iC-GE is a PWM driver for inductive loads, such as relay coils, solenoid valves and other inductive loads.
The setpoints for the coil’s energising and hold current are preset by means of external resistors RACT and RHOLD. These currents can be set in a range from 100 mA to 1 A. The iC-GE intrinsically switches from energising to hold mode after 50 ms provided that the set energising current has been reached. A capacitor at TACT prolongs the time before the switch to hold mode occurs.
The changeover between energising and hold modes is suitable for typical relay drives which require a powerful initial energising current which can then be reduced after closing the air gap in a magnetic circuit. The quadratic dependence on the current intensity means that cutting the current by halv reduces the power dissipation by ca. 75%.
Using PWM the output current is controlled to the values set at RACT and RHOLD. The internal fly back diode maintains the current during the switching pauses. The switching frequency of ca. 80 kHz is provided by the internal oscillator. Varying this frequency between 70 kHz and 90 kHz reduces the EMI.
The device is shutdown by a Low signal at input EN or the removal of the power supply; the current reduction in the coil is supported by the changeover of the free-wheeling circuit. The Zener diode now active permits higher free-wheeling voltages and thus a quicker demagnetising of the coil.
