Conclusion

AN2456

14/15

The protection solution was tested for all configurations, but only two are illustrated for

brevity. All other test results are available upon request. The TCP 500 mA fuse opened

safely in all cases (i.e. without smoke or fire) and ensured Telcordia GR1089 Second level

compliance. There was no damage to the SLIC or even the LCP1521S after the power cross

tests. Although not required by the Telcordia standard, this sort of co-ordination of serial and

parallel protection reduces the system down time and keeps system recovery costs low after

a power cross in the field.

4

Conclusion

The purpose of this application note was to propose a complete protection solution for single

battery voltage SLICs located in remote terminals, at customer premises, in the US.

Therefore, the standard that has been considered for lightning and power crossing tests in

order to validate this protection solution is the Telcordia GR1089 Intrabuilding (equipment

port type 4).

The protection solution consists of programmable overvoltage protection and fuses for

overcurrent protection. The overvoltage protection device is an ST product based on the

crowbar concept (LCP1521S). While the series protection is mainly done using fuses TCP

500 mA from Cooper-Bussman. There is a 10

Ω resistor on each wire that makes the fuses

TCP500mA compatible with the LCP1521S and makes the solution compliant with the

Telcordia GR1089 Intrabuilding standard.

All the tests mentioned in the tables of the Telcordia GR1089 Intrabuilding standard were

performed on the STLC3055N evaluation board shown in Figure 7 on page 8, with both

external fuses and 10

Ω resistors. All test results are available upon request. These results

showed that there was no impact on either of the fuses during lightning tests, while they

opened safely, in time to protect the SLIC and the LCP1521S, during power crossing tests.

The presented protection topology is an effective protection solution for single battery

voltage SLICs located at remote terminals in the US. The application note is intended only

as a guideline. While the STLC3055N is a good example of a single battery voltage SLIC

that one might see in a remote terminal, SLIC designs are excessively variant and therefore

exact implementation of the above circuitry for a different SLIC may or may not be the most

efficient solution.

5

Revision history

Date

Revision

Changes

03-Nov-2006

1

Initial release.