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ADAU1701 Full Scale Output Voltage Slightly Low for Full Scale Input Voltage

Question asked by Jesse4801 on Apr 25, 2018
Latest reply on Apr 30, 2018 by Jesse4801

Hi,

 

I am using the ADAU1701 DSP and I am passing a full scale input signal (2V RMS) directly through from the external 18k resistor on ADC0 (Pin2) to VOUT0 (Pin46). The issue is that I am finding that the output voltage is 35mV short of 0.9V RMS full scale output of the DAC.

 

The signal level detector is showing -4dB. If I put in an input signal slightly greater than 2V RMS, the signal meter will go to -3dB etc (see attached screenshot).

 

I've double checked the hardware. I am sampling at 48kHz. therefore ADC0 and ADC_RES are fitted with an 18k external resistor (+/-1% tolerance) as per the datasheet (see attached schematic snippet).

I’ve also double checked that I am initializing the DAC Setup Register as per page 44 of the datasheet.

 

That datasheet doesn't specify a tolerance on the full-scale output of the DAC but just states 0.9V RMS as the typical.

 

Just wondering if the 35mV error that I am getting is within tolerance of the chip or if it is large enough to warrant further investigation of my design?

 

Kind Regards,

 

Jesse

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