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SN74CBT16245DL

Michael Madaris
Prodigy 30 points
Other Parts Discussed in Thread: CD4016B

I'm trying to use an IC bus chip, to provide a switching solution.  We had "Black Box" make us a selector switch, that isolated incoming Cat 6 connections to microphones.  The Black Box switches mechanically fail very quickly.  We use a set of (4) microphones, at 4 different distances, to provide our targeting or dispersion of ammunition.  The microphones find the location of apparent bullet coordinates, much the same as a computer mouse coordinates are arrived at.  The signals from the microphones are amplified to +15VDC.  The different target locations need to be isolated for different range tests.  I was hoping I could use the SN74CBT16245DL to be the "Switches" in a circuit, that might do the same thing as the mechanical "Black Box" switch set up.  We would use a logic 1 or other signal to operate the transfer of the incoming +15VDC signals to connect to the chips output for the different incoming target signals.  I'm having trouble finding a prototype board to solder the IC to.  It appears to have a pitch of .035" (.889mm).  I would need a breadboard that could service at least (3) of these IC's, and possibly other logic and passive components.  Any idea's?

  • 0
    TI__Guru 53082 points

    Hi Michael,

    We don't directly make an adapter - but there should be 48 pin SSOP to DIP adapters available on the market - however I do have some concerns with the IC chosen for this application. 

    To clarify - are you trying to pass +15VDC signals through the SN74CBT16245DL? If I am understanding this correctly - this part will not be able to work in this application. It has a max rec. operating voltage supply of 5.5V and this device will not be able to pass that signal without being able to suffer damage.

    However we do have a decent amount of options of parts that can help in this application . I would be more than willing to help you narrow down potential parts for the application if you can provide a bit more information:

    1. Can you Confirm the Microphone signal being passed through the IC is DC - if not what is the expected bandwidth?

    2. Are you able to supply a 15V or greater supply voltage to allow the Multiplexer to pass the required voltage?

    3. What Are the Loading Conditions of the Microphone - i.e. when the microphone sends a signal back to the processing source - what is the approximate impedance (if it is high impedance you can just leave it at that)?

    4. Is there anything that drew you to the SN74CBT16245DL in the first place - this is so I can keep this in mind when looking through the possible options.

    5. Does the Package need to be leaded? Are there space or layout constraints that you are working with?

    Also just as a note the devices we do have available for this application are at most 4 channels - however the these parts have options that can shrink the footprint to keep it in line with the ~164mm^2 footprint that the SN74CBT16245DL has.

    Please let me know so I can see what the best solution we have for you is!

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    Prodigy 30 points

    Thanks for getting back to me on my project!  We have a 200 yard underground test alley, with a set of (4) piezo element microphones at 50, 100, and 200 yards, as well as at a 100 meter location.  The microphones are on and running 24x7.  The switch box we were using, selected only the locations we were testing at.  The microphones generate a small garbled signal when the sonic cone from a projectile passes through the target plane.  The +15VDC target amplifiers condition this signal to get it up range, to the data acquisition system.  We would be passing +15VDC to the device at it's switch over connections.  The microphone signals are DC.  I believe the data acquisition system is picking on the leading rising edge of the garbled signal.  We could power the device externally if needed.  When I reverse engineered the "Black Box" switch unit, I took notes on the configuration of the (3) mechanical switches within it.  Depressing a combination of (3) switches, would enable it to isolate whichever target location Cat 6 cable was plugged into it.  I stumbled onto the SN74CBT12645DL, and noticed that it was configured in much the same way as the mechanical switches.  I figured if I could provide any combination of logic 1 or other signal to the bus high or low inputs, it would isolate which ever Cat 6 connection I required.  We do not have BGA capability here, so unless we sent the device you might find for us out to a board house, I would be soldering it onto prototype pcb's.  At this point, it's all in my head, so there are no apparent space or layout constraints.  Just to add a bit more info., when I look at the microphone signals on an o-scope, they appear much the same as "switch bounce".

  • 0 in reply to Michael Madaris
    TI__Guru 53082 points

    Hi Michael,

    Thanks for the extra information!

    I think we have a couple options that may be useful in this application.

    2 Caveats that apply to all of them are the following:

    1. ON Resistance is going to be higher on all of our available options - this means the voltage read at the data acquisition system is going to be

    V_dataAq =   R_dataAq / ( R_dataAq + R_On) ---> If the impedance of the data acquisition is high - which I'd assume it probably is the insertion loss of the switch is going to be lower, but it is something to be aware of .

    2. The rated switch current is much lower on these devices (10mA - 30mA)  - where the SN74CBT1264DL can have 128mA. This depends on the impedance of the data acquisition system - if this is high impedance this shouldn't be a concern - but it is something to be aware of.

    With that being said:

    The first option is the CD4016B - this is available in a few different leaded packages that have DIP adapters available at market to test the system. It can pass a 15V DC signal if the supply is >= 15V. It is only 4 channels - so to get the same amount of channels 4 of them would need to be used. It has a lower bandwidth of 40MHz - but with the signal being passed I don't think this should be an issue. This part only has a 10mA current limit through each channel.

    The second option is a part from the TMUX611X (6111/6112/6113) line of parts. They can pas a 15V DC signal with a VDD >= 15V.  They are precision parts that have very low leakage and are great parts to use in mid-voltage data acquisition systems. The only difference between the three parts is if they are active high/ active low/ or a combination. These parts are offered in TSSOP packages which are leaded and have break-out dip adapters available. This part is more expensive than the CD4016B due to its improved specs - low charge injection, low leakage current, and lower on resistance to name a few. It also can handle 30mA of current through the switch. This part will alter the signal less than the CD4016B - but I am not sure if that level of precision would be required in this application. 

    Please let me know if you have any other questions or if there is issues with the proposed solution and I will see what I can do!

    Best,

    Parker Dodson