Because of the Thanksgiving holiday in the U.S., TI E2E™ design support forum responses may be delayed from November 25 through December 2. Thank you for your patience.

  • State TI Thinks Resolved
  • Locked Locked
  • Replies 12 replies
  • Answers 2 answers
  • Subscribers 19 subscribers
  • Views 3054 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN74ALVCH16373: Timing Requirements

Scott Asher
Intellectual 500 points
Part Number: SN74ALVCH16373
Other Parts Discussed in Thread: SN74LVTH16373-EP, SN74ALVC32

Hello. I have some questions regarding timing parameters for the SN74ALVCH16373. The timing requirements tW, tSU, tH refer to figure 1 in the datasheet.  The input column in the figure table list Tr/Tf as </= 2.5ns. My questions are:

1) Is Tr/Tf measured at 10% to 90%, or is it 20% to 80%?

2) My Hyperlynx slow-weak corner simulations are reporting Tr = 5.35ns and  Tf = 5.56ns on the D inputs. For LE inputs it is Tr = 1.7ns and Tf = 1.34ns.  These measurements are using the 10/90 setting rather than the 20/80 setting in Hyperlynx. Figure 1 in the datasheet indicates tSU, tH, and tW are measured to Vm = 1.5V for the conditions Vcc = 3.3V and Tr/Tf </= 2.5ns. My question is, if Tr/Tf is > 2.5ns, does that mean we cannot use the Vm point for these measurement? Should we instead use the Vil and Vih points to measure the timing margins?

3) If we must use the Vil/ViH points for the D inputs since their Tr/Tf is > 2.5ns, does that mean we also need to use the Vil/Vih points on the LE input, or can we instead still measure to Vm on the LE input since its Tr/Tf is < 2.5ns?

Thanks,

Scott

  • 0
    TI__Guru* 96842 points

    Hi Scott,

    1. For TI datasheets, tr is defined as 10% to 90% unless otherwise specified. (section 4.9.12 of Understanding and Interpreting Standard-Logic Data Sheets (Rev. C))

    2.That Vm point is still valid for the measurements -- the data table on the parameter measurement information page of the datasheet is there to let you know how we tested the part -- just because we used a signal that was <= 2.5ns doesn't mean you have to use on that matches that spec.

    This additionally makes sense since you are trying to measure from the time the device switches states until the output changes -- and CMOS devices keep the same threshold regardless of the input's rate of change.

    3. I would not use Vil/Vih - they are not telling you a threshold, but are suggesting an input value to guarantee a 'low' or 'high' input (respectively).  Vm is closer to the actual switching threshold and thus should be used for timing calculations.

  • 0 in reply to Emrys Maier
    Intellectual 500 points
    Hi Emrys,

    Thanks for your response! We'll use Vm for our timing measurements as you suggest. Would your answers above be the same for the M version of the sn74lvth16373-ep? We are thinking of using that part instead since it is 125C and need to know if should use Vm for timing even though we are seeing > 2.5ns Tr/Tf input for this part as well.

    Thanks again!

    Scott
  • 0 in reply to Scott Asher
    TI__Guru* 96842 points
    I would recommend the same testing methodology, but the EP part falls under a different group inside TI because of the much stricter requirements for those parts. I will notify them to take a look at this thread.
  • 0 in reply to Emrys Maier
    TI__Guru 62930 points

    Scott,

    I agree with Emrys.

    The timing and parametric information for the EP version of the device is the same as in the commercial version.

    The methodology you are using will apply to both.

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    Intellectual 500 points
    Thanks Emrys and Wade for your responses!

    I have some follow-up questions regarding the SN74ALVCH16373. This chip is only rated for temps up to 85 degrees C but we need to run at 105 degree C. I know the M version of the EP part could do this but it only comes in BGA package which we currently cannot use. Please see another post titled "SN74ALVC32 propagation delay over temperature". This post has an attached characterization data file titled "ALVC32_A.pdf". This file has TPLH/TPHL measurements at both 85C and 125C temps. Would we be able to use this data file to extrapolate what the Tsetup, Thold, Tw, Tpd, etc. numbers would be at 105 degrees C for the SN74ALVCH16373? Do you have a similar characterization data file for the SN74ALVCH16373 that you could provide?

    Thanks again!

    Scott
  • 0 in reply to Scott Asher
    TI__Guru 62930 points

    Scott,

    I am unsure if there is any characterization data showing trend. Possibly Emrys is aware of some and can reply.

    However, you reference an SN74ALVCH16373-EP for M temp.   Best I can tell, this part does not exist.   Can you point to the orderable part number for verification?

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    Intellectual 500 points

    I was referring to the M version of the sn74lvth16373-ep. But we cannot use this part since it is BGA package.

    So my questions in my previous post regarding temp derating to 105C are more for the SN74ALVCH16373DGGR, which I believe is in Emrys's group.

    Emrys, can you answer the temp derating questions in my previous post with regards to the SN74ALVCH16373DGGR?

    Thanks,

    Scott

  • 0 in reply to Scott Asher
    TI__Guru* 96842 points
    Hi Scott,
    In order to guarantee the part at a temperature higher than its current rating, we would have to start a project to re-characterize the device across the new temperature range. Right now I can only guarantee the device to the current datasheet values.

    Can you tell me about the timeline for your project? How soon would you need a 125C rated version of this device? Also, would it need to be 'EP' or would a commercial version work?
  • 0 in reply to Emrys Maier
    Intellectual 500 points

    Hi Emrys,

    Thanks for update. We need the 125C rated parts by mid 2018. Here is a list of all the ALVC parts that are currently rated to 85C that we need rated to 125C. Don't need to be EP.

    SN74ALVC32PW

    SN74ALVC10PWR

    74ALVC08PW_112

    74ALVC74PW,118

    74ALVC00PW,112

    SN74ALVC32DG4

    SN74ALVCH16373DGGR

    SN74ALVC125PWG4

    Thanks,

    Scott

  • 0 in reply to Scott Asher
    TI__Guru* 96842 points
    Hey Scott,
    I have asked my marketing team to contact your local TI sales team to work on the details for this request. I think this is a reasonable request, it will just be a question of resources on our end.
  • 0 in reply to Emrys Maier
    Intellectual 500 points

    Hi Emrys,

    Thanks for the response. This project I'm working is out of Honeywell site in Tucson, Arizona if that makes a difference to you as far as what TI sales team to work with.

    Thanks,

    Scott

  • 0 in reply to Scott Asher
    TI__Guru* 96842 points
    Thanks Scott,
    I talked to my marketing folks who said they have already gotten in contact with the right sales team out there. Let me know if I can be of any further assistance!