Exar XRT83SL38/L38EVAL, Руководство пользователя

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XRT83SL38/L38EVAL User Manual
Page 4 of 23
External Impedance Mode (T1/J1, 1.544MHz, 100ohm/110ohm)
The XRT83SL38/L38EVAL can be programmed for external impedance mode through the
microprocessor interface. For T1 applications, two 3.1ohm resistors are necessary on the
transmit outputs of the LIU. A 100ohm resistor is necessary on the receiver inputs. (Note: These
values do not change when using either a 1:2 or 1:2.45 turns ratio on the transmit side) Figure 4
is a simplified block diagram of the external mode for T1 applications.
3.1
3.1
Line Interface Module
TTIP
TRING
RTIP
RRING
XRT83SL38/L38 LIU
100
1:2
1:1
Figure 4 Simplified Block Diagram of the External Mode, T1/J1
External Impedance Mode (E1, 2.048MHz, 75ohm or 120ohm)
The XRT83SL38/L38EVAL can be programmed for external impedance mode through the
microprocessor interface. For E1 applications, two 9.1ohm resistors are necessary on the
transmit outputs of the LIU. A 75ohm or 120ohm resistor is necessary on the receiver inputs.
(Note: The resistor values on the transmit side change to 6.2ohms when using a 1:2.45 turns
ratio) Figure 5 is a simplified block diagram of the external mode for E1 applications.
9.1
9.1
Line Interface Module
TTIP
TRING
RTIP
RRING
75 (for 75ohm Termination)
120 (for 120ohm Termination)
XRT83SL38/L38 LIU
1:2
1:1
Figure 5 Simplified Block Diagram of the External Mode, E1 75ohm and 120ohm