Why does TLD1315EL open load detection fail when output channels are connected together?
Double fault feature is implemented in TLD1315EL which prevents incorrect open load (OL) fault detection during supply voltage drops.
In an application where all three TLD1315EL output channels are externally merged together to drive the same LED load, the double fault feature acts avoiding the OL fault detection via ST pin. Therefore, the OL detection fails.
This feature can not be deactivated so it is not recommended to use TLD1315EL with its output channels merged together.
See https://www.infineon.com/cms/en/product/power/lighting-ics/litix-automotive-led-driver-ic/litix-basi... for the datasheet and application note.