DS26521 datasheet(70/258 Pages) MAXIM

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DS26521 Single T1/E1/J1 Transceiver

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8.11.2 Transmitter

NRZ data arrives from the framer transmitter; the data is encoded with HDB3 or B8ZS or AMI. The encoded data

passes through a jitter attenuator if it is enabled for the transmit path. A digital sequencer and DAC are used to

generate transmit waveforms complaint with T1.102 and G.703 pulse templates.

A line driver is used to drive an internal matched impedance circuit for provision of 75

Ω, 100Ω, 110Ω, and 120Ω

terminations. The transmitter couples to the E1 or T1 transmit twisted pair (or coaxial cable in some E1

applications) via a 1:2 step-up transformer. For the device to create the proper waveforms, the transformer used

must meet the specifications listed in Table 8-32. The transmitter requires a transmit clock of 2.048MHz for E1 or

1.544MHz for T1/J1 operation.

The DS26521 drivers have a short-circuit and open-circuit detection driver-fail monitor. The TXENABLE pin can

high impedance the transmitter outputs for protection switching. The individual transmitters can also be placed in

high impedance through register settings. The DS26521 also has functionality for powering down the transmitters

individually. The relevant telecommunications specification compliance is shown in Table 8-31.

Table 8-31. Telecommunications Specification Compliance for DS26521 Transmitters

TRANSMITTER FUNCTION

TELECOMMUNICATIONS COMPLIANCE

T1 Telecom Pulse Template Compliance

ANSI T1.403

T1 Telecom Pulse Template Compliance

ANSI T1.102

Transmit Electrical Characteristics for E1 Transmission

and Return Loss Compliance

ITU-T G.703

Table 8-32. Transformer Specifications

SPECIFICATION

RECOMMENDED VALUE

Turns Ratio 3.3V Applications

1:1 (receive) and 1:2 (transmit) ±2%

Primary Inductance

600

μH minimum

Leakage Inductance

1.0

μH maximum

Intertwining Capacitance

40pF maximum

Primary (Device Side)

1.0

Ω maximum

Transmit Transformer DC

Resistance

Secondary

2.0

Ω maximum

Primary (Device Side)

1.2

Ω maximum

Receive Transformer DC

Resistance

Secondary

1.2

Ω maximum

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