LPC54608 ADC locks

[F_Vaquero]

I'm using the LPC54608 ADC with MCUXpresso and everything is working fine until I test some ESD at the proximity of the board. Sometimes, at the ESD, I see that the converter locks in the while statement that I have to wait until the conversion is done.

I'm working with 180MHz system clock and synchronous ADC clock at 60MHz. This is the code to do the conversion:

uint16_t ad_PointsConversion(void){

    adc_result_info_t adcResultInfoStruct;

    adc_conv_seq_config_t adcConvSeqConfigStruct;

    uint32_t result;

    adcConvSeqConfigStruct.channelMask = (1U);/* Internal temperature sensor channel*/

    adcConvSeqConfigStruct.triggerMask      = 0U;

    adcConvSeqConfigStruct.triggerPolarity  = kADC_TriggerPolarityNegativeEdge;

    adcConvSeqConfigStruct.enableSingleStep = false;

    adcConvSeqConfigStruct.enableSyncBypass = false;

    adcConvSeqConfigStruct.interruptMode    = kADC_InterruptForEachSequence;

    ADC_SetConvSeqAConfig(AD_ADC_BASE, &adcConvSeqConfigStruct);

    ADC_EnableConvSeqA(AD_ADC_BASE, true); /* Enable the conversion sequence A. */

    /* Clear the result register. */

    ADC_GetConvSeqAGlobalConversionResult(AD_ADC_BASE, &adcResultInfoStruct);

    ADC_DoSoftwareTriggerConvSeqA(AD_ADC_BASE);

    while (!ADC_GetConvSeqAGlobalConversionResult(AD_ADC_BASE, &adcResultInfoStruct))

    {

    }

    result = adcResultInfoStruct.result;

    ADC_EnableConvSeqA(AD_ADC_BASE, false); /* Disable the conversion sequence A. */

return result;

}

Sometimes, I can recover the ADC with a new ESD. Is there any reported issue about ADC locking due to noise at VREFP or AVDD? Any idea to avoid this locking?

[Omar_Anguiano · Accepted solution]

Hello

Hope you are well.
I have seen a similar behavior in this case: https://community.nxp.com/t5/LPC-Microcontrollers/LPC54628-ADC-reading-invalid/td-p/1295336
Signals in the pin above the VDDA might be causing the issue you are having. 

I suggest you to have a protection circuit for the pin and the supply voltage. Variations and over-voltage on the supply pin can cause unexpected behaviors of the device.

If you have more questions do not hesitate to ask me.
Best regards,
Omar

[F_Vaquero]

Thank you very much Omar,

Now we have transils at the inputs (to limit a 3V3) but we can try with lower voltage transils since our reference voltage for the ADC is 2V5.

We will add as well more capacitance to inputs, VDDA a VREFP. Specially low value ceramic capacitors to work well at high frequency.

Regards,