Other Parts Discussed in Thread: SN74AXC8T245
TXS0108-Problem.pdfDear Sirs,
We use a FPGA Evaluation Board with onboard TXS0108 Level shifters for the IO Ports. Two IO Bits are used for switching on a DC fan via an ULN2803A open collector Driver. (refer to schematic)
The symptom is that setting a logic one on the FPGA Output should send this from A side of TXS0108 to the B-side. But the B side output got stuck at app. 0.9V and the fan did not start.
We could fix this problem by adding a 10k pullup resistor on the B-side to VCC3V3. But we do not understand why this resistor is necessary, because there are pullups internal to the TXS0108.
The lenght of the PCB trace from TXS output to ULN Input is about 2".
