Panel source driver circuits include a first data register and a second data register. A common data demultiplexer coupled to the first and second data registers is configured to provide control data from a first input of the demultiplexer to the first data register and control data from a second input of the demultiplexer to the second data register in a first operation mode and to provide control data from the second input to the first data register and control data from the first input to the second register in a second operation mode responsive to an operation mode select signal. A first decoder is coupled to an output of the first data register that is configured to select one of a plurality of first voltages having different levels responsive to the output of the first data register and to output the selected first voltage. A second decoder is coupled to an output of the second data register that is configured to select one of a plurality of second voltages having different levels in response to the output of the second data register and to output the selected second voltage.