Datasheet

DS26502
77 of 125
13. LINE INTERFACE UNIT (LIU)
The LIU in the DS26502 contains three sections: the receiver, which handles clock and data recovery; the
transmitter, which generates waveshapes and drives the network line; and the jitter attenuator. These three
sections are controlled by the line interface control registers (LIC1–LIC4), which are described below.
The DS26502 can switch among T1, J1, E1, and 6312kHz without changing any external circuits. A
different transformer is used for 64KCC networks. For a list of recommended transformer part numbers,
contact technical support at www.maxim-ic.com/support. Figure 13-1 shows a network connection using
minimal components. In this configuration the DS26502, using a fixed 120Ω external termination, can
connect to T1, J1, E1, 64KCC, or 6312kHz. The receiver can adjust the 120Ω termination to 100Ω, 110Ω
or 75Ω. The transmitter can adjust its output impedance to provide high return loss characteristics for
75Ω, 100Ω, 110Ω, and 120Ω lines. Other components may be added to this configuration to meet safety
and network protection requirements. This is covered in the Recommended Circuits section (Section
13.8).
Figure 13-1. Basic Network Connection
TTIP
TRING
RTIP
RRING
DS26502
TRANSMIT
LINE
RECEIVE
LINE
10
μ
F
60 60
0.01
μ
F
BACKPLANE
CONNECTIONS
1:1
2:1