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AFE1105E Schematic ( PDF Datasheet ) - Burr-Brown Corporation

Teilenummer AFE1105E
Beschreibung HDSL/MDSL ANALOG FRONT END
Hersteller Burr-Brown Corporation
Logo Burr-Brown Corporation Logo 




Gesamt 10 Seiten
AFE1105E Datasheet, Funktion
® AFE1105
AFE1105
HDSL/MDSL ANALOG FRONT END
FEATURES
q COMPLETE ANALOG INTERFACE
q T1, E1, AND MDSL OPERATION
q CLOCK SCALEABLE SPEED
q SINGLE CHIP SOLUTION
q +5V ONLY (5V OR 3.3V DIGITAL)
q 250mW POWER DISSIPATION
q 48-PIN SSOP
q –40°C TO +85°C OPERATION
DESCRIPTION
Burr-Brown’s Analog Front End greatly reduces the
size and cost of an HDSL or MDSL system by provid-
ing all of the active analog circuitry needed to connect
the Metalink MtH1210B HDSL digital signal proces-
sor to an external compromise hybrid and a 1:2.3
HDSL line transformer. All internal filter responses as
well as the pulse former output scale with clock
frequency—allowing the AFE1105 to operate over a
range of bit rates from 196kbps to 1.168Mbps.
Functionally, this unit is separated into a transmit and
a receive section. The transmit section generates, fil-
ters, and buffers outgoing 2B1Q data. The receive
section filters and digitizes the symbol data received
on the telephone line and passes it to the MtH1210B.
The HDSL Analog Interface is a monolithic device
fabricated on 0.6µCMOS. It operates on a single +5V
supply. It is housed in a 48-pin SSOP package.
Pulse
Former
Line
Driver
txLINEP
txLINEN
PLLOUT
PLLIN
txDAT
txCLK
rxSYNC
rxLOOP
rxGAIN
rxD13 - rxD0
2
14
Transmit
Control
Receive
Control
Decimation
Filter
Voltage
Reference
REFP
VCM
REFN
Delta-Sigma
Modulator
rxLINEP
rxLINEN
rxHYBP
rxHYBN
Patents Pending
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111
Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1996 Burr-Brown Corporation
PDS-1346
Printed in U.S.A. September, 1996






AFE1105E Datasheet, Funktion
THEORY OF OPERATION
The transmit channel consists of a switched-capacitor pulse
forming network followed by a differential line driver. The
pulse forming network receives symbol data from the
XMTDA output of the MtH1210B and generates a 2B1Q
output waveform. The output meets the pulse mask and
power spectral density requirements defined in European
Telecommunications Standards Institute document RTR/
TM-03036 for E1 mode and in sections 6.2.1 and 6.2.2.1 of
Bellcore technical advisory TA-NWT-001210 for T1 mode.
The differential line driver uses a composite output stage
combining class B operation (for high efficiency driving
large signals) with class AB operation (to minimize cross-
over distortion).
The receive channel is designed around a fourth-order delta
sigma A/D converter. It includes a difference amplifier
designed to be used with an external compromise hybrid for
first order analog crosstalk reduction. A programmable gain
amplifier with gains of 0dB to +9dB is also included. The
delta sigma modulator operating at a 24X oversampling ratio
produces 14 bits of resolution at output rates up to 584kHz.
The basic functionality of the AFE1105 is illustrated in
Figure 1 shown below.
The receive channel operates by summing the two differen-
tial inputs, one from the line (rxLINE) and the other from the
compromise hybrid (rxHYB). The connection of these two
inputs so that the hybrid signal is subtracted from the line
signal is described in the paragraph titled “Echo Cancella-
tion in the AFE”. The equivalent gain for each input in the
difference amp is 1. The resulting signal then passes to a
programmable gain amplifier which can be set for gains of
0dB through 9dB. The ADC converts the signal to a
14-bit digital word, rxD13-rxD0.
rxLOOP INPUT
rxLOOP is the loopback control signal. When enabled, the
rxLINEP and rxLINEN inputs are disconnected from the
AFE. The rxHYBP and rxHYBN inputs remain connected.
Loopback is enabled by applying a positive signal (Logic 1)
to rxLOOP.
ECHO CANCELLATION IN THE AFE
The rxHYB input is designed to be subtracted from the
rxLINE input for first order echo cancellation. To accom-
plish this, note that the rxLINE input is connected to the
same polarity signal at the transformer (positive to positive
and negative to negative) while the rxHYB input is con-
nected to opposite polarity through the compromise hybrid
(negative to positive and positive to negative) as shown in
Figure 2.
RECEIVE DATA CODING
The data from the receive channel A/D converter is coded in
two’s complement code.
ANALOG INPUT
Positive Full Scale
Mid Scale
Negative Full Scale
OUTPUT CODE (rxD13 - rxD0)
01111111111111
00000000000000
10000000000000
RECEIVE CHANNEL PROGRAMMABLE
GAIN AMPLIFIER
The gain of the amplifier at the input of the Receive Channel
is set by two gain control pins, rxGAIN1 and rxGAIN0. The
resulting gain between 0dB and +9dB is shown below.
rxGAIN1
0
0
1
1
rxGAIN0
0
1
0
1
GAIN
0dB
3.25dB
6dB
9dB
txDAT
Pulse Former
Differential
Line Driver
14
rxD13 - rxD0
ADC
Programmable
Gain Amp
Difference
Amplifier
FIGURE 1. Functional Block Diagram of AFE1105.
®
AFE1105
6
txLINEP
txLINEN
rxHYBP
rxHYBN
rxLINEP
rxLINEN

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