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Original question:

Unstable Video Output when using 24bit RGB video input.

DLPC350: Using a sequential RGB buck converter

Jim Teunis
Intellectual 290 points
Part Number: DLPC350
Other Parts Discussed in Thread: DLPC6401, DLP4500

Hello,

I am designing a board around the DLPC350. My application is video display. I want to make sure I understand the PWM outputs correctly.

Am I correct in saying that the EN outputs for the three (R, G & B) LED channels will be enabled sequentially, i.e. there will always be only one active at a time? Because this would mean I can use a single buck converter and sequentially power the three LEDs instead of using three separate buck converters.

I found the PMP4326 design resource, but I still haven't found a 100% conclusive answer to my question.

Looking forward to your reply,

Jim

  • 0
    TI__Mastermind 23070 points

    Hello Jim,

    Welcome to DLP forum and thank you for your interest in DLP technology. Could you be please more specific about end product? So that you could choose right chip-set for your application.

    The DLP technology is chip-set solution;  a combination of controller and DMD are targeted for specific application.  If you application is purely RGB video and projection display then you may want to  consider  DLPC6401 controller with DLPC4500 DMD.

    https://www.ti.com/product/DLPC6401

    DLPC350 controller along with DLP4500 DMD is targeted for light control applicator.  This  chip-set will also support video display , however the firmware especially sequences (DMD mirror switching) may not be  optimized for video display image quality (Human eye).

    You observation about sequencial color (LED turn on one at time) is correct and you can design the driver that way and it will work. 

    However, only DLPC6401 does supports color overlap (Brilliant color). In this mode , you will get additional brightness. In that case, the LED driver circuity needs to support two LED on simultaneously.

    Please refer to DLPC6401 programmer guide for details of "Brilliant Color"

    https://www.ti.com/lit/ug/dlpu012a/dlpu012a.pdf

    regards,

    Vivek

  • 0 in reply to Vivek Thakur
    Intellectual 290 points

    Hello Vivek,

    Thank you for your quick reply.

    My application is displaying commerials and videos in a small room. Perhaps the DLP4500 DMD is not the most obvious choice for this application. The reason that I am using this DMD is that I need a relatively high throw ratio because the distance from the beamer to the projection screen is only about 1 m. The only 'off-the-shelf' optical engines I could find that features a high-ish throw ratio uses the DLP4500, so this is the reason I will use the DLP4500.

    Thank you for pointing me to the DLPC6401, I was under the assumption that I had to look under 'high speed visible' to find components that are compatible with the DLP4500 DMD. I am very happy to find a simpler and less expensive device that will fit the bill. I will not need the brilliant color for now so I will design a sequential LED driver.

    Thanks again,

    Kind regards,

    Jim

  • 0 in reply to Jim Teunis
    TI__Mastermind 23070 points

    Hi Jim,

    I am glad we were able to assist. Please let us know if you have additional questions.

    regards,

    Vivek