PBL38772/1SOD 데이터 시트보기 (PDF) - Ericsson

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PBL38772/1SOD

Subscriber Line Interface Circuit (SLIC)

Ericsson  

PBL 387 72

Functional Description and Applications Information

Introduction

The Figure 8 diagram shows the PBL 387 72/1 in a typical

application with a non-programmable, Combo I, codec. The

PBL 387 72/1 can equally well be used with programmable

codecs. This SLIC is suitable in short loop power sensitive

application like, Cable modem, Voice over DSL, ISDN terminal

adapter (NT1+), Voice over IP, Integrated Access Device

(IAD), Residential Gateway or other short loop application.

The component values chosen for the application diagram

example yield a two-wire impedance of 600 Ω, resistive.

The balance resistor is calculated for line impedance, ZL

(compromise impedance), of 600 Ω, resistive. The two-wire to

four-wire gain is set by RTX and RFB to produce the digital mW

level at the PCM transmit bus.

RF1, RF2 and the clamp “OVP” make up the overvoltage

protection network.

The ratio between RFB and RTX sets the transmit gain.

CTC and CRC clamp fast transients that may bypass the

OVP clamp and also filter high frequency

interference (RFI filter).

CHP and CLP are coupling capacitors within two SLIC

feedback loops that control SLIC battery feed

and SLIC voice frequency transmission.

CTB, CB, CVCC are power supply bypass capacitors.

DTB

is a diode that is part of the battery switching

function.

DB

prevents reverse currents from the VB supply

rail during application of negative over

voltages.

DBB

RT

RRX

RLD

RLC

RREF

RRT

CRING

VTB

VB

is normally reverse biased, but conducts

supply VTB to the VBAT terminal in case the

voltage VB would fail.

sets the two-wire impedance (note that RT may

be replaced with a complex impedance, ZT, to

implement complex terminating impedance).

sets the receive gain.

sets the loop current detector threshold.

sets the constant dc loop current.

sets a SLIC reference current (must be 15.0 kΩ,

1%, as specified).

sets the ring trip loop current detector

threshold.

is used for the high voltage ringing signal AGC

(automatic gain control) function.

is the talk battery supply, i.e. the negative

supply voltage that sources the loop current.

is the ringing battery, i.e. the negative supply

voltage that is used to power the SLIC, while

ringing the line. This battery is also used to

provide on-hook voltage.

Design supporting tools

The following supporting tools are available for the

PBL 387 72/1:

- Test board, TB 215

- Pspice model PBL 387 72/1

10

EN/LZT 146 136 R1A © Ericsson Microelectronics, December 2001

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