TP3410 datasheet(24/32 Pages) NSC

24 / 32 page

Functional Description (Continued)

Deactivation is initiated by writing the DR command in the

Activation Control Register causing ‘‘dea’’e0 to be trans-

mitted towards the NT When the NT ceases to transmit

confirmation of deactivation is provided by a DI Status indi-

cator

117 NT Mode ActivationDeactivation

If activation is initiated by the upstream (LT mode) end with

the NT either powered up or down a Line Signal Detect

Interrupt will be generated on detection of the 10 kHz

‘‘wake-up’’ tone The Activation Indication Register will

show this condition and if the device is powered down the

LSD pin will be pulled low To proceed with the activation

sequence all registers must be programmed appropriately

(see Note 1) and the device must then be powered up The

use of the commands and status indicators is the same

whether activation is initiated locally or in response to the

Line Signal Detect Interrupt An AR command will enable

the device to automatically proceed with the activation se-

quence An internal 15s default timer is also started (in

North America the timer value should be 15 seconds if a

single DSL section is being activated) See TP3410 User’s

Manual for additional information on activation and deacti-

vation

The sequence continues until the NT acquires superframe

synchronization on the SL2 signal received from the LT At

this point an AP Interrupt is generated and the device starts

transmitting SN3 with ‘‘act’’ e 0 To complete activation

normally when the NT has detected INFO3 signals from a

TE the ‘‘act’’ bit must be set e 1 by writing the AC com-

mand to the Activation Control Register An AI Status indi-

cation will finally be generated by the device when the loop

is fully synchronized and receiving SL3 frames with

‘‘act’’e1 this is automatically validated 3 times regardless

of the options selected in Register OPR The loop is then

fully activated with all channels in the data stream available

for use

If activation is not successfully completed before expiry of

the 15s timer the device generates an EI followed by a DI

fault indication and ensures that the Activation Sequencer

returns to the Full Reset state prior to any re-attempt to

activate

Deactivation is normally initiated by the LT which sets

‘‘dea’’e0 towards the NT The TP3410 in NT mode will

detect and validate this bit 3 times prior to setting the DP

interrupt (regardless of the options selected in OPR) Trans-

mission will cease when it is detected that the far-end signal

has ceased after which the device enters the Reset state

and generates a DI Interrupt to indicate that deactivation is

complete

Note 1

The M45 bit conveys an indication of whether the NT can support a

warm-start procedure (the ‘‘cso’’ bit) Since the TP3410 automati-

cally supports both cold and warm start set ‘‘cso’’e0

Applications Information

LINE INTERFACE CIRCUIT

The transmission performance obtainable from a TP3410

U-interface is strongly dependent on the line interface circuit

(LIC) design Two designs shown in

Figures 9 and 10 are

recommended They should be adhered to strictly The

channel response and insertion losses of these circuits

have been carefully designed as an integral part of the over-

all signal processing system to ensure the performance re-

quirements are met under all specified loop conditions De-

viations from these designs may result in sub-optimal per-

formance or even total failure of the system to operate on

some types of loops

The standare LIC

(Figure 9) has the advantage of back-

wards compatibility with Rev 2x devices together with a

generally lower component sensitivity The TP3410 must be

configured to select the chosen LIC For the standard LIC

set saif e 1 in register CR4 This is the default configura-

tion

The alternative LIC

(Figure 10) does not use lineside surge

limiting resistors and so has advantages where line power-

ing is required To configure the TP3410 for the alternative

LIC set saif e 0

Transformer parameters form a major part of the LIC Two

of the most important are

Turns Ratio

Chip side (primary) Line side (secondary)

115

Secondary inductance

LS e 27 mH g5% at 1 kHz

For more details on transformer specification and for a list

of qualified vendors

see the TP3410 User’s Manual

AN-913

BOARD LAYOUT

While the pins of the TP3410 are well protected against

electrical misuse it is recommended that the standard

CMOS practice of applying GND to the device before any

other connections are made should always be followed In

applications where the printed circuit card may be plugged

into a hot socket with power and clocks already present an

extra long ground pin on the connector should be used

Great care must be taken in the layout of the printed circuit

board in order to preserve the high transmission perform-

ance of the TP3410 To maximize performance do not use

the philosophy of separating analog and digital grounds on

the board The 3 GND pins should be connected together

as close as possible to the pins and the 2 VCC pins should

be strapped together All ground connections to each de-

vice should meet at a common point as close as possible to

the 3 GND pins in order to prevent the interaction of ground

return currents flowing through a common bus impedance

A decoupling capacitor of 01 mF should be connected from

this common point to the VCC pins Taking care with the pcb

layout in the following ways will also help prevent noise in-

jection into the receiver front-end and maximize the trans-

mission performance

1 Keep the crystal oscillator components away from the

receiver inputs and use a ground plane for shielding

around these components

2 Keep the connections between the device and the com-

ponents on the Lig inputs short

3 Keep the connections between the device and trans-

former short

ADDITIONAL INFORMATION

For more in-depth information on a variety of applications

the TP3410 Users Manual AN-913 is a comprehensive

guide to the hardware and software required to meet the

ANSI interface specification

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