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MH88437AS-PI Datasheet(PDF) 3 Page - Mitel Networks Corporation |
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MH88437AS-PI Datasheet(HTML) 3 Page - Mitel Networks Corporation |
3 / 16 page Advance Information MH88437-P 3 20,23 26 IC Internal Connection. No connection should be made to this pin externally. 21,22 SC Short Circuit. These two pins should be connected to each other via a 0 Ω link. 24 VLOOP2 Loop Voltage Control Node 2. Used to set DC termination characteristics. 25 VLOOP1 Loop Voltage Control Node 1. Used to set DC termination characteristics. 27 RING Ring Lead. Connects to the “Ring” lead of the telephone line. 28 TIP Tip Lead. Connects to the “Tip” lead of the telephone line. Pin Description (continued) Pin # Name Description Functional Description The device is a Data Access Arrangement (D.A.A.). It is used to correctly terminate a 2-Wire telephone line. It provides a signalling link and a 2-4 Wire line interface between an analog loop and subscriber data transmission equipment, such as Modems, Facsimiles (Fax’s), Remote Meters, Electronic Point of Sale equipment and Set Top Boxes. Isolation Barrier The device provides an isolation barrier capable of meeting the supplementary barrier requirements of the international standard IEC 950 and the national variants of this scheme such as EN 60950 for European applications and UL 1950 for North American applications. External Protection Circuit An External Protection Circuit assists in preventing damage to the device and the subscriber equipment, due to over-voltage conditions. See Application Note MSAN-154 for recommendations. Suitable Markets The MH88437 has features such as programmable line and network balance impedance, programmable DC termination and a supplementary isolation barrier. For countries that do not need to meet the French and German requirements there is a pin for pin compatible device the MH88435. There are, however, a small number of countries with a 100M Ω leakage requirement that this device does not meet. These are Belgium, Greece, Italy, Luxembourg, Spain and Poland. Although Luxembourg will now accept TBR21 and there are exceptions to the Italian specification, in most applications the MH88437 will comply with Luxembourg and Italian specifications. For approval in Denmark and Sweden the TRB21 route is recommended. Approval specifications are regularly changing and the relevant specification should always be consulted before commencing design. Line Termination When Loop Control (LC) is at a logic 1, a line termination is applied across Tip and Ring. The device can be considered off-hook and DC loop current will flow. The line termination consists of both a DC line termination and an AC input impedance. It is used to terminate an incoming call, seize the line for an outgoing call, or if it is applied and disconnected at the required rate, can be used to generate dial pulses. The DC termination resembles approximately 300 Ω resistance, which is loop current dependent. Furthermore, it can be programmed to meet different national requirements. For normal operation VLOOP3 should be open circuit and a resistor (R2) should be fitted between VLOOP1 and VLOOP2, as shown in Figure 4. The approval specification will give a DC mask characteristic that the equipment will need to comply to. The DC mask specifies the amount of current the DAA can sink for a given voltage across tip and ring. Graph 1 shows how the voltage across tip and ring varies with different resistors (R2) for a given loop current. Network Balance The network balance impedance of the device can be programmed by adding external components By |
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