CDCM6208: Unused output and unused power rail

Hirotaka Matsumoto

Part Number: CDCM6208

Hi all

Would you mind if we ask CDCM6208?
The customer will use Output0 and 1.
So, we would like to know the termination of unused outputs and power rail.

<Power rail>
They should tie unused VDDO pins to ground thru 1kohm resistor.
Is this correct?

<Output>
We assume that it depends on output type CML, HCSL, LVCMOS, LVDS and LVPECL.

HCSL, CML, LVDS and LVPECL : It should terminate the unused outputs with 100 resistor across the differential pins?
LVCMOS : Open?

If you have some advice, could you let us know?

Kind regards,

Hirotaka Matsumoto

over 5 years ago

0 Shawn Han over 5 years ago

TI__Genius 9920 points

Hi Hirotaka,
I assigned your questions to our application engineer. Thank you for your patient to wait for his reply.

Regards,
Shawn

0 Patrick Kammermayer over 5 years ago in reply to Shawn Han

TI__Expert 5325 points

Hello Hirotaka-san,
you can leave unused supply pins open.

About the output pins: this depends on your start-up requirements. If the device is powered up in a ROM page (pin strap mode) or when you re-program the device without keeping the outputs disabled using the SYNCN pin or you want to avoid any unused outputs from disturbing used outputs: yes, then please terminate them using the appropriate termination. For HCSL this would be 50 Ohm to GND. For CML, LVDS, LVPECL you can use 100 Ohm differential termination. For LVCMOS you can just leave the pin open or re-use as a test point with a probing pad.

My recommendation is to switch off any unused outputs by disabling the respective output buffer and (if possible) the channel divider. (e.g. Use Y0, but do not use Y1 --> you can only disable the output buffer of Y1).

Best regards,
Patrick

0 Hirotaka Matsumoto over 5 years ago in reply to Patrick Kammermayer

Guru 27525 points

Patrick san

Thank you for your help.

Kind regards,

Hirotaka Matsumoto

Clock & timing

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CDCM6208: Unused output and unused power rail