MCLK (22/24MHz) signal transfering. Distance 25cm.

Dalius · 21st April 2004, 07:43 AM

In Pioneer DV-444 (DVD player) clock supplied from PLL (see picture).
PLL MCLK signal to DAC (PCM1742EK BB) is connected with 16 cm length wire (PCB trace).
Signal in scope (MCLK near PCM1742) looks bad.
Also I want to connect CS4392 (DAC) in parallel. Distance from PLL to CS4392 DAC is about 25cm.

How to transfer MCLK (22MHz) signal to second DAC with minimal additional jitter and minimal distortion?

Elso Kwak · 21st April 2004, 05:12 PM

Hi, 50 Ohm or 75 Ohm coax properly terminated at the receiving end. Horowitz second edition page 611 & 879.

jwb · 21st April 2004, 05:19 PM

Agree with Elso, try MMCX or Hirose u.FL micro connectors and the proper size of coax, and make certain to match termination.

Bricolo · 21st April 2004, 06:37 PM

Why only properly terminated, and not also properly started?

Elso Kwak · 22nd April 2004, 06:06 AM

Quote:

Originally posted by Bricolo
Why only properly terminated, and not also properly started?

Bricolo,
If you mean double terminated and you are satisfied with halved signal levels.......

Dalius · 22nd April 2004, 06:55 AM

Hi,

Thanks for replayes.

When 50 or 75 Ohm terminator is connected to ground at receiver side, it take current.
PLL supply is 3,3V. If logical 1 is 2,5 volt, then current in 50 Ohm terminator will be 50mA.

This amount of current is acceptable for CMOS PLL ?

Bricolo · 22nd April 2004, 07:04 AM

Quote:

Originally posted by Elso Kwak

Bricolo,
If you mean double terminated and you are satisfied with halved signal levels.......

I know

But that's what I learnt at school. Transmission lines have to be double terminated in order to work properly (no reflection on both sides)

Ouroboros · 22nd April 2004, 07:09 AM

If you only intend for the signal to go in one direction, it's perfectly OK to drive from a low impedance and terminate in the characteristic impedance of the cable. This will prevent any reflection.

On dc biased signals, you might find a C-R termination better, or a termination biased to Vcc/2.

Elso Kwak · 22nd April 2004, 09:30 AM

Quote:

Originally posted by Bricolo

I know
But that's what I learnt at school. Transmission lines have to be double terminated in order to work properly (no reflection on both sides)

Now what are you going to do about it?
Lay it on the line!

21st April 2004, 05:12 PM	#2
Elso Kwak Banned Join Date: Dec 2001 Location: Zamboanga, City of Flowers, Mindanao	Coax Hi, 50 Ohm or 75 Ohm coax properly terminated at the receiving end. Horowitz second edition page 611 & 879.

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21st April 2004, 05:19 PM	#3
jwb diyAudio Member Join Date: Mar 2002 Location: San Francisco, USA	Agree with Elso, try MMCX or Hirose u.FL micro connectors and the proper size of coax, and make certain to match termination.

21st April 2004, 06:37 PM	#4
Bricolo diyAudio Member Join Date: Nov 2002 Location: Grenoble, FR	Why only properly terminated, and not also properly started?

22nd April 2004, 07:09 AM	#8
Ouroboros diyAudio Member Join Date: Dec 2003 Location: Nottingham UK	If you only intend for the signal to go in one direction, it's perfectly OK to drive from a low impedance and terminate in the characteristic impedance of the cable. This will prevent any reflection. On dc biased signals, you might find a C-R termination better, or a termination biased to Vcc/2.

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