IC-HK_1 Datasheet, PDF (7/13 Pages) IC-Haus GmbH – 155MHz LASER SWITCH

iC-HK
155MHz LASER SWITCH
Rev 21.11.01, Page 7/13
iC-WK controls the mean value of the monitor current.
This thus has to be calculated from the high and low
level and the duty cycle of the monitor current as
follows:
Im_av = Im_hi × t_hi / T + Im_lo × t_lo / T
For a current ratio of k = Im_hi / Im_lo it follows that
Im_av = Im_lo × (t_lo + k t_hi) / T
or
Im_av = Im_hi / k × (t_lo + k t_hi) / T
Fig. 16: Pulse pattern for Example 5 -
power control for pulse and bias current
Resistor RM is calculated as
RM = 500mV / Im_av
The optimum operating point for iC-WK is if the voltage across CI and GND is approximately 1.7V. With the aid
of resistor RGND or diode DGND the ground potential of iC-WK can thus be raised with respect to the system
ground. RGND is typically set to
RGND = (V(CI) - 1.7V) / 45mA
Diode DGND should be selected so that the forward voltage V_fw(DGND) is
V_fw(DGND) = V(CI) - 1.7V