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Visitor divs321ec
Visitor
2,263 Views
Registered: ‎02-22-2010

mixed mode implementation of Built In Self Test

Respected Sir

how to implement mixed logic in built in self test circuit ...

i have implemented digital part  now....

Digital part has 3 blocks inside

First block generates test vectors which is implemented using LFSR's(Linear Feedback Shift Register)... The output of this is connected to Circuit Under Test where any combinational or sequential circuits can be tested.

The output of this is connected to Signature Analysis circuit which is nothing but modified LFSR. the output of this block is called Signature.

This is only digital implementation.

 Extension of this has to be done.I should convert this into Analog output by using Digital to Alalog Converter...

How to do this.........I got struck in this part Sir 

 

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1 Reply
Advisor eilert
Advisor
2,255 Views
Registered: ‎08-14-2007

Re: mixed mode implementation of Built In Self Test

Hi,

BIST for digital  circuits using LFSRs is quite common, and it seems like you have solved this alredy.

If you are going to expand this to the analog world you need to consider a few things:

 

1.) the ADC/DAC. These are separate parts with their own specified interfaces.

So you have to check the datasheets to see what kind of interface you have to build in order to transfer your data to/from the analog world. (parallel, i2c, spi....)

 

2.) Noise. While the response values of a digital circuit are well defined (either 0 or 1 at a given time for a given stimulus) you have to define a tolerance range for the analog result value.

The ADC and DAC give you about 1 Bit of signal error, then you have nonlinearities there and your DUT adds some noise and tolerances too.

So in the end when you apply a certain Voltage Uin to your analog circuit, the resulting output voltage Uout has to be defined as a range like:

     If expected Uout=5V then 4.8 ... 5.2V may be the acceptable range during the BIST.

  This can be acheived easily by ignoring some of the LSBs. Howmany? That depends on the circuit.

 

Have a nice synthesis

  Eilert

 

 

 

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