Data Sheet ADLD8403
Rev. D | Page 9 of 10
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.
08848-019
0
–80
–70
–60
–50
–40
–30
–20
–10
0 0.5 1.0 1.5 2.0
2.5 3.0
OUTPUT POWER (dBm/Hz)
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.
