SAW Components
SAW RF filter
Data sheet
ESD protection of SAW filters
B3761
315.00 MHz
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.
Ls3
MLC1
Ls3
to output
matching
to output
matching
Lp2
Dp1
Lp2
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.
Ls2
to output
matching
Cs1
to output
matching
Lp1
Lp2
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”.
Please read
cautions and warnings and
important notes
at the end of this document.
6
December 18, 2008
EPCOS [ EPCOS ]
