2 Replies Latest reply on Dec 14, 2013 5:58 PM by user_14586677

+/- (6*Vref) in Delata Sigma ADC

The range of the ADC will be (Negative Input)+/-(x*Vref).(x can be 1/2, 1/4, 1/8, 1/16, 1, 2 or 6)

The Vref can vary between 0.9 to 1.3V. Because external reference can also be used.

If we use the (Negative Input)+/-(2*Vref), and the reference voltage is 1V. Then the ADC range will be (Negative Input)+/-2V. So if I fix the negative input at 2V, I can get digital readings between 0-4V (2-2=0,2+2=4).

So If I need to measure from 0-5V its not possible.

But if I go with the next range,(Negative Input)+/-(6*Vref), I can cover the full voltage swing.

So if the Vref used is 0.9, the range will be   (Negative Input)+/-5.4V.

If the Vref used is 1.2V, then the range will be  (Negative Input)+/-7.2V.

You can fix the negative input at any voltage to get full swing.

But the limitation is the Pin voltage and current levels.

This has to be taken care. The pin voltage should not exceed 5.5V.

And negative voltage should not be given to a PSoC pin.

So to measure the negative voltages, kindly go through the below blog,

http://www.cypress.com/?rID=50815&cache=0

Keerthi
• 1. Re: +/- (6*Vref) in Delata Sigma ADC

Vdda ranges from -.5V to +6V. The max pin voltage range for

analog is Vssa<< Vpin << Vdda or 6V >= Vpin >= -.5 V

The CM range for the DelSig, buffer bypassed, is 100 mV outside

the rails, eg.    Vdda + 100 mV >= Vin >= Vssa - 100 mV

PSOC datasheet, Document Number: 001-11729 Rev. *Z  Revised September 10, 2013

Regards, Dana.

• 2. Re: +/- (6*Vref) in Delata Sigma ADC

To measure voltages outside the DelSig CM range, specifically

negative voltages, see attached possibilities.

Regards, Dana.