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Design >> Mixed-Signal Design >> 8 bit SAR ADC DAC capacitive array!
https://designers-guide.org/forum/YaBB.pl?num=1353148118

Message started by Flynn Rider on Nov 17^th, 2012, 2:28am

Title: 8 bit SAR ADC DAC capacitive array!
Post by Flynn Rider on Nov 17^th, 2012, 2:28am

Dear readers!

I am designing SAR ADC for the first time and have a little problem in designing binary weighted capacitive array for the DAC. I am using a unit capacitance of 8fF. My input signal voltage range varies from 0 to 1V but my capacitive array only covers signals upto 600mV. I have tried changing the ref voltage and the value of capacitors but to no avail. I have attached a figure which shows each bit setting to high value in an 8 bit ADC. When all bits are set the amplitude I am getting is 0.6V. What is that I am missing!

Title: Re: 8 bit SAR ADC DAC capacitive array!
Post by loose-electron on Nov 19^th, 2012, 8:36pm

Capacitance sounds a bit small - May be losing some signal due to
parasitic capacitance.

can you post a schematic of the circuit you are using?