With any power supply, the resistance from the grid is a critical consideration.

When conducting EMIR repairs, an significant amount of time is spend making sure every point meets a minimum threshold.

One area you do not want to wait to fix are are the power plan for a RGB DAC.

The work you do in this area should take precedence other areas in your top level planning and not be left to the dregs of your final work.

The power going to these DACs are often coming directly from a BONDPAD or BONDPADS and resistance to each one is required to be equal in resistance.

The circuit designer will know what the current requirements* are so you can establish a safely performing width to handle electro migration, and you will want to ensure the resistance and distribution are identical to each RBG DAC.

*The current requirements may not demand as much wire width as you may think; however, do not leave this to chance. Know the worst case current requirements and how this affects your routing.

Matching distribution within each DAC should be clear as the current sources cover a large area and taps should not only be numbers but they need to be IDENTICALLY placed. Vias schemes should be instanced or an integral part of each DAC and none additional placed above to ensure matching performance.

Tapping into this Identical DAC power grid needs to be consistent in terms of resistance as a first order.

Between the bondpads for the special power and the DACs ideally should also be identical, however, there may be some cases where this is not possible. Hence, adjusting the power bussing between the pads and the DACS must be equal resistance. Making the resistance equal may require lengthening, shortening, and adjusting widths in effort to achieve an equal square count of metal.

If special bond out power is not available in your chip plan, you will need to tap into a common VDD supply, in this case, you must run a wire directly to the bondpad and NOT tap into a common chip power grid ANYWHERE in order to eliminate random noise. Running directly to the bondpad will help filter out the noise from the other circuits connected to the common VDD that can be used for the DACs.

The aforementioned are the considerations on-chip.

From the package point of view, any asymetry in the routing of these power supplies can effect the balance to the DACs, because the length or asymetrical doubling of the bonding runs, their resistance, can greatly affect the overall resistance and destroy the on-monitor performance.

Yes, the outputs of the DACs are important, but we’re just talking about power supplies.

***

Dave Campbell, an analog engineer who joined IDT from National Semi way back when, used to say, “There are two kinds of Draftsman, the kind who don’t complain and then don’t do what they’re instructed to do, and those who complain and end up doing what they are instructed to do.”

***

Feel free to Like, Share, Follow, and Comment (without using AI)

CKY

***

Copyright © 2023 Challen Yee / ICLayout.blog  Some Rights Reserved

Disclaimers