Vrefn maximum

[vaque]

Hi all;

I need to know the minimum value of Vrefn. I suppose that according with the manual ((Vrefp-Vrefn)/2) + Vrefn = Vdd/2. Therefore Vrefnmaximum = Vdd - Vrefminimum.

If Vdd=3.3v and Vrefminimum is 2.4v (acording with the manual).

Is Vrefnmaximum 0.9v and then is the maximum sensibility 0.366 mV?

Thanks so much and regards. Daniel.

[vaque]

Yes, I am using a LPC824.

Regards. Daniel.

[soledad]

Hi,

Yes, Vrefn max= 0.9v however

1 LSB = (Vrefp - Vss)/4096 according with the datasheet

Have a great day,
Sol

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[vaque]

Hi Soledad;

LPC82x.pdf Fig 39 image does not indicates a conection between Vrefn and Vss?

I don't understand... Vrefn does not fix the minimum value of the full scale (FS)?

I thought that result of a conversion is:

*A parenthesis between (Vinn-Vrefn) is mising)

But in UM10800.pdf at page 322 "Perform a single ADC conversion using a software trigger"  it says that The result of the conversion is (4095 x VIN)/(VREFP - VREFN).

On one hand this would mean that there isn't an Vrefn offset and on the other hand this would mean that LSB (minimum)[v] ocurrs when Vrefp(minimum) and Vrefn(maximum):

I need more information about the problem please.

Regards. Daniel.

[soledad]

Hello Daniel,

Could you please mention the device you are using?

Regards

Sol