Defects in ADC data, and timing of 1.8V analog supply & 3.3 V digital supply

Question

Hello, 
 We are using a AD9266 in one of our products and dealing with some bad data from the ADCs. While investigating, I noticed that on the boards that produce bad data, the analog supply comes up at about 35 ms after the digital supply. While on the good boards, the analog supply comes up about 8 or 9 ms. 
 I couldn't find anything in the data sheet about timing requirements for when these voltage rails should be stable. Could a delayed analog supply voltage cause issues with the AD9266? 
 Marten

PMH2023 · Accepted Answer

Hello, My comments/questions are as follows: 1) The device name with "-40" indicates that the part is capable of up to 40 MSPS operation while meeting datasheet specification. Can it be assumed that your application is below or equal to this sample rate? 2) The different speed grades of 20/40/65/80 MSPS is set during factory test where a power bias register is set permanently with higher power settings required to achieve rated performance at higher sample. The part is branded with the "-X" to designate the speed grade to which the power bias has been set too. On very rare occasion, we have seen that the wrong branding designator was applied to the device such that a part set for a 20 MSPS setting may be branded with the 40 MSPS or higher settings. Not saying this is your situation but a simple test (assuming you can easily lower your sample rate) would be to see if the "suspect" part works consistently at 20 MSPS. If it does.......this would be strong indication that this may be the problem. 3) The fact that the "suspect part" exhibits the same problem on both boards while a "good part" remains performing good in the same socket where the suspect part was soldered indicates the problem is with the part itself. How many boards have been built and tested to date and how many of these boards with AD9266-40 device exhibit this problem? Perhaps it is worth discussing with ADI if one (or more) of the suspect devices get returned for to our failure analysis of which they are retested on our ATE (after visual inspection) to see if they perform within our datasheet spec limits. Note that JAlipio would need to follow up with you on how make Failure Analysis request.)

JAlipio · Answer

Hi mtbeels 
 Thanks for using AD9266. 
 Although the datasheet does not explicitly specify power sequencing requirements, it is generally recommended to bring up AVDD and DRVDD simultaneously. 
 Additionally, have you tried performing a digital reset by writing 0x03 followed by 0x00 to register 0x08?

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Defects in ADC data, and timing of 1.8V analog supply & 3.3 V digital supply

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