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PSoC™ Creator & Designer Forum Discussions

ETRO_SSN583
Level 9
Level 9
100 sign-ins 5 likes given 1000 replies posted

In the module datasheets you have the following issues -

   

 

   

1) Analog mux, you give a selttling time with out any attached resolution. There

   

should be a table of times vs resolution to 20 bits, down to 8 bits.

   

 

   

2) S/H, same problem, you only spec to 1% which is ~ 7 bits, not really a useable

   

number for worst case design. Again a table from 8 to 20 bits.

   

 

   

3) You should show in applicable datasheets how to calc settling time to worst

   

case for a first order R-C network so users can calc their own design. Calc to 1/2 LSB.

   

 

   

Regards, Dana.

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5 Replies
RobynW
Employee
Employee
First comment on blog 10 likes received 50 sign-ins

I've reported the issues to our team.  Thanks for letting us know. -Robyn

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Anonymous
Not applicable

Hi danaaknight,

   

 

   

Could you please specify what device and component you are referring to?

   

 

   

regards

   

Nazar

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HeLi_263931
Level 8
Level 8
100 likes received 50 likes received 25 likes received

@Nazr: Dana already gave a list of affected components (Sample&Hold, AnalogMux). I guess it affects all devices where these components are available.

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ETRO_SSN583
Level 9
Level 9
100 sign-ins 5 likes given 1000 replies posted

Anything in analog signal path that is band limited. I would add OpAmps,

   

Mixer to the list. The whole conecpt of having a 20 bit A/D, or 12 bit SAR for that

   

matter, only works right when one does not incur settling time violations

   

performing measurements resulting in measurement error.

   

 

   

Regards, Dana.

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ETRO_SSN583
Level 9
Level 9
100 sign-ins 5 likes given 1000 replies posted

Not to be forgotten would be worst case drift, PSRR effects. Even GBW in OpAmps

   

contribute to AC measurement errors.

   

 

   

I think a spreadsheet of all potential errors associated with a component should be

   

created and one by one either specifications be entered or notes guarenteed by

   

characterization.

   

 

   

The reason we buy test instrumentation from Agilent and Tek and Keithley and Marconi

   

and....is they have done all this worst case analysis in their designs to back up their specs.

   

Otherwise their competitors would quickly point out their 8.5 digit DVM is really only a

   

4 1/2 digit and destroy their customer base confidence.

   

 

   

Regards, Dana.

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