Trunk Interface 8-Pin Mini-PDIP

The circuit provides DC loop termination for analog trunk lines. The V-I characteristics is equivalent to a fixed voltage drop (zener like characteristic) in series with an external resistance that determines the slope of the DC characteristic. An external low voltage electrolytic capacitor causes the circuit to exhibit a very high impedance to all AC signal above a minimum frequency that is determined by the capacitor itself and by a 20 K nominal resistor integrated on the chip. The Off-Hook status is detected all the time a typic of 8 mA is flowing into the circuit. In this condition a constant current generator is activated to supply an external device (typically an optocoupler) without affecting the AC characteristic of the circuit. When Pulse Dialing is required the PULSE input (pin 3) connected to V- causes the device to reduce the fixed DC voltage drop and to exhibit a pure resistive impedance equal to the external resistor.

• ON CHIP POLARITY GUARD
• MEETS DC LINE CHARACTERISTICS OF EITHER CCITT AND EIA RS 464 SPECS
• PULSE FUNCTION
• HIGH AC IMPEDANCE
• OFF HOOK-STATUS DETECTION OUTPUT
• LOW EXTERNAL COMPONENT COUNT