Fluctuations in ADC result of LPC54608J512BD208

[prasannanaik]

Hi,

I am using ADC of LPC54608J512BD208 in an application in interrupt mode with interrupt after sequence A is completed. I have 8 channels (ADC0_0, ADC0_4, ADC0_5, ADC0_6, ADC0_7, ADC0_8, ADC0_9, ADC0_10) in the sequence. ADC is operating at 1 Mhz and core clock is 100 Mhz. ADC sampling time is 22 clocks.

During testing with PE micro/LPC11U68 development board as debugger, i found that the fluctuations are around 70 counts as attached in the screenshot whereas if i don't use debugger and send the ADC data on UART, i get fluctuations of less than 10 counts.

What is the reason for this fluctuation?

Thanks & best regards,

Prasanna

[Alice_Yang]

Hello Prasanna,

What about your real signal ? Maybe there is some delay with debugger, then the fluctuation of data is large.

[prasannanaik]

Hi Alice,

Thanks for your reply!

I have check the signal on a DSO and noise was around 4 microvolt.

Also, had there been noise in the hardware it would be reflected in the UART data as well right?

Thanks & best regards,

Prasanna

[Alice_Yang]

yes.