Calculating Global Overlap Windows in Sequential Row Readout Image Sensors
Calculate global overlap by subtracting array readout time from total exposure; fire external illumination within this window to emulate global shuttering.
Optoisolator Slew
Signal Transition
Rate of change in the output voltage of a galvanically isolated coupling device when the input state is toggled determines the maximum frequency at which data can be reliably transmitted. The optoisolator slew depends on the internal capacitance of the phototransistor or photodiode and the speed of the light emitting element. Slow transitions limit the bandwidth and introduce timing errors in digital communication.
Miller Effect
Feedback capacitance between the base and collector of the internal transistor slows down the voltage swing during switching. High values of optoisolator slew are achieved by using active drive circuits or logic output stages that bypass the slow response of a standard transistor. Choosing the correct load resistor is essential for optimizing this speed.
Delay Distortion
Differences in the time it takes for the signal to rise versus the time it takes for the signal to fall can cause pulse width distortion. This imbalance is closely linked to the optoisolator slew and can lead to data corruption in high speed serial protocols. System designers must account for these delays when setting the clock rate.
Thermal Impact
Changes in ambient temperature alter the gain and capacitance of the internal components. These variations cause the optoisolator slew to drift which can affect the timing margin of the entire circuit.