PBL38085

PBL 380 85 is a monolithic integrated circuit for supplying power to an EL (electroluminicent) lamp. This is intended to replace the LCD background illumination system in battery powered handheld equipment with a low power EL- lamp. Especially suitable for mobile phones where current saving is highly important, as background illumination for both LCD and keyboard. Output voltage max. 190V, min. 170V at max. 2mA constant current charge / discharge of the EL- lamp. Application dependent parameters such as charge / discharge current are set by an external resistor. Two control signals are needed one for the switcher and one for the lamp.The output voltage is set under 170V by the duty cycle and the switching frequency of the control signal, over 170V by an amplitude limiter that switches the switcher off. The switching frequency is app. 50 kHz. The light intensity is controlled by the dutycycle of the switcher control signal. The lamp control signal is divided by two by the circuit. The wave form of the output AC-signal is either triangular or trapezoid depending of the capacitance of the EL-lamp, charge /  discharge current and frequency of the lamp control signal.The triangular or trapezoid wave form of the EL-lamp driving voltage and the high switching frequency minimizes audible noise from the lamp and also reduces upcoming electrical noise and harmonics.