The LED Open Detection (LOD) function detects faults caused by an open circuit in any LED, or a short from OUTn to VLED with low impedance. LOD was realized by comparing the OUTn voltage to the LOD detection threshold voltage level set by LODVTH_R/LODVTH_G/LODVTH_B (see FC3 for more details). If the OUTn voltage is higher than the programmed voltage, the corresponding output LOD bit is set to 1 to indicate an open LED. Otherwise, the output of that LOD bit is 0. LOD data output by the detection circuit are valid only during the OUTn turning on period.

Figure 8-5 shows the equivalent circuit of LED open detection.

Figure 8-5 LED Open Detection Circuit

The LED open detection function records the position of the open LED, which contains the scan line number and relevant channel number. The scan line order is stored in LOD_LINE_WARN register (for more details see FC12), and the channel number is latched into the internal 48-bit LOD data register for more details see FC14) at the end of each segment. Figure 8-6 shows the bit arrangement of the LOD data register.

Figure 8-6 Bit Arrangement in LOD Data Register