POWER AND LINEAR IC SOLUTIONS
Triple Play, VoIP, Require Special Protection 
Thyristors and resettable fuses may be used

Customer Premises Equipment (CPE) for VoIP and triple-play applications presents a relatively complex design challenge when specifying circuit protection because every port must be protected in line with EN60950. Bourns can supply appropriate devices for all of the common variations within such CPE.



The CPE will take in a high speed data carrier such as ADSL2+ input; outputs are typically to two analogue voice lines (VoIP), a LAN router port and Video (SCART) interface. There may also be a USB port for a printer or shared HDD or WLAN.

The ADSL2+ input has an outside line and must be protected against external risks such as lightning strikes or contact with power lines. The relevant tests are described in TIA-968-A and EN60950.

Bourns offers a wide range of protection for Over Current Protection (OCP) and Over voltage Protection (OVP), including Telefuse, LPM and Multifuse for OCP and gas tubes, TISP (Thyristor), TVS diodes and TVS diode arrays for OVP. The xDSL protection will contain a Telefuse (B1250T) and a TISP (TISP4C350H3BJR-S). Bourns can also offer suitable transformers for the xDSL chipset.

The voice ports employ Subscriber Line Interface Circuits (SLICs) that include DC voltages with magnitudes as high as 50V as well as 16Hz ringing voltages up to 120V peak. These therefore need a special thyristor protector.

Field experience shows that protection is required on such a line on CPE even within a building, since the equipment is sensitive to over voltage events such as nearby lighting strikes. The TISP61089BDR-S is a double-programmable protector to serve both Tip and Ring on each line and is referenced to the negative battery supply of the SLIC. If the application has a positive and negative battery supply, other solutions may be required: for instance the TISP9110LDMR-S.

This application also needs to have OCP that is resettable on each wire, for instance the MF-SM013/250V Polymer PTC (Positive Temperature Coefficient) fuse. With this solution the voice ports will meet the Telcordia GR-1089 issue 3 intrabuilding specification and ITU-T K.20 (Basic).

The level of protection for USB is mainly for ESD using a TVS-Array (CDSOT23-SR208) together with a Multifuse (MF-NSMF110-2) as OCP on the power feed.

Video output would be well protected with the Bourns Chipguard (MLC) series, a low capacitive multilayer varistor. The 9V DC input needs protection from transients with a TVS diode (CD214-12ALF).

Circuit protection products
  • Gas discharge tubes
  • MSP hybrid protectors
  • Signal and dataline protectors
  • Multifuse polymer PTC resettable fuses
  • Line protection modules
  • Telefuse telecom fuses
  • ChipGuard ESD protectors
  • Transient Voltage suppression (TVS) diodes
  • TISP thyristor surge protectors

Applications
  • Customer Premises Equipment
  • Triple-play terminal adapters
  • Central office equipment
  • Access equipment

For further information, including Datasheets and information on how to obtain Samples, please click here.