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Erratic BOM in AD9644-155 evaluation board

Question asked by koivari on Feb 14, 2013
Latest reply on Feb 15, 2013 by J.Harris


We have two AD9644 evaluation boards






SNO: 102411A


The AD9644-80 board is working OK.

The AD9644-155 board clock oscillator Y502 was found to be oscillating at 26.7 MHz, not 80 MHz as expected.

When digging into the oscillator problem, it was found that 3P3V_ANALOG is at 2.0V.

The reason for this is, that R506 pulls low the internal regulator of the AD9524 - thus loading the 3P3V_ANALOG voltage.


In the AD9644-80 board, R506 is not assembled, and there is no problems.

In the AD9644-155 board R506 is assembled, shorting U501 pin 12 to ground via R508.


The problem can clearly be seen in the schematic 9644CE01, where R506 - R508 create a path to ground from the LDO output.

Are you aware of this problem ?

Are there other differences between these two board BOM versions ?

Can I have a correct schematic for the AD9644-80 board ?

Do you think the AD9524 on my board is now damaged ?


regards Miika K