USBDFXXW5(2000) Просмотр технического описания (PDF) - STMicroelectronics

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производитель

USBDFXXW5
(Rev.:2000)

EMI FILTER AND LINE TERMINATION FOR USB DOWNSTREAM PORTS

STMicroelectronics 

USBDFxxW5

Fig. A6: Remaining voltage at both stages S1 (Vinput) and S2 (Voutput) during ESD surge.

a. Positive surge

b.Negative surge

Please note that the USBDFxxW5 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 Fig. A6b.

LATCH-UP PHENOMENA

The early ageing and destruction of IC’s is often due to latch-up phenomena which is mainly induced by

dV/dt. Thanks to its structure, the USBDFxxW5 provides a high immunity to latch-up phenomena by

smoothing very fast edges.

CROSSTALK BEHAVIOR

Fig. A7: Crosstalk phenomena

RG1

Line 1

VG1

RG2

Line 2

RL1

α1 VG1 + β12 VG2

VG2

RL2

α2 VG2 + β21 VG1

DRIVERS

RECEIVERS

The crosstalk phenomena is due to the coupling between 2 lines. The coupling factor ( β12 or β21 ) increases

when the gap across lines decreases, this is the reason why we provide crosstalk measurements for

monolithic device to guarantee negligeable crosstalk between the lines. In the example above the ex-

pected 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 phe-

nomenon 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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