DS2153, DS2154 Selectable 120

通信设计应用

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描述

Abstract: Different values of resistor can be selected between DS2153 or DS2154 single chip transceiver (SCT) and the transformer when interfacing to the E1 line with secondary overvoltage protection or in a high return loss configuration.

When interfacing to the E1 line with Secondary Over Voltage protection or in a high return loss configuration, resistors are added between the DS2153 outputs and the transformer. Normally the resistors are of different values depending on whether the interface is driving a 75Ω coax or 120Ω twisted wire pair line. Also a change in the termination resistor is required. A single set of resistors can be utilized in both situations by using the circuit shown in Figure 1. The dotted lines indicate jumper positions for selecting 75Ω or 120Ω operation.

I
Figure 1. E1 interface.

Table 1. Line Interface Control Register Settings
Line Type L2 L1 L0
75Ω 0 1 0
120Ω 0 1 0

Notes:

  1. Transformers shown are available from Pulse.
  2. Resistors shown are within 1" of best value.


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