i designed the PCM1681 circuit followed by the datasheet, and sclk bck lrck datain1-4 are all came
from a fpga . but once i input the sclk in the pcm1681's 5 pin(sclk)(the other input pins are float) , the dataout 1-8 are all output shaped wave between the 2.5V voltage. and the shape is like the Square wave . when i input the bck ,lrck and datain1-4 , the output is ok except the Square wave is still there.
i don't know why this happen, have u see this before? thx a lot!.
When you apply the SCLK (and no other signals), are you powering the IC?
For the second case, where you have valid clocks and data in, what is the frequency of the output square wave? Can you post some scope shots to illustrate what you're seeing?
In reply to Don Dapkus:
yes , I powered the IC when apply the sclk.
and i take a picture about the dataout as below. As the picture show, the average voltage is the correct output , but some wave like squares are surrounded . and the square is about some multiple of sclk.
i am just thinking if the wave is because I just put a serial cap of 22uF behind the output but without a LPF circuit and a load large than 5kohm?
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