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Demultiplexing and boosting PWM signals

Dakota Roscoe
Prodigy 20 points
Other Parts Discussed in Thread: MUX506, CD40109B

I am trying to find the right part or parts to multiplex and boost the voltage of a signal being created by an FPGA.

The signal will output from the FPGA at 2.5V and is desired to be run at 10MHz. The frequency needs to be maintained as best as possible while also raising the voltage to ~8-10V.

The Demultiplexing is required as we do not have enough pins from the FPGA to drive as many signals as we need. A minimum of 1:4 demultiplexing is needed the more the better if possible. 

The original concept was to use an addressable latch that could latch to the input rail and use this as both however we realized that the VIH of the latch was around 6V to get a 10V output and that we would need to step up our input voltage to the latch. On top of this the latch was too slow as it was 8MHz max rate which would then be divided by 8 as that was the demultiplexing leaving us with 1MHz signal.

The goal is to use the FPGA and Latches to create a PWM signal for control of a different circuit.

Thank you in advance for the help. 

Edit: Realized the way I mentioned the PWM is wrong/confusing.This has been corrected.

Edit2: Fixed screw up multiplexing vs demultiplexing

  • 0
    TI__Mastermind 45575 points

    Dakota,

    You can use the switch selection tool on ti.com to search for devices that are 4:1, 8:1, 16:1 etc.  Almost all of them will support 10MHz signals.  I filtered below for 4:1, 8:1, and 16:1.  I also filtered for Vdd min >10 V so it will support your 10 V signal.  What do you think about using the MUX506?

    Next you will need to look for a level shifter or buffer to get your to 10V.  Maybe something like the CD40109B?

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    Prodigy 20 points

    Thank you Adam for the quick response. The level shifter looks like a potential candidate that could work. There were concerns however with using the level shifter straight from the source pins and preferred to use them after. As for the MUX I realize now that I used the wrong term when writing this. That is my fault, What I more so need is a DEMUX. Can I use the same tool you listed for that? I need something that is a 1:4 or 1:8 (input:output). I definitely conflicted my own statements in the post and I apologize for that.

    Another component of this problem is the need of the output to be latched so that we can have all of the demuxed signals active at a time. Which is why I was looking at latches in the first place.

  • 0 in reply to Dakota Roscoe
    TI__Mastermind 45575 points
    Dakota,

    The switch devices are passive FET switches and are bi-directional so you can use them in either direction.

    Thank you,
    Adam