DLPS284 December   2025 DLP3940S-Q1

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  Storage Conditions
    3. 5.3  ESD Ratings
    4. 5.4  Recommended Operating Conditions
    5.     11
    6. 5.5  Thermal Information
    7. 5.6  Electrical Characteristics
    8. 5.7  Switching Characteristics
    9. 5.8  Timing Requirements
    10.     16
    11. 5.9  System Mounting Interface Loads
    12.     18
    13. 5.10 Micromirror Array Physical Characteristics
    14.     20
    15. 5.11 Micromirror Array Optical Characteristics
    16. 5.12 Window Characteristics
    17. 5.13 Chipset Component Usage Specification
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 SubLVDS Data Interface
      2. 6.3.2 Low Speed Interface for Control
      3. 6.3.3 Power Interface
      4. 6.3.4 Timing
    4. 6.4 Device Functional Modes
    5. 6.5 Optical Interface and System Image Quality Considerations
      1. 6.5.1 Numerical Aperture and Stray Light Control
      2. 6.5.2 Pupil Match
      3. 6.5.3 Illumination Overfill
    6. 6.6 Micromirror Array Temperature Calculation
      1. 6.6.1 Monitoring Array Temperature Using the Temperature Sense Diode
    7. 6.7 Micromirror Power Density Calculation
    8. 6.8 Window Aperture Illumination Overfill Calculation
    9. 6.9 Micromirror Landed-On/Landed-Off Duty Cycle
      1. 6.9.1 Definition of Micromirror Landed-On/Landed-Off Duty Cycle
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Application Overview
      2. 7.2.2 Input Image Resolution
      3. 7.2.3 Reference Design
      4. 7.2.4 Application Mission Profile Consideration
      5. 7.2.5 Design Requirements
      6. 7.2.6 Detailed Design Procedure
    3. 7.3 Temperature Sensing
      1. 7.3.1 Temperature Sensing Diode
        1. 7.3.1.1 Temperature Sense Diode Theory
  9. 8 Power Supply Recommendations
    1. 8.1 DMD Power Supply Power-Up Procedure
    2. 8.2 DMD Power Supply Power-Down Procedure
    3. 8.3 DMD Power Supply Sequencing Requirements
  10. 9 Layout
    1. 9.1 Layout Guidelines
  11. 10Device and Documentation Support
    1. 10.1 Third-Party Products Disclaimer
    2. 10.2 Device Support
      1. 10.2.1 Device Nomenclature
      2. 10.2.2 Device Markings
    3. 10.3 Documentation Support
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

6.6 Micromirror Array Temperature Calculation

DLP3940S-Q1 DMD Thermal Test Points Figure 6-2 DMD Thermal Test Points

The active array temperature can be computed analytically from the thermal measurement point on the outside of the package, the package thermal resistance, the electrical power, and the illumination heat load. The following equations provide the relationship between the array temperature and the reference ceramic temperature (TP1) in Figure 6-2:

Equation 1. TARRAY = TCERAMIC + (QARRAY × RARRAY–TO–CERAMIC)
Equation 2. QILLUMINATION=QINCIDENT×DMD Absorption Constant
Equation 3. QARRAY=QELECTRICAL+QILLUMINATION

where

  • TARRAY = computed array temperature (°C)
  • TCERAMIC = measured ceramic temperature at the TP1 location in Figure 6-2 (°C)
  • RARRAY–TO–CERAMIC = DMD package thermal resistance from array to thermal test point TP1 (°C/W)
  • QARRAY = total power (electrical plus absorbed) on the DMD array (W)
  • QELECTRICAL = nominal electrical power dissipation by the DMD (W)
  • QILLUMINATION = absorbed illumination heat load (W)
  • QINCIDENT = incident power on the DMD (W)

The DMD absorption constant is a function of illumination distribution on the active array and the array border, angle of incidence (AOI), f number of the system, and operating state of the mirrors. The absorption constant is higher in the OFF state than in the ON state. Equations to calculate the absorption constant are provided for both ON and OFF mirror states. They assume an AOI of 29 degrees, an f/2.0 system, and they account for the distribution of light on the active array, POM, and array border.

Equation 4. DMD Absorption Constant (OFF state) = 1.004 – 0.005235 × (% of light on ActiveArray + POM)
Equation 5. DMD Absorption Constant (ON state) = 1.004 – 0.007776 × (% of light on ActiveArray + POM)

Electrical power dissipation of the DMD is variable and depends on the voltages, data rates, and operating frequencies.

The following sample calculations assume 10% of the total incident light falls outside of the active array and POM, and the mirrors are in the OFF state.

  1. TCERAMIC = 50°C (measured)
  2. QINCIDENT = 10W (measured)
  3. DMD Absorption Constant = 1.004 – 0.005235 × 90 = 0.533
  4. QELECTRICAL = 0.5W
  5. RARRAY–TO–CERAMIC = 2.6°C/W
  6. QARRAY = 0.5W + (0.533 x 10 W) = 5.83W
  7. TARRAY = 50°C × (5.83W × 2.6°C/W) = 65.2°C

When designing the DMD heatsink solution, the package thermal resistance from array to reference ceramic temperature (thermocouple location TP1 can be used to determine the temperature rise through the package as given by the following equations:

Equation 6. TARRAY-TO-CERAMIC = QARRAY × RARRAY–TO–CERAMIC