DLPC3433: When the temperature is higher than 60’C, the noisy screen happens.

Hi Chai Wei Yu, 

Thank you for your post and interest in the DLP3010 chipset! 

If you can able to display test patterns with seeing the noisy image, we can eliminate an issue with the sub-LVDS interface between the controller and the DMD. The controller feeds test patterns and external video content to the DMD using the same protocol. I agree with you that this problem is post likely due to the MIPI interface. 

Also, I noticed your image has vertical lines down the screen. This is a fail mode experienced by the DMD when the power down sequence doesn't have enough time to complete (wall power removed unexpectedly) or when the DMD pins have a loose connection. To prevent this from happening on other devices, please ensure the power down is executed properly with enough time and that the DMD has a good connection to the PCB.  

I have not seen this fail mode before, but it looks like the front end processor is trying to have the DMD display multiple copies of the same image. Can you supply any additional information about the system you are using or the datasheet for your MIPI DSI processor?

Also, we you say the system is running at 60C, is that the temperature of the 3010 DMD or the temperature of the DLPC3433?

Thanks, 

Brandon 

Hi Brandon, 

1. Yes. I know the vertical lines due to power down sequence. It's solved. But, DMD can't recovered.  

2. Only heating DLPC3433 will cause this noisy screen. Other components are good even it's hot.

The bridge that I'm using is ANX7530. Here is its website. 

https://www.analogix.com/en/products/convertersbridges/anx7530

BR,

Chia Wei Yu

Yes, it looks like the front end processor is trying to have the DMD display multiple copies of the same image. 

But, I don't see multiple copies when I measure MIPI data. 

Hi Chai Wei Yu, 

I am glad to know that the power down sequence is resolved. Unfortunately the damage caused by that fail mode is permanent. I'd recommend getting a new DMD before testing for image quality or any of those tests. The current DMD will work for our debug efforts!

I just checked the DLPC3433 datasheet for the operating temperature and the specification states: TA Operating ambient temperature range(5) –30 85 °C TJ Operating junction temperature –30 105 °C. Is the 60C number you mentioned the junction temperature or the ambient temperature? Even if the ambient temperature is within the -30C to 85C specification, the junction temperature may be out of spec.

When you run test patterns with the DLPC3433 controller at 60C, does the image display correctly? Also, are you able to display the images with the MIPI DSI without noise at lower temperatures? What is the resolution of the image you are trying to display?

Thanks, 

Brandon

Hi Brandon,

This DMD only work for debugging. 

60'C is measured on the top of DLPC3433.

When you run test patterns with the DLPC3433 controller at 60C, does the image display correctly?

=> Yes, it works correctly. And then, I use I2C to change back to the external video mode, it's still abnormal display.

Also, are you able to display the images with the MIPI DSI without noise at lower temperatures?

=> Yes. it works well at lower temperatures. I use cooler to touch DLPC3433, it changes to work correctly immediately. 

What is the resolution of the image you are trying to display?

=> 2560x720 image.

(2560x720 is the input of ANX7530. 1280x720 is the output of ANX7530 for each panel. Totally it drives 2 panels. My phone only can output 1280x720 image. And ANX7530 cut half image with half black to show on one panel and cut the other half image with half black to show on the other panel. If I use NB, it can output 2560x720 image. And, each panel can have whole 1280x720 image.)

Hello Chia,

Please take a look at the DSI debugging guide below. We have seen some temperature related sensitivity to the DSI interface. Could you confirm how you are testing the device over temperature? The EMI from a heat gun could actually cause the issues. Additionally, careful attention the the layout can also mitigate or eliminate problems over temperature. Could you confirm you followed the attached layout guidelines and the DLPC3433 guidelines for DSI layout?

Thanks,
Kyle

6378.DSI Setup and Debugging Guide v0.2.pdf

Hi Tyle,

1.      I used hair dryer and found the issue. But, it’s not easy to figure out which component cause the issue. So I used Hot melt adhesive to melt the plastic glue on the top of each component. And then, Only DLPC3433 is found temperature sensitive and cause the noisy screen.

2.      I’d like to share a video. In the beginning, the temperature is low and the display is good at external video mode. And then, DLPC3433 is heated by melted plastic glue and soon the noisy screen is happening. And then, the mode is changed to the test pattern mode. The checker board pattern is good and it approves sub-LVDS is good. And then, the mode is changed to external video mode. The noisy screen is still on the screen. Could you help to check if the noisy screen is same as the freeze image that you mentioned?

BR,

Chia Wei.

Hi 

Is there any update?

BR,

Chia Wei.

Hello Chia,

Could you confirm the image issue is caused by heat and not EMI from a hair dryer? A hair dryer will output lots of EMI which has been seen to cause this issue. If you have a thermal stream or temperature chamber that would be ideal.

Thanks,

Kyle 

Hi Kyle,

1. Sure. I'll arrange a temperature chamber to check it again. 

2. However, the bridge IC (ANX7530) output LP mode for the blanking of HSYNC and HBP during pixel lines.  

    The bit of related register only can set 1 to force LP mode and set 0 to enter LP mode automatically if the blanking is long enough.

    It can't set to keep HS mode during pixel lines.

    Do you think that it's ok?

3. It's easy to see the issue if THS-prepare + THS-zero is less than 465ns. So, I changed THS-prepare + THS-zero is less from 285ns to 650ns. It works for most of my PCBs.  Only the 2 PCBs are found out the issue. I'm not sure if this information can help you to find out the root cause. 

BR,

Wilbur.

(Continued my question)

Could you also help to define the temperature value that may casue the freezing screen? 

Hi Kyle,

Any update for my questions?

Hello Wilbur,

1. Any update on the temperature chamber test?
2. It is intended that LP mode is required during vertical blanking and vertical sync. LP mode is not supported between pixel lines (i.e. HS blanking must be used for horizontal blanking and horizontal sync). I do not know what (if any) implications may exist outside of this mode. 
3. Glad you fixed this timing. I do not know what may happen if out of spec.

I cannot determine an exact temperature that may cause this problem. On TI's internal hardware I have not been able to replicate the problem. Once everything is configured properly (software and layout) I expect you will be able to operate over the full temperature range.

Thanks,
Kyle 

Hi, Kyle,

Here is my update.

1.      I fine tune the MIPI timing. And, the issue is improved a lot but still can be seen on one eye, and it's ok on the other eye.  And then I remove the wires that are connect to scope on that eye, the noisy screen doesn’t happen on both eyes. But, I need to check more samples.

2.      However, the bridge IC (ANX7530) still outputs LP mode for the blanking of HSYNC and HBP during pixel lines. If HFP and the sum of HBP and HSYNC is not too big, it may keep HS during. Now I only have the input timing table like below.

May I know if there is a range for HFP, HSYNC and HBP? If so, I’d like to set a small number for them and check if it can keep HS mode during that period.

BR,

Wilbur.

Hello Wilbur,

Sorry for the delay. Please view page 23 of the DLPC3433 datasheet for supported porch and sync timings. Also any update on the temperature chamber test?

Thanks,
Kyle 

Hi Wilbur,

Any update on the temperature chamber?

Thanks,
Kyle