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which source to use? | Cypress Semiconductor

which source to use?

Summary: 7 Replies, Latest post by PSoC Rocks on 19 Jan 2013 11:18 PM PST
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user_224473785's picture
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19 posts

 i want to connect 2.048V source to the negative input of ADC in the top design layout in Creator 2.1.which source shall i use?VDAC,battery or Vref?

user_14586677's picture
User
7648 posts

Why the offset to ADC ? Are you using + input to ADC from a bridge

element, a little better description of why you need the offset would

help forum assist you.

 

In general, offsetting from a reference would make most sense to

preserve absolute accuracy, if thats what you are seeking.

 

Regards, Dana.

PSoC Rocks's picture
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141 posts

You can use a VDAC for giving offset of 2.048V or a Vref component followed by PGA of gain 2.

user_14586677's picture
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7648 posts

Keep in mind the onboard reference is accurate to +/- .1% and the

PGA gain error is > +/- .15%, its offset error is 10 mV, and its PSRR

is 48 db, so factor those into your error analysis.

 

Regards, Dana.

rahulram's picture
Cypress Employee
115 posts

Using a battery is something that i would suggest, if you are looking for a higher resolution(higher ENOB).

If you are OK with a resolution less than or equal to 16bits, then you can seek the help of references and DACs as the preconditioning circuit always reduces the ENOB.

 

user_14586677's picture
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A battery is not a panacea for fixing a reference problem, as it has

a noise contribution, its noise rises with depletion, and usually one

needs a R network to get the reference voltage of interest which also

contributes to ENOB reduction.

 

Conduct a complete signal chain analysis and that will reveal the issues.

 

Regards, Dana.

PSoC Rocks's picture
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141 posts

Best is to try out all possibilities and select which is suiting your requirements.

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