Hi Bradley, Thanks for the feedback. The datasheet lists the min SCLK frequency as 1 MHz, because that was how the part tested and qualified. We have found that the part will function properly with lower SCLK frequencies, but have not characaterized it. In our testing of the part, we use a TI WaveVision5 to communicate with the LM98640. The SCLK frequency from the WV5 board is 41 kHz. In this setup, a signal on INCLK was not required to communicate with the LM98640 SPI. It may be possible at higher SCLK frequencies, that INCLK is required. I will update the post with these details. The statement about False Lock was in reference to once the part was up and running properly. The False Lock and DLL Reset were designed in for cases when the DLL might lose lock due to an external factor such as ion strike. It was found that in those cases, the DLL would automatically relock and the DLL reset was not needed. In addition to Christian's comments: I agree that it is likely that you are likely getting a good INCLK signal. You can verify it by probing at test points TP22 and TP23. The LM98640 does not have power on reset, and all registers must be written after power up. Also see the datasheet for the order of writing the registers. This can make a difference sometimes, depending upon what mode you are putting the part in.
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