DLPS021 September   2019

PRODUCTION DATA.

1. Features
2. Applications
3. Description
1.     Device Images
4. Revision History
5. Pin Configuration and Functions
6. Specifications
7. Detailed Description
8. Application and Implementation
1. 8.1 Application Information
2. 8.2 Typical Application
3. 8.3 Temperature Sensor Diode
9. Power Supply Recommendations
10. 10Layout
1. 10.1 Layout Guidelines
2. 10.2 Layout Example
1. 10.2.1 Layers
2. 10.2.2 Impedance Requirements
3. 10.2.3 Trace Width, Spacing
11. 11Device and Documentation Support
12. 12Mechanical, Packaging, and Orderable Information

• FQN|250

### 7.6 Micromirror Array Temperature Calculation

Micromirror array temperature cannot be measured directly, therefore it must be computed analytically from measurement points on the outside of the package, the package thermal resistance, the electrical power, and the illumination heat load. The relationship between array temperature and the reference ceramic temperature (thermal test TP1 in Figure 10) is provided by the following equations:

TARRAY = TCERAMIC + (QARRAY × RARRAY-TO-CERAMIC)
QARRAY = QELECTRICAL + QILLUMINATION

where

• TARRAY = Computed array temperature (°C)
• TCERAMIC = Measured ceramic temperature (°C) (TP1 location)
• RARRAY-TO-CERAMIC = Thermal resistance of package specified in Thermal Information from array to ceramic TP1 (°C/Watt)
• QARRAY = Total (electrical + absorbed) DMD power on the array (Watts)
• QELECTRICAL = Nominal electrical power
• QILLUMINATION = (CL2W × SL)
• CL2W = Conversion constant for screen lumens to power on DMD (Watts/Lumen)
• SL = Measured screen Lumens

The electrical power dissipation of the DMD is variable and depends on the voltages, data rates, and operating frequencies. A nominal electrical power dissipation to use when calculating array temperature is 1.3 W. The absorbed power from the illumination source is variable and depends on the operating state of the micromirrors and the intensity of the light source. The equations shown above are valid for a 1-chip DMD system with projection efficiency from the DMD to the screen of 87%.

The conversion constant CL2W is calculated to be 0.00266 W/lm based on array characteristics. It assumes a spectral efficiency of 300 lumens/Watt for the projected light and illumination distribution of 83.7% on the active array, and 16.3% on the array border.

A sample calculation for a typical projection application is as follows:

SL = 1500 lm (measured)
TCERAMIC = 55.0°C (measured)
CL2W = 0.00266 W/lm
QELECTRICAL = 1.3 W
QARRAY = 1.3 W + (0.00266 W/lm × 1500 lm) = 5.29 W
TARRAY = 55.0°C + (5.29 W × 1.2°C/W) = 61.35°C