AFE1302

11

SBWS014

ADSL FRONT-END SYSTEM PERFORMANCE

PARAMETER

CONDITIONS

VALUE

UNITS

TX PATH

Peak Signal Amplitude to Telephone Line

12

Vp-p

Load Impedance

100

Ω

Output Power

To Line (100

Ω Match)

13

dBm

Low-Pass Filter Corner Frequency

127

kHz

Passband Ripple

3dB

Group Delay Variation

15

ms

Output Noise, Out of Band

See Note (2)

–142

dBm/Hz

RX PATH

RX Input

12.5

Vp-p

MTPR

70

dB

Noise Floor

PGA = 40dB

–142

dBm/Hz

External High-Pass Filter Corner Frequency

157

kHz

Anti-Alias Filter Corner Frequency

1.1

MHz

Passband Ripple

3dB

NOTE: (1) dBm referenced from average tone power and spread over 4kHz receive tone bins. (2) Measured at 200kHz with typical ADSL multitone transmission signal.

TABLE VIII. ADSL Front-End System Performance when using the AFE1302 in a Texas Instruments Reference Design

Evaluation Board. Typical at 25

°C, AV

measured at line side.

The specifications for the complete system solution are given

in Table VIII. The numbers include the effects of both the

AFE1302 and the surrounding external components, includ-

ing a Burr-Brown TX line driver from Texas Instruments.

RECEIVE

Receive channel external components include a hybrid, receive

amplifier, fifth-order high-pass passive filter, and first-order,

low-pass, anti-alias filter. The ADSL system is frequency

division multiplexed on a single twisted pair. Filters are used to

separate the transmit and receive signals. When the AFE1302

drives long twisted-pair loops, the transmit signal is much

larger than the receive signal. The hybrid will ideally eliminate

all of the transmit signal at the receive input. However, for

poorly matched lines, the actual reduction may be quite small.

Without external filtering between the transmit output and the

receive input, the transmit signal will clip the receive input

before the on-chip receive filter can reduce the transmit signal.

Therefore, external receive filters are required to eliminate

transmit noise. Refer to Figure 6 for an external circuit and

contact the factory for a detailed reference design document.