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Question asked by bgrigor on Jan 31, 2015
Latest reply on Apr 22, 2015 by AshrafS


Recently we purchased AD9277 ADC for one of our projects.
In stage of development we find out some mismatches of technical details and descriptions given in the datasheet of the ADC.

  1. The ADC has 14 bit resolution. The parameter DCO to Data delay (tdata) is equal (tsample/24)-300 regarding to the table of switching specification. But in reality it should be divided to 28 (14 bit x 2). In comparison with an another ADC - 9276 which is 12 bit ADC, for the mentioned parameter it's mentioned the same value, which is incorrect, because the resolution of the ADCs are different.
  2. In the timing diagram of the AD9277 (page 9) FCO and CLK should be equal (see top of second chapter in page 37). But in the timing diagram they are not equal. One full cycle of clock should carry 14 bits. Regarding the timing diagram FCO one period is carrying 14 bits but CLK carrying 12 bit. If compare the timing diagram of AD9277 with timing diagram of AD9276 FCO and CLK are equal and both of them are carrying 12 bit data.
  3. For both of mentioned ADCs (AD9276, AD9277) it's mentioned that DCO±  is equal to six times the sampling clock rate (top right chapter in the page 37). But in our understanding for AD9277  DCO± should be equal to seven times of the sampling clock (DDR mode, 14 bit).   

In the datasheet of AD9277 there are some this kind of mistakes which seems are result of updating of the datasheet.
As I'm supposing AD9276 is the old generation of such kind of ADCs.
When AD9277 released it used updated version of the datasheet for his previous analog, which was AD9276 and some parameters were not changed in the datasheet.

Also we tried to communicate with settings registers of the ADC and also faced with some problems.

Some of the registers are working properly, we can read and write data. But some of them are not.

Particularly, default values of registers 0x02 and 0x18 are not met the values mentioned in the datasheet.

We can write data to the register 0x11 but when we are trying to read we are getting the default value.

May be the register map is changed in comparison with AD9276 but in the datasheet they are not updated.

Does anybody have the similar problems or have a new datasheet of AD9277?

Thank you.