What is the meaning of input voltage range for the WLED boost regulator specified in the datasheet as 2.7-5.8 V?. As an ordinary boost WLED regulator it has SW and FB pins rated at 44V, ISINK pins rated at 20V and ISET rated at 7V. To what part of the WLED boost regulator 2.7-5.8 V limitation is applied? To the internal power circuit? If so then what is in this spec for the end user?
The question arises since I am contemplating committing to a project with AM335x being powered from a 24VDC rail. A buck converter at the input will bring the 24VDC input voltage to 3.3VDC to power TPS65217 and additional circuitry (eMMC, WiLink Wi-Fi+Bluetooth module, 2 uSB ports using TPS2505, 3G module, 8.4'' LCD screen, etc).
The problem is with the LCD backlight circuit. It has 2 x 100 mA strings of 10 WLEDs. Bringing 75 mA more WLED current additionally to 25 mA provided by TPS65217 is not a big deal (with some additional external circuit), but boosting 3.3VDC back isn't an option due to TPS65217's switching current limitation. The idea is to apply 24VDC directly to the inductor at the WLED regulator's input. Also the higher input voltage will decrease the converter's duty factor and bring its switching current back within the range specified. Therefore there is a question - since the voltage applied to the inductor is obviously the input voltage for the WLED boost regulator then what is the datasheet's input voltage range for?