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Just one thing to point out about that application note:

If you need to support a standard 2 channel LVDS system, the DS90C387A is fine. If you need to support a 2 channel Open LVDS Display Interface (OpenLDI), then you will need the DC-balance mode found in the DS90C387.

Mike Wolfe

DPS APPS / SVA

Hi Everyone,

It is possible to build an interface for quad lvds signal to dual lvds (same pixel clock)?

thanks.

Greetings -

Please expand on this request more, it is not clear.  As Mike noted the DS90C387 is a dual pixel LVDS SER, it can take in 24 bit RGB at say 150MHz, and outputs a dual pixel (8D+C) LVDS interface at 75MHz (since it is twice as wide, aka dual).

I an not clear on what you mean as "quad LVDS to dual LVDS (same pixel clock)", if going from 4 to 2, then for equal bandwidth the clock will also have a factor of  2.

John Goldie
Video Interface - DPS / SVA

Hi Rosse,

Does TI have 1-chip solution to bridge HDMI to LVDS? Thanks!

Howard, no, only the 2-chip solution for this function.

Best regards,
RE

Hi, for a project of mine I am trying to build a HDMI to LVDS solution in order to control a screen with the following characteristics:
- 1280x800 resolution
- 89 MHz pixel clock
- 6-bit per color

I bought a SN75LVDS83B and a TFP403 as suggested, however, I am now reading through the datasheets and, even if the LVDS transimitter has an option for 6-bit per color data, the TFP403 does not seem to support it. Is that so? Is there any workaround to make it work?
Thanks!

Giulio,

These two devices deserialize and serialize 27 bits.  You can simply use a subset of these available bits if you're using 6-bit.  Just drop off the LSBs.  The DVI standard always uses 8-bit.  Your graphics source could conceivably generate 18-bit color data with the LSBs held low, and then leave the corresponding TFP403 outputs floating.

Best regards,
RE

Peter,

I have seen that you have successfully turned on an LG 23" using TFP401A and DS90C387A. I am also working on such a solution, driving a flat panel with lvds using dvi input from some graphic gard. Do you have some tips for me before starting schematics? I have read the guidelines from TI and for the mentioned chips, but more tricky information would be helpfull.

Regards,

Juergen

Juergen,

I would suggest the followings:

1) It is highly recommended that you first need to know where all the RGB bits are going from the

     TFP401A input -> TFP401A output-> DS90C387A input -> DS90C387A LVDS output -> LVDS RX input of flat panel. Trace all RGB bits on a paper was what I did.

2) Obtain the spec for the LVDS input flat panel (bare panel) you will be working on. You need to know the LVDS color bit mapping. Base on the LVDS color bit mapping     of the flat   panel, you need to connect TFP401A output pins to DS90C387A input pins accordingly.

3) TFP401A can output two 24bit RGB pixels from 48 output pins (dual pixel output) OR one 24bit RGB pixel from 24 output pins (single pixel output).  My DVI-LVDS board allowed me to configure DS90C387A to accept either "dual pixel" or " single pixel" from TFP401A. However, I had some display issues on the LG 23" 1920x1080 LCD monitor when TFP401A was in "dual pixel output " mode, and DS90C387A in " dual pixel in-dual pixel out" mode. The moment I configured TFP401A in " single pixel output" mode, and DS90C387A to " single-to-dual mode", the LG 23" worked just fine.

4) Since it is DVI interface, you need to "cheat" the graphics source to generate the correct display timing for the flat panel. Meaning, you will need to do some EDID editing. Since the LG 23" was a LCD monitor, I found a EDID reading tool on internet that allowed me to read the EDID off the LG monitor. I then copied this set of EDID to the EEPROM on my DVI-LVDS board. By doing so, the graphics source would generate the correct display timing for the LG 23" flat panel.

Good Luck!

Peter

Peter,

thanks for your detailed answer. At the moment I try to find out the lvds configuration of my panel.

You talked about a programm which can read out EDID from EEPROM. Do you read out with direct connection to that EEPROM like I2C or just by connecting the panel on a PC?

If you have some links/schematics you could share (j.h.duerrwang@arcor.de) with me, I will be grateful for that.

Greetings

Juergen

Hi there,

This is my first post on the TI forums. I've found a lot of very useful information from very bright individuals on these forums so I'm hoping someone can give me some help on a situation similar to Bernie's.

I'm trying to interface HDMI to LVDS. I am aware of a two chip solution to this using the TFP401A with DS90C387A.

However, the TFP401A doesn't seem to be able to decode HDCP. I found that the TFP501 is HDCP compatible so it will be able to decode the input before it is sent to the DS90C387A (is this correct?).

I haven't been able to find any stock of the TFP501. Is there an alternative to achieve the same result?

I am looking for something that can handle dual pixel.

Please correct me if I have used any incorrect terminology. I've only started reading into these topics over the past 2 days and I would like to learn the correct terminology.

Thank you for your help :)

Ibrahim

Hello,

The TFP401A does not have HDCP support.

The TFP501 is sold only to HDCP-members due to legal requirements, there are some test keys to test the HDCP capabilities but again it is only sold to approved members.

we need to understand your application in order to tell if the TFP401+DS90C387a will work (pixel clock, bits per pixel, frames per second, panel requirements, etc)

Regards.

Hi Elias,

Thanks for your reply. Our company is just a start-up so we have not applied to become HDMI adopters as of yet. We looked into the membership prices and we may be able to afford membership in the near future, but not now. It seems like we will have to stick with the non-HDCP option.

Our application requires us to push images to two screens over one HDMI cable. Some manipulation at the receiver end will allocate frames to each screen appropriately.

Ideally, we are looking to support a 60Hz framerate, with 24 bit colour depth, and a clock rate of around 70MHz.

It looks like the TFP401A and TFP501 share the same pinout, so I'm assuming they can be swapped out at a later date without needing modifications to the design.

Cheers,

Ibrahim

Hello Ibrahim,

The TFP401A is not pin to pin compatible with the TFP501, however we have the TFP403 which is pin to pin compatible with the TFP501.

Can you provide a block diagram of your application?

Regards.