Can I use DC/DC output as DAC reference voltage?

I measure the DC/DC output with  oscilloscope, and find the DC/DC output is not very stable.

  • 0
    TI__Guru**** 180991 points

    Hi Yefu,

    In general terms, the analog output of a DAC or the digital results from an ADC are only as good as the reference they used to perform the conversion.  Depending on the resolution of the DAC in question, your output voltage  will be 'unstable' as well. 

    Let's say for instance you have an 8-bit DAC like the DAC5311, with an output voltage range of 0-Vref and the reference voltage is 5V.  You'd have 255 output levels or steps from the DAC, each representing 19.6mV.  That would be your least significant bit or LSB size.  In an ideal DAC, the transfer function passes through the midpoint of each step giving you an uncertainty of +/- 1/2 LSB  (or 9.8mV) per input code.  So, if your reference is not stable to at least 5V +/-9.8mV, your DAC output voltage will be higher/lower than expected and you loose resolution.