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STLC60135

ADSL MODEM CHIP SET

STMicroelectronics 

TOSCA STLC60134/STLC60135

Analog Front End (STLC60134)

HCMOS5A (0.5µm) mixed digital and analog

technology has been chosen to produce this

component that embodies the analog functions of

the TOSCA. Automatic gain control amplifiers,

placed at the analog functions of the TOSCA.

Automatic gain control amplifiers, placed at the

analog interface of transmit and receive paths, al-

low for line’s high attenuation in order to keep ac-

ceptable noise level of the signal ADC’s and

DAC’s resolution, that is 12-bit wide with 8.8MHz

sampling rate. Thanks to the symmetrical archi-

tecture the same channel filter can be used as a

part of either the upstream or the downstream

path: ATU-C or ATU-R end.

A built-in driver allows for single external clock

generation using a XTAL (ATU-C) or a VCXO

(ATU-R).

STLC60134 Analog Front End’s main features:

Rx automatic gain control: 0-31dB in 1dB

steps

Two input ports allow selection of RX signals,

e.g. with or without external attenuation

Second transmit port available (i.e. echo can-

cellation)

Programmable low pass and band pass filters

12-bit DAC and ADC, sampling at 8.832MHz

Xtal: 35.328MHz, ±50ppm, the accuracy of the

frequency is determined by the External XTAL

Direct connection to STLC60135 DTM modem

Error correction on ADC output

Test interface for digital and analog sections

Analog and digital loop back modes

Figure 3. DMT Modem block diagram.

Single 3.3V supply, or 3.3V analog and 3.0V

digital supplies

Power dissipation 0.4W

Power-down mode 0.1W

TQFP-64 (10 x 10mm body, 0.5mm pitch)

Discrete MultiTone Digital Modem (STLC60135)

The DMT modem has been developed in

HCMOS6 (0.35µm) technology.

It performs PMD (Physycal Medium Dependant)

sub-layer and TC (Transmission Convergence)

sub-layer functions. In other words we can think

to split up the chip into two separate blocks: the

first one which carries out modem functions

(PMD sub layer) and a second one in charge of

ATM framing.

The chip is controlled and programmed by an ex-

ternal processor and is seen as a memory

mapped device.

MODEM Functions

The modem part of the chip includes all the nec-

essary blocks needed for digitally DMT mapping

and demapping. A 14-bit code for every carrier al-

lows constellations with up to 16383 points.

Internally digital filters carry out Time Equalization

to reduce the effects of the inter symbol inter-

faces. That is followed by Fast Fourier Transform

(in transmit direction an Inverse FFT is per-

formed) in order to change from time domain to

frequency domain. Afterwards a Frequency

Equalization cuts down carrier by carrier the

channel distortion; signal’s amplitude attenuation

and phase rotation. By efficient algorithms, this

Rx

DSP FE

ADSL

AFE

Tx

DSP FE

FFT

DEMAPPER

VITERBI

SIGNAL

MONITORING &

FEQ UPDATE &

DPLL

PMD SUBLAYER

IFFT

MAPPER

VITERBI

D98TL406

R/S

DECODER

DE-

FRAMER

CELL

BASED

FUNCT.

TC SUBLAYER

R/S

CODER

FRAMER

CELL

BASED

FUNCT.

Rx

INTERF.

INTERLEAVED

FAST

ATM (UTOPIA)

Tx

INTERF.

FAST

INTERLEAVED

3/7

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