The active array temperature can be computed analytically
from the temperature sense diode measurement, the thermal resistance from array
to diode, the electrical power, and the illumination heat load. The relationship
between array temperature and the temperature sense diode is provided by the
following equations:
Equation 7. TARRAY =
TDIODE + (QARRAY ×
RARRAY–TO–DIODE)
Equation 8. QILLUMINATION =
(QINCIDENT × DMD Absorption Constant)
Equation 9. QARRAY =
QELECTRICAL + QILLUMINATION
where
- TARRAY = computed
array temperature (°C)
- TDIODE = measured
temperature sense diode temperature (°C)
- RARRAY–TO–DIODE =
package thermal resistance from array to diode (°C/W)
- QARRAY = total power,
electrical plus absorbed, on the DMD array (W)
Refer to Section 6.6
for details.
- QELECTRICAL = nominal
electrical power dissipation by the DMD (W)
- QILLUMINATION =
absorbed illumination heat load (W)
- QINCIDENT = incident
power on the DMD (W)
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.
- TDIODE = 55°C
- QINCIDENT = 10W
(measured)
- DMD Absorption Constant = 1.004 –
0.005235 × 90 = 0.533
- QELECTRICAL =
0.5W
- RARRAY–TO–DIODE =
0.1°C/W
- QARRAY = 0.5W + (0.533
× 10W) = 5.83W
- TARRAY = 55°C + (5.83W
× 0.1°C/W) = 55.6°C