• State TI Thinks Resolved
  • Locked Locked
  • Replies 1 reply
  • Answers 1 answer
  • Subscribers 20 subscribers
  • Views 2589 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LMK00334: how to terminate 50Ohm at HCSL operation, DC coupling

Noriyuki Takahashi
Genius 9850 points
Part Number: LMK00334

Hi team

I have questions about how to how to terminate 50Ohm at HCSL operation, DC coupling for LMK00334.

Please see the attached. And could you support these questions? We want to replace 9DML0451AKILFT with LMK00334.

LMK00334.pptx

Regards,

Noriyuki Takahashi

  • 0
    TI__Expert 6920 points

    Hello Noriyuki-san,

    Typical HCSL output requires 50 Ohm termination from each lead to ground due to a 15mA current source being derived from an open emitter. Since traces have a matched impedance of 50 ohms, signal reflection will be absorbed at the source. The 'Rs' resistors function as overshoot correction, slowing the rapid rise from output.

    Answering why we show terminations on the source end, the typical use case of HCSL output is for PCIe applications and other Intel chipsets, terminations are not impacted due to long traces and in some cases the chip includes the HCSL termination at the output because of this.

    We can definitely use terminations near the receiver and this could improve performance if long traces are used but in normal HCSL use we want to keep traces on the same PCB and as short as possible to reduce attenuation and reflections.