Datasheet

DS26514 4-Port T1/E1/J1 Transceiver
19-5856; Rev 4; 5/11 85 of 305
9.12 Line Interface Units (LIUs)
The DS26514 has four identical LIU transmit and receive front-ends for each of the four framers. Each LIU contains
three sections: the transmitter, which waveshapes and drives the network line; the receiver, which handles clock
and data recovery; and the jitter attenuator. The DS26514 LIUs can switch between T1 or E1 networks without
changing any external components on either the transmit or receive side.
Figure 9-21 shows a recommended
circuit for software selected termination with protection. In this configuration the device can connect to 100Ω T1
twisted pair, 110Ω J1 twisted pair, 75Ω or 120Ω E1 twisted pair without additional component changes. The signals
between the framer and LIU are not accessible by the user, thus the framer and LIU cannot be separated. The
transmitters have fast high-impedance capability and can be individually powered down.
The DS26514’s transmit waveforms meet the corresponding G.703 and T1.102 specifications. Internal software-
selectable transmit termination is provided for 100Ω T1 twisted pair, 110Ω J1 twisted pair, 120Ω E1 twisted pair
and 75Ω E1 coaxial applications. The receiver can connect to 100Ω T1 twisted pair, 110Ω J1 twisted pair, 120Ω E1
twisted pair, and 75Ω E1 coaxial. The receive LIU can function with a receive signal attenuation of up to 36dB for
T1 mode and 43dB for E1 mode. The receiver sensitivity is programmable from 12dB to 43dB of cable loss. Also a
monitor gain setting can be enabled to provide 14dB, 20dB, 26dB, and 32dB of resistive gain.