An optical sensor circuit comprises an optical sensor (DET) designed to provide a sensor signal indicative of light incident on the optical sensor (DET). A clock terminal (CLK) is used to receive a clocked control signal comprising high and low states. A controller unit (CU) is connected to the optical sensor (DET) and to the clock terminal (CLK). The controller unit (CU) is designed to process the sensor signal as a color signal (CTS) in a first mode if the clocked control signal is in high state, and process the sensor signal as an ambient light signal (ALS) in a second mode if the clocked control signal is in low state, and further designed to generate a driving signal (PWM) to drive a light emitting device (LED) to be connected at a control terminal (OUT). The driving signal (PWM) depends on the color and ambient light signal (CTS, ALS).