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VREF Source (JP500)
The VREF source jumpers select whether an internal or external voltage reference supplies the VREF0, VREF1 and
VREF2 signal of the processor. This jumper must be installed. This selection also determines the DC Bias of the
input of the ADC. This is midscale of the ADC range (3.0V).
ADC VINx
At the input of each ADC channel there is an RC circuit positioned almost directly at the input pin of each ADC
channel. It consists of a resistor of 33ῼ and a capacitor of 4.7nf. The internal structure of the ADC is a switched
capacitor SAR ADC, where the charge for the sample and hold capacitors internal to the ADSP-CM419 required external
charge to hold the charge in the ADC for the conversion time as specified. Ensure these are in place in the schematic.
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