filter construction of dir1703

[takashi]

hi,
i have done a pcb of dir1703, i find that the filter construction is different between the datasheet (c7, c8, r2)and EV board user menual(cf1 cf2 and rf1).

which one is correct? or both can be used?

thanks

 

[Brian Brown]

Re: DIR1703 PLL Filter

Use the filter example shown in the DIR1703 data sheet:

R2 = 1.2K Ohm
in series with
C7 = 0.068uF

and

C8 = 0.0082uF

I believe the schematic shown in the DEM-DIR1703 Instruction Manual is wrong. Besides the fact that it doesn't match the part's data sheet, the values don't make any sense from a functional standpoint.

Also, this is further confirmed by other TI eval boards using the DIR1703 (such as the TAS5100EVM) that show the same filter values as the data sheet.

Regards,
Brian.

 

[takashi]

thank you very much, Brian Brown

and one more question, can i connect the coxial/BNC s/pdif to Din(pin20) of DIR1704 directly?

 

[Brian Brown]

and one more question, can i connect the coxial/BNC s/pdif to Din(pin20) of DIR1704 directly?

No.

Unlike many of the Crystal parts, the DIR1703 requires an external receiver circuit.

This makes the circuit a little less convienient to design, but using an external receiver makes it possible to achieve better impedance matching to the incoming line and also better noise rejection.

Brian.