LPC5528 ADC input

[yuto]

 

Hi.

I have a question about the connection of the ADC input pins of the LPC5528.
As shown in the attached circuit, I want to measure a voltage greater than the power supply of the LPC5528 with the ADC.
Therefore, the input voltage is lowered by resistor voltage divider, do I need to consider the RADIN described in AN13033?
(Can you read with 2.48V and an ADC, as in the attached circuit?)

[gusarambula · Accepted solution]

Hello Yuto,

Having a voltage divider as to reduce the ADC voltage to fit the allowed range is a valid (and often used) alternative.

You would need to consider the ADC input resistance on your design. I would recommend looking at Application Note 4373 for more details on how to ensure good measurements. They do not cover voltage dividers on the input, but the overall principles will be of help. Just consider that the naming convention of this application note uses Rsh instead of Radin for the input resistance.

https://www.nxp.com/docs/en/application-note/AN4373.pdf

I hope that this information helps!

Regards,
Gustavo

[yuto]

Thank you, Gustavo, for your reply!

I found that you have to take into account the ADC input resistance.
I will refer to the document.