Hello Again, Thanks for your answer. The customer measured 50Mhz at input of the ADC after switching the ADC on. Switching off the ADC or switching off the clock removed the problem completely. There was no 25MHz. He measured this using a special preamp he normally uses for EMC probes and a Lecroy scope in spectrum analyzer modus. They don't think they are missing bits due to the following: - missing a bit would result in abrupt jumps of the signals - If it was a deserializer problem the result would at least change now and then: 0 would become 1 and vice versa. Our problem is extremely regular and therefor seems fully clock related. - When looking at the noise it is clearly centered around zero. This would imply that the sign bit (they are using two's complement) would be erratic (not one of the LSB bits) but if you look at the measured sine wave you will see that nothing is wrong with that. - When looking at the sine signal they see the same modulation on 4 chips, all 32 channels when terminated with 50 ohm. - The 50Mhz signal is coming from the chip, if it is measured by the ADC with 25MHz then this will result in a + - modulated signal which is locked to the clock. - They looked at the ramp test signal but they are only able to measure 4096 samples. Results looked good. They are currently not able to do new measurements as they on their summer holiday. I hope this info, will help you, please ask extra questions if needed. Regards, Meir.
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