6

March 22, 2007

B3737

447.725 MHz

Please read

cautions and warnings and

important notes at the end of this document.

SAW Components

SAW filter

Data sheet

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 two figures show recommended “ESD matching” topologies.

Depending on the input impedance of the SAW filter and the source impedance, the needed

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.

Fig. 3 shunt L – series L matching

Fig. 4 series C – shunt L matching

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

“data sheets” and then “Applications” under category “Further information”.

Lp2

Ls3

to output

matching

Lp2

Ls3

Dp1

matching

to output

Lp1

Ls2

matching

to output

Lp2

Cs1

matching

to output