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AFE0256 questions

Paul Schoenke
Expert 1375 points

Other Parts Discussed in Thread: AFE0256

Hello:

I wasn't sure where to post this question, so I hope this is a good place.  I did not see any E2E posts on this device.

I'm interested in the TI AFE0256 device, but have a few questions:

1-      On the specs sheet it listed noise as 758 e- RMS. If this this is read noise, it is rather large. Could someone please let me know how the noise was measured?

Noise: 758 electronRMS (eRMS) with 28-pF Sensor Capacitor in 1.2-pC Range

 

2-      Was the “minimum scan time” the time that reads one pixel?

Minimum Scan Time: Normal Mode: 37.9us, Internal ADC

Any feedback or input is welcomed and appreciated!

thanks again!

Paul

Thanks,

  • 0
    TI__Prodigy 315 points

    Paul,

    1) The noise the total noise of the channel (which includes the front end, the CDS and the ADC). It is measured as follows: No signal is given to all channels. Ideally one would get only a fixed offset code. But the noise will cause some std dev per channel. The output std deviation in ADC code for a particular channel is measured, say x. This is converted into electrons as follows. Noise in e- = (x/16384)*(Q/1.6e-19). Here Q is the charge range in Coulomb.

    2) Yes. The 0256 can read a given pixel at the rate of 37.9us. Note that it reads 256 pixels during each read.

    Regards,

    Nagesh