Location for HSP061-8M16

AN3357

2/10

Doc ID 018580 Rev 1

1

Location for HSP061-8M16

Many PCB parasitic elements may degrade the overall ESD performance of a system. The

recommendations below are aimed at optimizing ESD protection device placement and the

PCB layout to reach the best ESD performance possible.

The layout shown in Figure 1 may induce parasitic inductances responsible for artificial

overvoltages directly applied on the IC to be protected.

A very simple calculation shows that for a 15 kV ESD contact surge according to

IEC61000-4-2, the overvoltage due to parasitic inductances may be really significant, as

shown in Figure 2. This test is done with a contact discharge as the air discharge waveform

is not defined in the IEC 61000-4-2 specification. Assuming that each inductance value is 5

nH (corresponds to metal track 5 mm long):

then the overvoltage seen by the IC is:

This parasitic inductance must be reduced as much as possible by shortening the ground

path return to the GND via.

To avoid ESD propagation on the PCB, the ESD protection must be placed as close as

possible to the ESD source with the layout given in the datasheet.

The layout given in the datasheet reduces parasitic inductance. It is important to connect the

connector on one side of the HSP and the transceiver on the other side. The GND via on

both sides must be used.

As ESD stress can be propagated on both sides of the cable, a protection device on each

end of the cable is required.

Figure 1.

Non-optimized location for

HSP061-8M16

Figure 2.

Significant overvoltages due

to non-optimal location of

HSP061-8M16

Via to GND

IC to

protect

Via to

GND

2

4

5

3

6

7

8

1

16

15

13

12

14

11

10

9

16

G

N

D

IC to

protect

Via to

GND

V

dt

di

L

ESD surge is 15 kV with 1 ns

rise time, this leads to 71 A/ ns

GND layer

di

dt

= 71 A/ns

L·

di

dt

V

= V +

IC

V

= V + 355 V

IC