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We are using LTC2400 interfaced with NXP LPC1768 microcontroller and manually controlling SCK and reading SDO lines.

As mentioned in the datasheet, we are following the sequence as shown below,

CS-> Low

Check SDO pin value,

if == 1, CS=High , Return

else Clock SCK 32 times , read the pin value of SDO 


Remove last 4 bits of SDO data and mask first 4 bits of data , use the remaining 

But the converted data is continously flactuating even when analog input line is connected to ground.

Where are we going wrong?

  • Hi,

    We will look into this, I'll contact the product owner and get back to you.



  • With a 24-bit ADC it is not possible to ever have a stable code from conversion to conversion. Looking at the noise histogram on page 6 of the LTC2400 data sheet, you will see that the output code varies +/-1.2ppm. This is +/-10LSBs. This can only be achieved with a very low noise source. You say you are connecting the input to ground but if you are using a long wire to do this, it will act as an antenna picking up lots of noise.

    Does your PCB have a solid ground plane and do you have the suggested bypass in place with very short leads between pins and ground plane?