Hi,

I am trying to find out some ADSP21469 parameters to design a PCB, these are Edge - RiseTime and Zoutput of different pins (DDR2, DAI, and so on) in order to calculate line terminations, etc. I am looking at the data sheet but i cannot find them. I can find some data as timing requierements but not RT&Zout.

I am newbie on this, so i would appreciate some help on this matter!.

Thanks in advance and happy Xmas.

Carlos M.

Hi Carlos,

Sorry for the delay in response.

Regarding “I am trying to find out some ADSP21469 parameters to design a PCB, these are Edge - RiseTime and Zoutput of different pins (DDR2, DAI, and so on) in order to calculate line terminations, etc.

The same with output impedance, some figures show current vs voltage but i am not sure to figurate out Zout from these in data pins..”

>> As far as my understanding is there, the IBIS file provides the V-I characteristics for all the pins. In order to compute the output impedance of a pin, you can drive a pin to a particular voltage and can measure the current drawn for corresponding voltage. Hence V/I will give you the correct characteristic impedance of the pin.

Apart from this, there is no such formula which will help to evaluate the exact output impedance of the pin in an IC.

You may follow general board design guidelines to decide whether or not you need a series termination on these signals and if needed what exact values should be used. Hence I would suggest you to do signal integrity test and derive values for the custom board. The values for the series resistor can be determined by simulating with the IBIS models.

The link for the IBIS file is given below:

http://www.analog.com/en/processors-dsp/sharc/products/mod-ibis-models/resources/index.html

Please let me know in case you have any further queries/doubts.

Thanks,

Harshit