USBUF(2006) データシートの表示（PDF） - STMicroelectronics

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USBUF
(Rev.:2006)

EMI filter and line termination for USB upstream ports

STMicroelectronics 

Technical information

USBUFxxW6

Figure 8. Remaining voltage at both stages S1 (Vinput) and S2 (Voutput) during

ESD surge

Vin

Vout

Vin

Vout

Positive surge

Negative surge

Please note that the USBUFxxW6 is not only acting for positive ESD surges but also for

negative ones. For these kinds of disturbances it clamps close to ground voltage as

shown in Figure 8. (negative surge.

2.4

Latch-up phenomena

The early ageing and destruction of IC’s is often due to latch-up phenomenon which is

mainly induced by dV/dt. Thanks to its structure, the USBUFxxW6 provides a high immunity

to latch-up phenomenon by smoothing very fast edges.

2.5

Crosstalk behavior

Figure 9.

Crosstalk phenomenon.

RG1

Line 1

VG1

RG2

Line 2

VG2

RL1

α1 VG1 + β1 V2 G2

RL2

α2 VG2 + β2 V1 G1

DRIVERS

RECEIVERS

The crosstalk phenomenon is due to the coupling between 2 lines. The coupling factor (β12

or β21) increases when the gap across lines decreases, particularly in silicon dice. In the

example above the expected signal on load RL2 is α2VG2, in fact the real voltage at this point

has got an extra value β21VG1. This part of the VG1 signal represents the effect of the

crosstalk phenomenon of the line 1 on the line 2. This phenomenon has to be taken into

account when the drivers impose fast digital data or high frequency analog signals in the

disturbing line. The perturbed line will be more affected if it works with low voltage signal or

high load impedance (few kΩ).

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