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Resolution AFE MKM34Z256

Question asked by ioi labs on Jul 24, 2018

Hey,

 

I want to understand what is the exact resolution of the AFE. I use TWR-KM34Z75M. For my minds, as I use Adc 24 bits resolution is : quantum = Vref/(2**n-1) with Vref = 1.2V et n=24.

 

In Sdk example "afe_interrupt", on Vref initialization function VrefH (1.2V ) and VrefL (0.4V) are initialized. Why VrefL is it needed ? Exact tension resolution is it Vref = VrefH - VrefL = 0.8V ?

void APP_VREF_Config(void)
{
    vref_config_t config;

    /* Get vref default configure */
    /*
     * config.bufferMode = kVREF_ModeHighPowerBuffer;
     * config.bufferMode = kVREF_ModeTightRegulationBuffer;
     * config.enableExternalVoltRef = false;
     * config.enableLowRef = false;
     */
    VREF_GetDefaultConfig(&config);
    /* Enable low reference volt */
    config.enableLowRef = true;


    /* Init vref */
    VREF_Init(VREF, &config);


    /* Vref set trim reference */
    VREF_SetLowReferenceTrimVal(VREF, 3U);


    /* Vref set trim, this value will not be the same with every boards */
    VREF_SetTrimVal(VREF, DEMO_AFE_VREF_TRIM);
}

 

 

Can you give me exact way to convert Adc value to real value please ?

 

Thanks for advance,

IOI Labs

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