topic Re: LPC54608 ADC locks in LPC Microcontrollers

LPC54608 ADC locks

F_Vaquero — Mon, 19 Jul 2021 21:08:00 GMT

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?

Re: LPC54608 ADC locks

Omar_Anguiano — Thu, 22 Jul 2021 23:01:43 GMT

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

Re: LPC54608 ADC locks

F_Vaquero — Fri, 23 Jul 2021 16:34:35 GMT

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,