APPLICATION INFORMATION

SSC MODULATION

PARAMETER MEASUREMENT INFORMATION

VDD

1kW

CDCS503

LVCMOS

1kW

10pF

LVCMOS

LVCMOS

CDCS503

TypicalDriver

Impedance

~32 W

Series Termination

~18 W

Z =50

L

W

CDCS503

www.ti.com .................................................................................................................................................................................................. SCAS872 – MARCH 2009

The exact implementation of the SSC modulation plays a vital role for the EMI reduction. The CDCS503 uses a

triangular modulation scheme implemented in a way that the modulation frequency depends on the VCO

frequency of the internal PLL and the spread amount is independent from the VCO frequency.

The modulation frequency can be calculated by using one of the below formulas chosen by frequency

multiplication mode.

FS = 0: fmod = fIN / 708

FS = 1: fmod = fIN / 620

Figure 2. Test Load

Figure 3. Load for 50-

Ω Board Environment

Copyright © 2009, Texas Instruments Incorporated

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Product Folder Link(s): CDCS503