5

December 08, 2011

B4310

1588.655 MHz

SAW Components

SAW RF filter

Data sheet

Please read

cautions and warnings and

ESD protection of SAW filters

SAW filters are Electro Static Discharge sensitive devices. To reduce the probability of damages

caused by ESD, special matching topologies have to be applied.

In general, “ESD matching” has to be ensured at that filter port, where electrostatic discharge is

expected.

Electrostatic discharges predominantly appear at the antenna input of RF receivers. Therefore

only the input matching of the SAW filter has to be designed to short circuit or to block the ESD

pulse.

Below three figures show recommended “ESD matching” topologies.

ensure a proper matching for any impedance value of antenna and SAW filter input. The required

component values have to be determined from case to case.

Fig. 1 MLC varistor plus ESD matching

Fig. 2 Suppressor diode plus ESD matching

In cases where minor ESD occur, following simplified “ESD matching” topologies can be used

alternatively.

In all three figures the shunt inductor Lp2 could be replaced by a shorted microstrip with proper

length and width. If this configuration is possible depends on the operating frequency and

available pcb space.

Effectiveness of the applied ESD protection has to be checked according to relevant industry

standards or customer specific requirements

For further information, please refer to EPCOS Application report:

“ESD protection for SAW filters”.

This report can be found under www.epcos.com/rke.Click on “Applications Notes”.

Cs1

Lp2

Cs3

to output

matching

Lp2

Cs3

Cs1

to output

matching

Lp2

Cs3

Cs1

to output

matching