APPLICATION INFORMATION

SSC MODULATION

PARAMETER MEASUREMENT INFORMATION

VDD

1kW

1kW

10pF

LVCMOS

CDCS501

LVCMOS

LVCMOS

CDCS501

TypicalDriver

Impedance

~32 W

SeriesTermination

~18 W

Z =50

L

W

CDCS501

www.ti.com..................................................................................................................................................................................................... SCAS874 – APRIL 2009

The exact implementation of the SSC modulation plays a vital role for the EMI reduction. The CDCS501 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 the below formula.

fmod = fIN / 2480

Figure 2. Test Load

Figure 3. Test Load for 50-

Ω Board Enviroment

Copyright © 2009, Texas Instruments Incorporated

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Product Folder Link(s): CDCS501