USBDFXXW5(2000) データシートの表示（PDF） - STMicroelectronics

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USBDFXXW5
(Rev.:2000)

EMI FILTER AND LINE TERMINATION FOR USB DOWNSTREAM PORTS

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USBDFxxW5

Fig. A8: Analog Crosstalk measurements

50 Ω TG OUT

Vg

TEST BOARD

RF IN

50 Ω

Fig. A9: Typical Analog Crosstalk results

Analog crosstalk (dB)

0

-20

-40

-60

-80

-100

1

10

100

frequency (MHz)

1,000

Figure A8 gives the measurement circuit for the analog crosstalk application. In figure A9, the curve shows

the effect of the D+ cell on the D- cell. In usual frequency range of analog signals (up to 100MHz) the effect

on disturbed line is less than -46dB.

Fig. A10: Digital crosstalk measurements configu-

ration

Fig. A11: Digital crosstalk results

Square

Pulse

Generator

5KHz

+5V

74HC04

Line 1

+5V

VG1

Line 2

+5V

74HC04

USBDF

xxW5

b21 VG1

Figure A10 shows the measurement circuit used to quantify the crosstalk effect in a classical digital appli-

cation.

Figure A11 shows that in such a condition signal from 0 to 5V and rise time of few ns, the impact on the

other line is less than 100mV peak to peak (Below the logic high voltage threshold).The measurements

performed with falling edges give the same results.

7/9

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