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Jitter Budget Calculator

This calculator provides a conservative estimate of output total jitter (TJ) when connecting several elements in series, given each element's jitter contribution in terms of its random (RJ) and deterministic jitter (DJ) components. Alternatively, one may begin with a target output total jitter, then budget jitter to each element in the link to meet this target. In either case, each element's jitter may be tweaked to understand its effect on system performance while optimizing a jitter budget.

Note that this simple calculator makes many assumptions that tend to over-estimate the output node's total jitter value. Use it with the intent of revealing potential problems in a system, rather than guaranteeing the system will work trouble-free.

Definition of Element and Node.

Step 1:  Enter N N is the "crest factor" indicating how many standard deviations out you wish to include when converting RJ (ps RMS) to RJ (ps PP). See below for more information.

Step 2:

In the table below, enter data in columns for (1) Description (optional), (2) DJ (ps PP), and (3) RJ (ps RMS).

Step 3:

Enable data by selecting its corresponding checkbox (calculation includes data up to the first un-selected Enable Data box; spacebar toggles checkbox).

Step 4:

Click on "Calculate" button below.


Enable
Data		 Element Elemental Jitter Budget Node Nodal Jitter Budget % of Jitter
Budget
         DJ RJ RJ   DJ RJ TJ  
  # Description (ps PP) (ps RMS) (ps PP)   (ps PP) (ps PP) (ps PP) (%)
1 A
2 B
3 C
4 D
5 E
6 F
7 G
8 H
9 I
10 J
11 K
12 L

      

Supplemental Information

The following figure shows the total jitter histogram (or, PDF), decomposed into deterministic and random components of jitter. The DJ component is modeled using a dual-delta function, which is then convolved with an RJ distribution (e.g. Gaussian PDF) to obtain the TJ distribution. The parameters identified below are used in the calculator above.

Jitter PDF Showing DJ, RJ and TJ



Note that although the type of jitter is not specified here (e.g. time-interval error, period jitter, cycle-to-cycle jitter, etc.), the calculator assumes all of its entries refer to the same type of jitter each time the "Calculate" button is clicked. The type of jitter used should be determined by the end application.

N may be estimated using the Gaussian statistics tables to the right. Select an appropriate value of N with the end application in mind. For example, setup-and-hold time applications may prefer period jitter using the % population table (e.g. N=6 for +/-3 sigma is a popular choice). High-speed serial standard applications may prefer time-interval error jitter using the BER table (e.g. N=14.069 for BER=1E-12 is specified in several popular standards).

Additional information regarding N, including its calculation, may be found on the RMS to Peak-to-Peak Jitter Calculator web page.

   Jitter BER Gaussian Statistics Table
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