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150 mhz 32 bit counter

Other Parts Discussed in Thread: SN74AUP2G80, SN74LV4040A, SN74HC688, LMK00804B, SN74AUC74, SN74LVC2T45, CD74AC161, SN74LV8154, SN74HC4040

I need to make a 32 bit frequency counter for 150 MHz. Probably first part of counter would need to be ECL. parallel out. or maybe the 32 bit counter for your micro.

  • Hello Alvin,

    I think most of our clock generators will work for your need. I am sure there will be additional needs in your application. Please take a look at our Quick search tool to search for specifically what is needed here.

    The Quick search tool can help search our clock generators by function, number of outputs, output types, output frequency, input type as well as other desired features if desired.

    Feel free to ask about these devices meeting needs.

  • I do not need to generate a clock but I need a 32 bit counter with 32 parallel outputs that will receive a RF signal of up to 150 MHz as input (properly amplified of course) for 1 second of time and then tell me the exact frequency down to the single hertz. 

  • Hello Alvin,

    Sorry for the confusion. We have another Responsible Organization that will discuss with you the options here at TI.

    I'll transfer this over to them now!

  • Alvin,

    While we await a response from the other team, I want to point out that this seems like something you could handle with a CPLD and an RF-to-CMOS buffer. To be more precise, it sounds like you need some basic building blocks:

    • A precise reference such as an OCXO or some kind of GPS lock, which has an accurate representation of one second
    • A counter that can count up to 150MHz, and another counter for your precise reference
    • A mechanism to synchronously enable or disable the measurement counter from the reference counter
    • Some device which can accept an RF signal in, and produce a counter-compatible signal out (LVCMOS or equivalent)

    I think the easiest option for a high precision reference is an LVCMOS OCXO (there are many at 10MHz which works well with most discrete or CPLD digital logic). If you have some other reference in mind, we could offer more guidance about how best to use it (if needed).

    The counter is the simplest of these building blocks; a good starting point is the cascaded SN74LV4040A, operational up to around 75MHz with light loading at 3.3V supply (higher at 5V, but doesn't function with 3.3V I/O then), which should be sufficient for any OCXO or frequency reference, and gets most of the way to a good measurement counter. I checked our counter portfolio but I don't think we have any discrete counters rated for 150MHz at 3.3V; consequently, the first stage (or two, to be safe) into the measurement counter should probably be driven by D-flip-flop(s) with Qbar tied to D (e.g. SN74AUP2G80). Again, a single CPLD could likely replace all of these counters, though you may still want to add a stage or two of external D-flip-flops to reduce the input frequency range to the CPLD if there are any worries about meeting setup and hold requirements at 150MHz. Note that preset and clear are not necessary for operation: you can always just perform the difference between the start and the stop counts.

    You will also need some logic to reset the counter and decode the reference count to a start-stop enable pulse lasting one second. A discrete implementation might involve a handful of digital comparators (e.g. SN74HC688) looking for the exact value of one second of reference pulses, triggering an S-R latch tied to the counter clear and the measurement counter window; some measurement toggle could reset the latch to begin the measurement count, the reference counter would exit the clear condition and begin counting, and would automatically halt at the preprogrammed value. Again, this could be done with a CPLD as well, for much lower cost and component count.  

    To convert your measurement RF signal to an LVCMOS signal, an input buffer like LMK00804B could be used. Since LMK00804B has a synchronous enable, starting and stopping the frequency counter cleanly is very easy: attach the enable to your reference counter S-R latch or your CPLD equivalent. If your measurement signal is always going to be around 150MHz there likely will not be problems with slew rate, but if the measurement signal could be lower frequency (e.g. 15MHz) this could cause issues with slew rate; an alternate low-frequency path through a high-speed comparator may be advisable.

    Regards,

  • All I asked for is the counter. I can do all the glue logic as well as do most of it with a microchip pic computer. I do not need precise timing for the 1 second interval. a 32768 crystal is good enough for my receiver output. What d flipflop is rated for 5 ns? What was the 75 MHz 32 bit counter?

  • I need 5 volt devices

  • Hey Alvin, We don't have anything that will meet all of your requirements in a single device.

    For your first stage, I don't think you're going to find a 5V logic device that supports 150 MHz frequency division (counting) directly. You could try the "F" or "AC" logic families, as they are the fastest options, however 150 MHz is not guaranteed in the datasheet so even if it worked, you'd be taking a risk.

    If you can step that 5V signal down to 2.5V, then the AUC family of logic is fast enough to be your input stage. SN74AUC74 supports up to 350 MHz clock input frequency at 2.5V supply, so it would have any easy time with this. With this device, you have two D-type flip-flops, so you could do two divisions and get down to 37.5 MHz, which puts you in the range of at least some of our counter portfolio.

    For these first two stages you'll need something to step up the output to 5V, so I'd recommend using the SN74LVC2T45 for that (dual supply level translator).

    The CD74AC161 supports up to ~100 MHz at 5V, so that could be used next, but it's only a 4-bit counter, so you'd have to glue together quite a few of those to get all 30 remaining bits.

    The SN74LV8154 is a 16-bit counter that supports 40 MHz assuming a light load (15 pF), however it only has 8 outputs and you have to switch between two banks to get all 16-bits to the output. I'm assuming this isn't something you want to do, but this is an 'honorable mention.'

    The SN74HC4040 has the highest number of bits that are all available as outputs, with 12 bits total. The maximum frequency of this device is only 25 MHz across temperature, so it would have to be a third stage.

    --edited for formatting, the system removed all my line breaks for some reason--

  • Thank you for taking the time to answer my question. I was considering using the device that has two 16 bit counters with 8 bits out. I will be using a uP to control the system so an 8 bit i/o I2C device would be what I would use.  I am stuck back in the dark ages with HC (74HC) devices so I will enjoy learning about the devices you suggested. I plan to close this as I have much to do with what you have given me. Thanks again.