Other Parts Discussed in Thread: SRC4392, PCM1794, SRC4192
Hello,
I recently upgraded my DAC product. The new board is similar to the old board except that it has an SRC4392 instead of an SRC4192 and it uses the integrated SRC4392 line receivers rather than an external receiver chip. Both use a PCM1794. An EMI problem with the new DAC board has been uncovered in beta test and I wonder if the SRC 4392 has any special considerations to take note of.
The symptom is that when an EM disturbance happens, the signal on pin 45 of the SRC4392 abruptly goes away for about 300mS and then abruptly returns. Abruptly means that it is immediate and not gradual, like when muted. An EM disturbance can be either touching the DAC ground with a test lead, or switching on/off a device like a lamp plugged into the same power strip as the DAC power supply, or triggering a Zerostat static elimination device. The test configuration is SPDIF input on Line Receiver 1 (pins 1 and 2), and output from Audio Serial Port B (pin 45).
When the problem happens, there is no disturbance on the input or the reset or the I2C control interface. Something is going on internally in the SRC4392. I suspect that there may be a disturbance on the power inputs although I have pins 9, 17, 33 and 42 each bypassed with a 10uF electrolytic and 0.1uF ceramic. The board has 4 layers, one of which is an internal ground plane (same as the old board).
Any thoughts on what I am dealing with here are deeply appreciated.
Regards,
Dave Davenport
