SR12

4

05255.R0 9/06

www.protekdevices.com

APPLICATION NOTE

The SR12 is a low capacitance, unidirectional TVS array that is designed to protect I/O or high speed data lines from the damaging effects of ESD or

EFT. This product series has a surge capability of 500 Watts P

COMMON-MODE CONFIGURATION (Figure 1)

Ideal for use in USB applications, two SR12 devices provides up to two(2) lines of protection(per device) in a common-mode configuration as

depicted in Figure 1.

Circuit connectivity is as follows:

✔

Pins 2 and 3 are connected to the datalines.

✔

Pin 1 is connected to ground.

✔

Pin 4 is connected to the databus.

CIRCUIT BOARD LAYOUT RECOMMENDATIONS

Circuit board layout is critical for Electromagnetic

Compatibility (EMC) protection. The following

guidelines are recommended:

✔

The protection device should be placed near the

input terminals or connectors, the device will

divert the transient current immediately before it

can be coupled into the nearby traces.

✔

The path length between the TVS device and

the protected line should be minimized.

✔

All conductive loops including power and

ground loops should be minimized.

✔

The transient current return path to ground

should be kept as short as possible to reduce

parasitic inductance.

✔

Ground planes should be used whenever

possible. For multilayer PCBs, use ground vias.

Figure 1. Typical Common-Mode USB Protection

1

2

3

4

1

3

4

2

VBus

VBus

VBus

VBus

D+

D-

D+

D-

USB

PORT

USB

PORT