DM505 datasheet(217/295 Pages) TI2

217 / 295 page

SPRS91v_PCB_FREQ_03

1.0e+01

1.0e+00

1.0e–01

1.0e–02

1.0e–03

1.0e–04

1.00e–002

1.00e+000

1.00e+002

Frequency (MHz)

1.00e+004

1.00e+006

1.00e+008

S-Parameter Magnitude

Job: GCM155R71E153KA55_15NF;

X =1/ C

X = L

L ω

Resonant frequency

(55 MHz) (minimum)

where :

w =

ESR +ωESL

ωC

2π

ωESL

ωC

SPRS91v_PCB_FREQ_02

ESL

ESR

SPRS91v_PCB_FREQ_01

217

DM505

www.ti.com

SPRS976E – NOVEMBER 2016 – REVISED MAY 2018

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Applications, Implementation, and Layout

•

Decoupling capacitors must be carefully placed in order to minimize loop inductance impact on supply

voltage transients. A real capacitor has characteristics not only of capacitance but also inductance and

resistance.

Figure 7-6 shows the parasitic model of a real capacitor. A real capacitor must be treated as an RLC

circuit with effective series resistance (ESR) and effective series inductance (ESL).

Figure 7-6. Characteristics of a Real Capacitor With ESL and ESR

The magnitude of the impedance of this series model is given as:

Figure 7-7. Series Model Impedance Equation

Figure 7-8 shows the resonant frequency response of a typical capacitor with a self-resonant frequency of

55 MHz. The impedance of the capacitor is a combination of its series resistance and reactive capacitance

and inductance as shown in the equation above.

Figure 7-8. Typical Impedance Profile of a Capacitor

DM505 Datasheet(PDF) 217 Page - Texas Instruments

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