An energy efficient high-speed digital LED driver for visible light communications

In this paper an energy efficient light emitting diode (LED) driver circuit for visible light communications (VLC) and results from the electrical and optical characterization are presented. A current steering digital to analogue converter (DAC) based LED driver circuit supporting 4-channels with an 8-bit resolution is realized in a 0.18 µm complimentary metal oxide semiconductor (CMOS) technology. Each channel delivers a full-scale current of 255 mA and achieves up to 67% electrical efficiency when driving 250 MS/s orthogonal frequency division multiplexing (OFDM) signals. Optical differential drive capability is demonstrated by using two output branches of a single channel to drive two different LEDs with an SNR improvement (>5 dB). The chip is also capable of full digital control of color shift keying (CSK) using multi-color LEDs enabling lighting color-temperature adjustment, dimming and multiple-input and multiple-output (MIMO) optical communications and these aspects will be the subject of future research.