Data Sheet

ADLD8403

MULTITONE POWER RATIO (MTPR)

The DMT signal used in ADSL/ADSL2+ systems carries data in

discrete tones or bins, which appear in the frequency domain in

evenly spaced 4.3125 kHz intervals. In applications using this

type of waveform, the MTPR is commonly used to measure ac

linearity. In general, designers are concerned with two types of

MTPR: in-band and out-of-band. In-band MTPR is the

measured difference from the peak of one tone that is loaded

with data to the peak of an adjacent empty tone. Out-of-band

MTPR is the spurious emissions that occur in bands just below

and above the transmit band. For ADSL2+ applications, the

out-of-band MTPR is the receive band between 25.875 kHz and

138 kHz and the region above 2.208 MHz. Figure 13 shows the

out-of-band MTPR for the ADLD8403.

0

–80

–70

–60

–50

–40

–30

–20

–10

0

0.5

1.0

1.5

2.0

2.5

3.0

FREQUENCY (MHz)

Figure 13. Out-of-Band MTPR

LIGHTNING AND AC POWER FAULT

As an ADSL/ADSL2+ line driver, the ADLD8403 is transformer

coupled to the twisted pair telephone line. In this environment,

the ADLD8403 is subject to large line transients resulting from

events such as lightning strikes or downed power lines. Additional

circuitry is required to protect the ADLD8403 from damage due

to these events.

Rev. C | Page 9 of 10