Questions about ADC

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Anonymous
Not applicable

Hello everyone!  I am developing a board where I would be using a PSOC target chip ONLY to measure  voltages ranging from 0-5V.

I have the following questions:

1. How can I flash firmware onto the Target chip without the KitProg present on my board?

2. What does internally/externally regulated mode mean?

3. I am highly confused about the Vref for the SAR ADC. Datasheet suggests that if I choose the  input range to "Vssa to Vdda Single Ended" and Reference to "External", my Vref is capped at 2.5V.

How does that work? Does the Vref get doubled internally;otherwise how can I measure voltages from Vssa to Vdda Single Ended?  

To be explicit, I need 5V reference because I need to measure voltages upto 5V. Do let me know if I am  making an error somewhere. Thanks!

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1 Solution
Vasanth
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250 sign-ins 500 solutions authored First question asked

Hi Abhishek,

Q1. How can I flash firmware onto the Target chip without the KitProg present on my board?

There are multiple methods.

Q2. What does internally/externally regulated mode mean?

PSoC has the flexibility to use the internal regulator or external regulator for the device. Please see power system section in the following application note. http://www.cypress.com/file/44581/download

Q3. I am highly confused about the Vref for the SAR ADC. Datasheet suggests that if I choose the  input range to "Vssa to Vdda Single Ended" and Reference to "External", my Vref is capped at 2.5V. How does that work? Does the Vref get doubled internally;otherwise how can I measure voltages from Vssa to Vdda Single Ended? 

This due to the differential architecture of the SAR ADC. The component just avoids any confusion while selecting the reference by giving you an option to select the range you want to work on, and the rest of the configuration will be taken care by the component.

I hope this answers your question.

Best Regards,

VRS

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3 Replies
Vasanth
Moderator
Moderator
Moderator
250 sign-ins 500 solutions authored First question asked

Hi Abhishek,

Q1. How can I flash firmware onto the Target chip without the KitProg present on my board?

There are multiple methods.

Q2. What does internally/externally regulated mode mean?

PSoC has the flexibility to use the internal regulator or external regulator for the device. Please see power system section in the following application note. http://www.cypress.com/file/44581/download

Q3. I am highly confused about the Vref for the SAR ADC. Datasheet suggests that if I choose the  input range to "Vssa to Vdda Single Ended" and Reference to "External", my Vref is capped at 2.5V. How does that work? Does the Vref get doubled internally;otherwise how can I measure voltages from Vssa to Vdda Single Ended? 

This due to the differential architecture of the SAR ADC. The component just avoids any confusion while selecting the reference by giving you an option to select the range you want to work on, and the rest of the configuration will be taken care by the component.

I hope this answers your question.

Best Regards,

VRS

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Anonymous
Not applicable

Hey VRS,

Thank you very much for replying with detailed resources.

I am fairly certain that my doubts about the first and second question have been cleared. However, just to get an explicit answer for the third question : While trying to measure voltages using SAR ADC, I can either use Internal or External Vref (both capped at 2.5V) and I can measure voltages in the 0-5V range?

Apologies for pestering. Thanks.

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Vasanth
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250 sign-ins 500 solutions authored First question asked

Hi Abhishek,

The internal reference is 1.024V. In that case the range will be 0 to 2.048 in single ended mode. You can use a VDAC for this purpose, and set it to 2.5 V for 0-5V range output. The simplest solution will be selecting VSSA to VDDA option in the component. Please see the attached image.

pastedImage_0.png

Best Regards,
VRS

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