DLP670S: DLPLCR67EVM voltage issues

Hi Brian,

May I clarify that you are using a ground point on the DLPC900? I am making sure you did not mistype this. You should be measuring with respect to one of the ground points from the DLP670S EVM instead. Possible grounds you may use are found on test points TP8 and TP9, as found in the schematic.

May I also know what values you were reading off? How far off were they from the actual specifications?

I assume you are using the DLPC900 reference software/GUI as well. May you show which firmware version you are using and what the firmware tag is? This should be displayed near the top in the left sidebar of the GUI. Knowing this can help me eliminate what could be wrong with the lack of patterns showing on the DMD after the DLPLCRCC900DEVM powers on.

Also, have you attempted to try the pattern on-the-fly mode and pre-stored pattern modes? What results have you gotten from that? Does video mode actually display proper video and eventually lock to the external source you are using? There should be a checked status box for this under the left-hand stats flag menu.

Are there any other status flags that are checked when going through and verifying these different modes?

Regards,
Michael Ly

Hi, 

I followed your suggestion and tested the voltages between the DLP670S EVM ground (TP8, TP9) and the three test points VOFFSET, VRESET, VBIAS (TP3, TP5, TP6). The measured corresponding voltages are 2.558V, 0V, 0V, which doesn't match the spec sheet (10V, -14V, 18V). I think the DLP670S EVM board is not properly powered. 

I connected everything following the instructions in the DLP900 EVM board manual. I also tried rescrewing the flex cables that connect the DLP900 and DLP670S board, but to no avail. According to the DLP670S manual the board is powered by the DLP900 board through the cable, so I shouldn't need to connect anything else, right?

On a side note, I have two boards that uses the DLPC900 LightCrafter software (the current DLP670S DMD and a DLP6750Q1EVM phase SLM, both use the same chipset DLP670S). Would I be able to control two boards (i.e. display patterns using Video Pattern Mode) using the same computer?

Thanks!

Also, I probed the pins of TPS65145 chip on the DLP670S EVM (p.4 of the schematic), and pin 24 (seems like the enable signal?) is 0V. Is this normal? Other pins I tested include pin 9 (which reads 3.3V) and pin 4 (also 3.3V). 

Hi Brian,

Brian Chao said:

I followed your suggestion and tested the voltages between the DLP670S EVM ground (TP8, TP9) and the three test points VOFFSET, VRESET, VBIAS (TP3, TP5, TP6). The measured corresponding voltages are 2.558V, 0V, 0V, which doesn't match the spec sheet (10V, -14V, 18V). I think the DLP670S EVM board is not properly powered. 

I have gone and tested these values with a multimeter using VDC setting and have the values below. I find that using TP30 as a ground point is much easier than using TP8 or TP9 for probing the signals on the back of the board.

1. TP3 (VOFFSET) = +9.94 V
2. TP5 (VRESET)   = -14.01 V
3. TP6 (VBIAS)       = +18.02 V

The values lineup with the nominal values given in the datasheet.

I see that you have tested LEDs. May I ask about the two LEDs, D9 and D7? They should be blinking if the board has properly configured.

Brian Chao said:

I connected everything following the instructions in the DLP900 EVM board manual. I also tried rescrewing the flex cables that connect the DLP900 and DLP670S board, but to no avail. According to the DLP670S manual the board is powered by the DLP900 board through the cable, so I shouldn't need to connect anything else, right?

What you have described for hardware set up sounds correct. May I get a couple of pictures just in case there is something neither of us have checked yet?

Brian Chao said:

On a side note, I have two boards that uses the DLPC900 LightCrafter software (the current DLP670S DMD and a DLP6750Q1EVM phase SLM, both use the same chipset DLP670S).

I would not recommend using the DLP6750Q1EVM for this and would stick to the DLPLCR67EVM SLM you have been using.

Brian Chao said:

Would I be able to control two boards (i.e. display patterns using Video Pattern Mode) using the same computer?

I cannot say with 100% certainty that the GUI can control two compatible DMD EVMs at the same time, but in my experience, the GUI will only lock onto one DMD EVM at a time, even after you create a new instance of the GUI. Any new instance of the GUI, for me, has always shown "Disconnected" as far as I recall.

May I also know which firmware version you are using? Please upload the newest released version, 6.2.0 and let me know if you are able to properly program the DLP670S EVM. Please select both primary and secondary at the same time when uploaded. You can read how to do this in the user's guide for the dual-ASIC EVM you have been using.
Here is the link to the DLPR900 configuration and support software: https://www.ti.com/tool/DLPLCRC900DEVM#order-start-development

Regards,
Michael Ly

Hi Brian,

Sorry I forgot to answer this in my previous reply. This is an active high signal, so it is expected to be 0V. There is a pulldown resistor (R16) that pulls this signal low when not in use.

This signal is generated from the DLP670S DMD Pin H3 and is called DMD_EN_OFFSET (Page 6).
DMD_EN_OFFSET goes to a level shifter (U7, Page 5) that converts the 1.8 V signal from the DMD to a 3.3 V signal (EN_OFFSET) that goes to the TPS65145 (U2, Page 4).

As for Pin 4, this is directly tied to a 3.3V line. The same 3.3 Volts is also applied to Pin 9.

I hope this helps explain what is going on here. For more information, you can see section 9 of the DLP670S datasheet. This has a figure of the DMD power supply requirements and shows how EN_OFFSET is used.

Regards,
Michael Ly

Hi Brian,

Do you have any updates on the pictures and measurements? Were you able to get the DLP670s EVM properly working?

Please let me know.

Best,
Michael Ly