DLP9500: Thermal Measurements, Dissipation and Incident Light

Lucas,

1. Are there guidelines or designs for how to add passive or active cooling units to this package? I have been looking around without no success but I always see posts talking about the "Design Search Tool" or the "Discovery Extranet" which I couldn't find.

The references are to older resources.  Please look at:  https://www.ti.com/lit/pdf/dlpa067 as a starting reference.  The website has undergone some redesign.  Try starting here if you need design assistance:  https://www.ti.com/design-resources/embedded-development/dlp-chip/display-and-projection.html#production 

2. Are there any recommendations on how to put the sensors at the temperature test points? Which sensors should I use?

Typically we use thermocouples and make a very small channel in the heatsink for the wires and embed the thermocouple and wires in epoxy.  You can use other sensors as well.

3. And my last question is about the incident light. Is there any issue I should be worried about if I illuminate the DMD from the opposite side? I would suppose the only change is that the On and Off states are swapped. See the next picture for an illustration.

It is possible to do this.  You can even use the non-inverted data and turn on "complement data" to turn all 1's -> 0's and 0's -> 1's.  There is one caveat.  The border pixels are fixed regardless of incoming data.  This means that instead of a dark border there will be a bright border.  If you can afford the pixels, you can create your own border, but will sacrifice some rows top and bottom and columns left and right.  Also the dark shield area is offset to accommodate the incident light as shown in the data sheet diagram, so depending on how steep your incident illumination is, a few rows on the bottom and a few columns on the left may be occluded.

Have you considered rotating the DMD in your design so that DMD is oriented to the incident light as described in the data sheet?  Is there a compelling reason to no do so?

I hope this helps.

Fizix

Hello Lucas,

I have colored the diagram a bit so I can refer to the different parts:

The cyan rectangle is typically a small sheet of thermal pad material.  The green slug should contact the back of the DMD with the cyan rectangle as the thermal interface.  I have made an exaggerated drawing of the type of thing we do on the front side of the green slug (on the side facing the cyan material) to embed a thermocouple:

We make this a small channel in the aluminum slug big enough for the wire and make the center a small "divot" big enough for the thermocouple welded ball and then epoxy it all in place.  Just make sure that it is flat when you are done for interfacing to the thermal pad of the DMD.  There should be enough room for the lead to come out beside the green slug and through the opening in the yellow spring and past the pink plate.

Regarding the pink plate, you may certainly use thermal paste or a pad between the green slug and the pink plate.

You can also replace the pink plate with heat sink with fins/pins so long as it is relatively light weight.  The requirement is that the footprint  on the side facing the yellow spring/green slug is the same, since this is the part that puts pressure on the back side of the yellow spring to provide the correct mechanical pressure on the DMD thermal interface.

All of this assumes you are using this particular mounting style.  The mechanical forces are specified in the data sheet for the DMD if you need to have a third party design a more robust heat sink.

I hope this helps.

Fizix