16 | 50
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Fig. 3: Relaxation time vs. temperature
3.6.
ITO Heater
Each DBSD has three ITO heaters dedicated to heating (one internal and two on the external layer).
Table 8: ITO heater resistance
Parameter
Value
Single ITO heater resistance
250
Ω to 325
Ω/□ (Ω/sq) (310
±20%)
Sheet resistance is a special case of resistivity for a uniform sheet thickness. Ohms-per-
square (Ω/□ or Ω/sq)
is the unit of measurement when measuring the resistance of a thin film of material using the four-point probe
technique. It is equal to the resistance between two electrodes on opposite sides of a theoretical square.
The size of the square is unimportant. It is dimensionally equal to an ohm but is exclusively used for sheet
resistance.
3.7.
Overdrive
The relaxation time can be accelerated by br
iefly applying an “overdrive” voltage beyond the one that must
be applied before going to the target voltage. The overdrive duration can be between 10 µs and 20 ms
depending on the temperature and the voltage difference between the previous and target voltages. This
overdrive is applied only during a slow transition time, from high to low-voltage drive.
Avg
mV
+1 V
+20 V
Initial state
Overdrive
Required drive
-20 V
-1 V
Fig. 4: Overdrive waveform, from high to low voltage
