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Can TXB0108 operate with VccA = VccB?

MikeH
Guru 15580 points
Other Parts Discussed in Thread: TXB0108

I am trying to design a voltage translator option to drive an +5V LCD with a 3.3V MSP microprocessor. However, I want to have the option of also using a 3.3v LCD. So can I use the TXB0108 with both VccA and VccB tied to the same voltage (3.3v)?

  • 0
    Intellectual 840 points

    From experience in using buffers ( some bad, some good  ) and reading the data on teh TXB0108 " VCCA should not exceed VCCB " which means you can ' cheat ' with resistors so that Vcca is always slightly lower.  Good power management would mean a simple switch for power to either have Vccb after something like 7805 regulator for position 1 and 10k tap to 1Meg to ground ( or some other resistor network so you have 1% less ) for power at Vccb and the lower at Vcca.  I highly recommend fuse protection for both as well as doubble throw so you can physically disconnect Vcca when it is not 5V Vccb.  Bad experiences in not paying attention to the disconnect had a few items go up in smoke and as it was an LPT interface, have a few ICs go on the motherboard too.  The main point ( besides disconnecting Vcca when using the 5V for Vccb ) is to make sure Vcca is always lower than Vccb and not on the same rail.

    Hope this points you in the direction you were looking for,

    Eric