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USBUF01W6

EMI FILTER AND LINE TERMINATION FOR USB UPSTREAM PORTS

STMicroelectronics 

Fig. A9: Analog crosstalk measurements

50Ω

Vg

TEST BOARD

UUx

50Ω

USBUFxxW6

Fig. A10: Typical analog crosstalk results

Analog crosstalk (dB)

0

-20

-40

-60

-80

-100

1

10

100

Frequency (MHz)

1,000

Figure A9 gives the measurement circuit for the analog crosstalk application. In figure A10, 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 -37dB.

Fig. A11: Digital crosstalk measurements configuration

Square

Pulse

Generator

+5V

+5V

74HC04

D+

D1

VG1

Gnd

D-

D2

3.3 V

Rt Rp

Ct

D4

+5V

74HC04

3.3 V

Rt

Ct

D3

β21 VG1

Figure A11 shows the measurement circuit used to quantify the crosstalk effect in a classical digital appli-

cation.

Fig. A12: Digital crosstalk results

Figure A12 shows, with a signal from 0 to 5V and

rise time of few ns, the impact on the disturbed line

is less than 250mV peak to peak. No data distur-

bance was noted on the other line.The measure-

ments performed with falling edges gives an

VG1

impact within the same range.

β21VG1

7/9

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