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DLP Pattern When the Device is Switched Off

Raymond Santoso
Prodigy 120 points
Other Parts Discussed in Thread: DLPC300

Hello everyone,

Does anybody knows what is the state of the mirrors after the device is switched off? For example, when I loaded the 'Fine Checkered Board' pattern under the Test Pattern, and then switch off the device, I can see by looking at the chip that the checkered board pattern still remains. However, when I test it with a low-power laser, the reflection off the chip is definitely different. Could anyone explain to me the state of the mirrors when the device is off? Are they washed into the parked (0 degree) state?

Thank you very much!

  • 0
    TI__Mastermind 30875 points

    Hello Raymond,

    The state of the mirrors should be PARK state provided proper system-power on/off sequence is followed.

    The DLPC300 takes care of properly powering down the DLP3000 DMD power-down sequence is followed. 

    This is explained in the DLPC300 controller data sheet http://www.ti.com/lit/ds/dlps023b/dlps023b.pdf under section System Power-Up/Down Sequence

    The suggested powering down -

    1. DLPC300 PARKn or B8 I/O must be de-asserted, then DLPC300 would de-assert DMD_PWR_EN or K18 I/O in about  ~ 500 +/ - 5 us. 

    2. Then it is very important the core-voltage VCC1.8 of DLPC300 must be stable for atleast 100ms 

    this will ensure the DMD is powered down in proper state.

    Now, not following the procedure would cause DMD to mirrors remain in the last memory load position and would show image imprints, this is something called as Hinge-memory there is article explaining this behaviour http://focus.ti.com/download/dlpdmd/155_IRPS2003_DMDHingeMemoryLifetime_Sontheimer_Mehrl_5C3.pdf

    Feel free to comment back if anything not clear.

    Regards,

    Sanjeev

  • 0 in reply to Sanjeev
    Prodigy 120 points

    Dear Sanjeev,

    Thank you very much for the quick and detailed explanation.

    For my application, I am powering the Lightcrafter module very simply by having a 5V Lab power supply connected to the power socket plug. As such, the way I switch off the device is simply by switching off the connection between the DLP board and the power supply. Two things I would like to ask:

    1. Given the way I power the system, is there a way to power down 'correctly' as you suggested? From my limited understanding, it seems that I need to stabilize the voltage supply below a certain level for several 500 us before switching off completely. Could you please describe this in more detail?

    2. If I continue to switch off the device just by hand switching the power supply, then as you mentioned there would be some image imprints. From the manual, it seems that doing this would not cause a damage to the device, is this true?

    Thanks so much for the reply!

    Raymond

  • 0 in reply to Raymond Santoso
    TI__Mastermind 30875 points

    Hello Raymond,

    #1. You can use the push-button marked below first before removing the main power supply. The MSP430 on the system would ensure sending proper commands to DLPC300 to set DLP3000 in proper PARK state.

    #2. yes, it is true, there won't be any damage to the device. For the device reliability and longevity it is suggested to power off the device systematically. 

    Regards,

    Sanjeev

  • 0 in reply to Sanjeev
    Prodigy 120 points

    Hey Sanjeev,

    Thanks so much for the suggestion. I will try this the next time I use the device.

    Regards,

    Raymond