Thyristors protect SLIC interfaces from power fault events

15th March 2017
Alice Matthews

Two series of SIDACtor protection thyristors have been introduced by Littelfuse, designed to protect SLIC (Subscriber Line Interface Circuit) interfaces against lightning-induced surges and power fault events. The surface-mount B61089QDR and B9110DF series thyristors for programmable tracking protection contain fast-switching crowbarring structures that are compatible with the basic levels outlined in the ITU K.20, K.21 and K.45 recommendations from the International Telecommunications Union (ITU).

The B61089QDR dual-port battrax provides surge protection for SLIC cards that have only implemented negative voltage ringing. The B9110DF series provides surge protection for SLIC cards that have implemented both positive and negative voltage ringing, which are used in most telecommunications applications today. It also tracks the Vcc reference of the SLIC chipset so that if/when it enters a low quiescent stage, the protection threshold will match this lower threshold.

Applications for the B61089QDR and B9110DF series include protection for:

  • Wireless in the Local Loop (WLL) systems
  • Voice applications that require regenerated POTS (Plain Old Telephone Service) signals
  • Voice over IP (VoIP) applications
  • Private Branch Exchange (PBX) systems
  • Foreign Exchange Station (FXS) applications
  • Digital Pair Gain systems (DPG)
  • Digital Loop Carrier (DLC) systems
  • Small Office, Home Office (SOHO) systems.

“The B61089QDR and B9110DF Series provide crowbarring power fault protection at levels far superior to the typical clamping device,” said Jeff Chin, Product Line Director for SIDACtor Protection Thyristors at Littelfuse. “They combine superior surge protection performance with a low switching threshold and low on-state voltage to ensure better protection.”

Key features:

  • High performance protection for SLICs with +VBAT and –VBAT references for the B9110DF Series and –VBAT reference for the B61089QDR Series and with changing VBAT references.
  • Prevent component property degradation after multiple surge events within the rated limits, thereby extending equipment lifetime.
  • Help line drivers comply with global standards because these devices are certified, environmentally friendly and suitable for worldwide usage.

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