DS32EL0421 - the resistor of VOD_CTRL pin

Hiroshi Katsunaga

Mastermind 6480 points

Other Parts Discussed in Thread: DS32EL0421, DS32EL0124

Hello,

My customer has a question about DS32EL0421.

[Q]

Please tell me how to decide the resistor value of VOD_CTRL.

My understanding is as follows.

・It should usually choose 9.1kOhm when a DS32EL0421 is directly connected to a DS32EL0124.

・If the insertion loss is big, users can control the strength of the de-emphasis.

Is my understanding correct ?

Best Regards,

Hiroshi Katsunaga

over 10 years ago

0 Mike Wolfe over 10 years ago

TI__Expert 3050 points

Hi Katsunaga-san,

There are many reasons why customer may want a different output VOD. Setting the VOD with a 9.1k Ωresistor is just a typical value that works for many applications.

Customer can use VOD and the de-emphasis control to increase the cable reach of their system. The formula from the datasheet's CML Launch Amplitude section is:

R = (1400 mV / VOD) x 9.1 kΩ

Mike Wolfe
DPS APPS / SVA

0 Hiroshi Katsunaga over 10 years ago in reply to Mike Wolfe

Mastermind 6480 points

Hi Mike,
Thank you for your fast response.
I understood your comment.

Best Regards,
Hiroshi Katsunaga

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DS32EL0421 - the resistor of VOD_CTRL pin