USB6B1 datasheet(3/9 Pages) STMICROELECTRONICS

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USB6Bx

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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 ).

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.

HOW TO ENSURE A GOOD ESD PROTECTION

Fig. A2: ESD behavior: optimized layout and add

of a capacitance of 100nF.

REF1=GND

VI/O

ESD

SURGE

I/O

REF2=+Vcc

C=100nF

Vcl+ = Vcc+Vf

-Vf

surge >0

surge <0

Vcl- =

Vcl+

POSITIVE

SURGE

Vcl-

NEGATIVE

SURGE

IMPORTANT:

A main precaution to take is to put the protection

device closer to the disturbance source (generally

the connection).

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