ST AN2455 Application note

AN2455

Application note

STWPLLSim phase noise and settlin g time sim ulator for STW8110x

Application and scope

The STWPLLSim tool helps the end user to design the optimal loop filter for the STW81101x
synthesizers. It provides a very accurate estimation of the overall phase noise and settling
time performances, allowing the user to interactively compare measurements with simulated
performance.

July 2007 Rev 2 1/14

www.st.com

Installation AN2455

1 Installation

The STWPLLSim software is written in Java and designed to run on Windows 2000/XP. To
perform time domain simulations, STWPLLSim requires the MATLAB Component Runtime
(MCR) Libraries (Copyright 1984-2005, The MathWorks, Inc. See

http://www.mathworks.com/access/helpdesk/help/toolbox/compiler/index.html?/access/help
desk/help/toolbox/compiler/f12-999353.html

Run

SETUP.bat

to install STWPLLSim.

).

2 Main form

Figure 1. STWPLLSim: main form and project flow

1

3

4

6

2.1 Creating and managing projects

New and Open buttons allow the user to create a new project or to open an existing one.
The project can be save d by pressing the Save / Save As buttons.

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AN2455 Main form

2.2 Project flow

These are the steps to follow in using STWPLLSim, as shown in

1. Main settings (see the screenshot in
a) Device choice (STW81101, STW81102, STW81103)
b) Output frequency [MHz]
c) Frequency step [kHz]
d) Output stage (direct output, divider by 2, divider by 4)
e) VCO and phase detector frequencies are calculated from the inserted data.
f) A table helps to choose the correct output stage depending on the desired output

frequency and the selected device.

Figure 2

):

Figure 1

:

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Main form AN2455

Figure 2. Main settings

1a

1b

1c

1d

1e

1f

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AN2455 Main form

2. Prescaler: select the prescaler (either 16/17 or 19/20).

3. Reference clock (see the screenshot in

Figure 3

):
a) Reference frequency
b) Fitting parameters for phase noise performance

Figure 3. Reference clock settings

3a

3b

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