AD9265 BIST Function

Document created by analog-archivist Employee on Feb 23, 2016
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I am using the AD9265-125MSPS. I would like to confirm correct operation of the
part by using the BIST (built-in self-test) PN9 or PN23 (pseudo-random noise)
sequence generator. Could you please document how to use this BIST?

 

BIST (built-in self-test) provides a simple means of determining, in a
pass/fail manner, if the device is functioning.  A BIST feature is included
that verifies the integrity of the digital datapath of the AD9265. When BIST is
enabled, a PN sequence is fed to the digital block of the converter. The output
of the digital block is added to an accumulator that was cleared at the start
of the BIST cycle. The accumulated result consists of the sum of all PN
sequences passed through the digital block. If the converter core is
functioning properly, it responds exactly the same every time it is called.
Therefore, the results should be consistent.
The results are placed in the MISR registers found at 0x024 and 0x025. The user
can read these registers to determine if the digital section of the chip is
functioning properly. This is done by comparing the values read with the values
stored in the test code.

The steps required to use the BIST function are outlined below:
BIST Enable Register 0x0E
1. Set Bit 2 to 1 (to clear MISR or reset BIST Sequence)
2. Set Bit 1 – Bit 0 to  01 (BIST Mode Enabled)
Test Mode Register 0x0D
3. Bit 3 – Bit 0 to 0101 (to select PN23)
-or-
4. Bit 3 – Bit 0 to 0110 (to select PN9)
When this register is set, test data is available on output pins. BIST Mode
lasts 512 clock cycles
MISR Register
5. 0x24 BIST signature LSB [7:0] (contents should be non-zero due to being
pseudo-randomly generated)
6. 0x25 BIST signature MSB [15:8] (contents should be non-zero due to being
pseudo-randomly generated)

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