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ADuCM360 ADC calibration using AVDD as reference

Question asked by Aladdin on Mar 14, 2013
Latest reply on Mar 20, 2013 by MMA

Hello everyone

 

I am using ADuCM 360 with its 2 ADC converters. The AVDD is used as reference voltage for the ADCs and gain of 1. The readings of the ADCs contains a slight error of 20 mV. It is stated in the data sheet a calibration is needed when AVDD is used as a reference to update ADCxVDDGN. I did the calibration in the initialization of the ADC as follow

 

AdcMski(pADI_ADC0,ADCMSKI_RDY,1);              // Enable ADC0 ready interrupt source 

AdcFlt(pADI_ADC0,157,8,FLT_NORMAL|ADCFLT_NOTCH2|ADCFLT_RAVG2); // ADC filter set for 4.5Hz update rate

AdcRng(pADI_ADC0,ADCCON_ADCREF_AVDDREF,ADCMDE_PGA_G1,ADCCON_ADCCODE_INT); // VDD reference selected, Gain of 1, Signed integer output

AdcGo(pADI_ADC0,ADCMDE_ADCMD_IDLE);       // Place ADC0 in Idle mode

AdcGo(pADI_ADC0,ADCMDE_ADCMD_INTOCAL); // Internal zero offset calibration

AdcGo(pADI_ADC0,ADCMDE_ADCMD_IDLE);

AdcGo(pADI_ADC0,ADCMDE_ADCMD_INTGCAL);  // Internal full scale gain calibration to update ADC0VDDGN

AdcGo(pADI_ADC0,ADCMDE_ADCMD_IDLE);

 

but still the output readings of the ADC are not accurate. please can any one help me, is this calibration steps are correct? 

 

Many thanks in advance

 

Aladdin

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