USB6B1 Ver la hoja de datos (PDF) - STMicroelectronics

Número de pieza

componentes Descripción

Fabricante

USB6B1

DATA LINES PROTECTION

STMicroelectronics 

HOW TO ENSURE A GOOD ESD PROTECTION

While the USB6Bx provides a high immunity to

ESD surge, an efficient protection depends on the

layout of the board. In the same way, with the rail to

rail topology, the track from the VCC pin to the

power supply and from the GND pin to GND volt-

age must be as short as possible to avoid

overvoltages due to parasitic phenomena (see Fig

A1).

It’s often harder to connect the power supply near

to the USB6Bx unlike the ground thanks to the

ground plane that allows a short connection.

To ensure the same efficiency for positive surges

when the connections can’t be short enough, we

recommend to put close to the USB6Bx between

VCC and ground, a capacitance of 100nF to pre-

vent from these kinds of overvoltage disturbances

(see Fig. A2 ).

USB6Bx

Fig. A2: ESD behavior: optimized layout and add

of a capacitance of 100nF.

ESD

SURGE

Lw

C=100nF

REF2=+Vcc

I/O

VI/O

Vcl+ = Vcc+Vf surge >0

Vcl- = -Vf surge <0

REF1=GND

Vcl+

POSITIVE

SURGE

t

NEGATIVE

SURGE

The add of this capacitance will allow a better pro-

tection by providing during surge a constant volt-

age.

Fig. A3 shows the improvement of the ESD pro-

tection according to the recommendations de-

scribed above.

t

Vcl-

IMPORTANT:

A main precaution to take is to put the protection

device closer to the disturbance source (generally

the connection).

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