Showing results for

- Intel Community
- FPGAs and Programmable Solutions
- Programmable Devices
- Impedance Matching for differential tracks

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page

SMS

Beginner

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

11-19-2018
10:13 AM

1,960 Views

Impedance Matching for differential tracks

The Max 10's LVDS IO user guide mentions matching trace impedance with that of termination resistor. However in the figure given below they have mentioned single ended trace impedance of each of the differential traces to be 50Ω and terminating resistor's value as 100Ω.

Now how can the differential impedance of traces be matched with that of termination resistor given that differential impedance is defined as

where,

Zd = differential impedance

Zo = single ended impedance

d = trace separation

h = dielectric thickness

I have tried to evaluate from the above equation using some standard values of h but didn't end up with 100Ω differential and 50Ω single ended impedance.

Link Copied

5 Replies

Abe

Valued Contributor II

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

11-23-2018
01:07 AM

101 Views

The termination scheme used in LVDS lines forMAX10 follows a 3-resistor or single-resistor external termination scheme. You can refer to the following LVDS termination guide lines for more information.

So, when you use the scheme mentioned above you will have to keep the line impedance at 50ohm and 100ohm and then calculate the values of Rs/Rp depending on the type of scheme used.

Rahul_S_Intel1

Employee

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

11-23-2018
05:18 AM

101 Views

Hi ,

Also try to use the IBIS simulation .

Regards,

RS

SMS

Beginner

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

11-23-2018
05:47 AM

101 Views

Thanks for replying.

@Abe

The three resistor termination scheme needs to be employed only in case of emulated transmitter. I am more interested in the termination for a receiver and the impedance of the LVDS lines, both single ended and differential.

Sure. Will try. Any tool you recommend? Have tried Hyperlynx before but because of unavailability of IBIS models for some components other than MAX10, had to drop that idea.

Rahul_S_Intel1

Employee

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

11-23-2018
05:50 AM

101 Views

SMS

Beginner

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

11-23-2018
07:52 AM

101 Views

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page

For more complete information about compiler optimizations, see our Optimization Notice.