Hi...can you tell me a bit more about your application? If I understand correctly, you're using a USB 8541 but you're only able to read an output of 3.8V, both from the digital output ports and from the 5V source built into the device, is this correct?
As per my research, the external +5 V is not a true 5 V signal. This is VUSB taken through a current limiting circuit so it cannot be considered true +5 V. It may be that your USB is not outputting the full 5V that you desire.
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