How to read VREF ?

Tip / Sign in to post questions, reply, level up, and achieve exciting badges. Know more

cross mob
urchc_1533771
Level 5
Level 5
5 likes given First like received First like given

In 002-02521_CYBLE-012011-00_CYBLE-012012-10_EZ-BLE_PROC_MODULE.pdf page 9  I see that module have pin 10 connected to VREF ( optional input). How can I read voltage on this pin ?

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

Hi Uri,

As I said in my first reply "The Vref pin supposed to give external Vref or connect the bypass capacitor. ". If you could provide an opamp buffer you may use the pin without affecting the normal functioning of the reference generator.

Best Regards,
VSRS

View solution in original post

0 Likes
9 Replies
Vasanth
Moderator
Moderator
Moderator
250 sign-ins 500 solutions authored First question asked

Hello Uri,

The Vref pin supposed to give external Vref or connect the bypass capacitor. You may connect a buffer this and voltage( using an opamp follower), otherwise it may get loaded. The SAR adc uses this as the reference, so measuring this voltage again using SAR ADC doesn't make any sense. If it is just for testing, you can buffer and use the output.

Best Regards,
VSRS

0 Likes

I want to check  power voltage by this pin. Can you explain what  you mean "connect a buffer" ?

I have PROC module without UDBs.

0 Likes
Vasanth
Moderator
Moderator
Moderator
250 sign-ins 500 solutions authored First question asked

You can take the Vref ouput through an opamp in follower mode. You have to route the voltage externally to opamp input pin, and you can use it for your application at output side. This will not load your Vref source.

0 Likes

FYI: In PROC not exist opamps ...

PSoC4vsPRoC.png

0 Likes
Vasanth
Moderator
Moderator
Moderator
250 sign-ins 500 solutions authored First question asked

Hi Uri,

You have to use an external opamp for PRoC devices. You should not directly connect the Vref pin for your application as it is a weak bandgap reference.

Best Regards,
VSRS

0 Likes

External components is not option. I can read voltage without it just using other pin.

I just wondering that exist input pin but I can`t read it. What a reason to waste pin ?

0 Likes
Vasanth
Moderator
Moderator
Moderator
250 sign-ins 500 solutions authored First question asked

Hi Uri,

As I said in my first reply "The Vref pin supposed to give external Vref or connect the bypass capacitor. ". If you could provide an opamp buffer you may use the pin without affecting the normal functioning of the reference generator.

Best Regards,
VSRS

0 Likes

I asked "How to READ this pin" but you answer  "How to use this pin".  I know that I can USE it by setting in ADC but if I selected option in ADC to internal voltage (VDD) this pin is not used.

0 Likes
Vasanth
Moderator
Moderator
Moderator
250 sign-ins 500 solutions authored First question asked

Hi Uri,

Your question was not clear. I understood that you want to read the voltage on this pin from your question, and I have answered that. From your previous response I am guessing you want to use that Vref pin when ADC is not used to read voltage. It is not possible. VREF is a pin dedicated only for that purpose. Please check the datasheet Digital and Analog Capabilities and Connections section if you want to confirm my answer.

Best Regards,
VSRS

0 Likes