Lightcrafter4500 PCB routing length

One more thing I would like to confirm.
Both DLPC350 and DLP4500NIR datasheet indicates DLPC350 "package skew" for DMD interface. And said varied 0 to over 175mm.
Should it be "mil" not "mm"?
And these are routing length inside DLPC350 package that we should consider these number with PCB routing length?
We do not need to care inside DMD package rounting skew, do we? If yes, is there any values as same as DLPC350?

Regards,
Takeshi

Hi Takeshi,

I found a good app note describing the package skew you're asking about: http://www.ti.com/lit/an/scaa055/scaa055.pdf 

The package skew is the variation in delay from one copy of the device to another. It does seem like the units should be mil, not mm. I'll take a look into that. However, the datasheet says:

"To increase the system timing margin, TI recommends that the DLPC350 package variation be compensated for (by signal group), but it may not be desirable to compensate for DMD package skew. This is due to the fact that each DMD has a different skew profile, making the PCB layout DMD specific. To use a common PCB design for different DMDs, TI recommends that either the DMD package skew variation not be compensated for on the PCB...."

Therefore, I would not worry about the package skew in your design.

As for the flex length, it should be within the requirements given in table 19 (DLPC350 datasheet). These values have been tested by TI. Any values outside of this range might work, but there is no guarantee.

Hope this helps,

Paul

Hi Paul,

Thank you for introducing me the app not. It seems to be general information.

However, since we will make our Own DMD board & DMD cable, we think we need to know "actual PCB routing Length of Lightcrafter 4500" to satisfy your routing constrain. Do you have this information? Or any other way to help?

What I understood other topics: (this is just the confirmation)

1: The "Unit" of DLPC350 package skew indicating in the manual is "mil" not "mm"

2: We can ignore DMD package skew

3: We should consider DLPC350 package skew + Lightcrafter 4500 PCB routing length + Cable length to DMD

Regards,

Takeshi

Takeshi,

Yes, the app note is general information. I just found the definitions useful and thought you might as well.

If you're making your own DMD board and cable, then the length of the PCB traces and flex for your board must be able to meet the guidelines provided in Table 14 (section 10.1.7.3) of the DLP4500 datasheet. How the LCr4500 is routed doesn't apply to your case.

On your other topics:
1. I'm not sure what the proper units are for package skew, I'm going to look into this. I agree with you that mil would make more sense.
2. Yes
3. You should consider the length of the cables to the DMD + PCB routing length. Ignore the package skew unless your design has extremely tight requirements.

Thanks,
Paul

Hi Paul,

Thank you for your kindness response!

However because of my skill to understand, would you mind reconfirming my understanding?

Based on the Routing Constrain (including table 14), we need to care for the "length" as...

(1) DLPC350 package skew + (2) DLPC350 PCB trace length + (3) DMD flex cable length + (4) DMD board trace length

Therefore if we use Lightcrafter 4500 as a controller board and re-make DMD flex cable and DMD board, then we need to take (1) & (2) into account to make our "DMD flex cable length"(3) and "DMD board" (4). We have data of (1) describing in the datasheet (Table 14), so the rest thing we should know is "Lightcrafter 4500 PCB routing length" (2).

Since I understand as the above (may have some misunderstanding..), I'm asking if you have Lightcrafter 4500 PCB routing length. Please advise me... sorry about that.

Other topics: Please double check and respond me the "units" for package skew descrbe in both DLPC350 and DMD datasheet.

Regards,

Takeshi

Takeshi,

Thanks for the clarification, I'm sorry that I didn't understand earlier. You'd like to build a flex cable for the Lightcrafter 4500 and need to know how long you can make the flex.

You care about: (1) DLPC350 package skew + (2) DLPC350 PCB trace length + (3) DMD flex cable length + (4) DMD board trace length

I'm going to recommend that you go to the Lightcrafter 4500 reference design: www.ti.com/.../tidc086

There, you can find the Gerber files (and the .BRD file) which will help you determine the lengths of all the traces on the board and you will be able to accurately design your system.

Thanks,

Paul

Paul,

Thank you for the clarification, too.

However, why did you deleted (1) DLPC350 package skew? If we measure PCB trace length from your design file, I think we still need to care (1) described in the datasheet. For example: DMD_D0 line(152.35 mil), if we measured by your design file as "1000 mil", and the total routing length constrains as 2480 to 2953 mil, so we have to make new DMD cable with taking DMD cable length itself & DMD board trace length into account (1327.65 to 1800.65 mil).

min: 1327.65 = 2480 - (152.35 + 1000)

max: 1800.35 = 2953 - (152.35 + 1000)

About the unit I told you, I found older datasheet (rev.C of DLPC350) described as "mil". And there is no revision histry indication that you change from "mil" to "mm", so we can conclude that Rev.D datasheet is typo and should be "mil", right?

Regards,

Takeshi Yuasa/TED

Paul,

Thank you. I understood. We will ignore the package skew and we just measure one of the DMD I/F the length of Lightcrafter 4500 PCB routing, then will make our DMD cable sensitivly same length.

Regards,
Takeshi