Hi
I have used PCM1802 in it’s basic application (schematic and photos of the issue under a link: https://drive.google.com/folderview?id=0B1h4rvw56X8CflJtU0Y5NFJwX2FpcWRtdmNKVUp1ZlR0TzBGU1Q1dm1ZR1FBUnhDelJFajg&usp=sharing )
It’s a transmitter powered from single mains plug power supply there are two voltages on the board +3.3V and +5V refereed to the same ground.
According to the data sheet on pin three there should be reference voltage of half of Vcc that is approx +2.5V.
Clocks are supplied externally by wireless module, currently no DATA is present (which doesn’t surprise me since Vref is not correct.
What is surprising is that on previous build (some months ago) I had the whole thing working fine, but after I passed the PCB to our subcontractor for him to fit it into an enclosure the module stopped working probably due to handling.
On photos you will see two prototypes from the same batch which I received yesterday, they were powered and voltage vas measured on pin 3, supply voltages were also measured they are +3,3V and +5V, +3.3V comes from +5V by series regulator, +5V is obtained from a series regulator as well from +7.5V mains plug supply voltage.
Why such a simple application cause such anomalies? (one picture shows negative voltage where only positive is available)
What can be done to fix it?
Best regards