AD8016ARE Analog Devices Inc, AD8016ARE Datasheet - Page 12

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AD8016ARE

Manufacturer Part Number
AD8016ARE
Description
IC AMP XDSL LINE DVR 28-TSSOP
Manufacturer
Analog Devices Inc
Type
Driverr
Datasheet

Specifications of AD8016ARE

Rohs Status
RoHS non-compliant
Number Of Drivers/receivers
2/0
Protocol
xDSL
Voltage - Supply
3 V ~ 13 V
Mounting Type
Surface Mount
Package / Case
28-TSSOP Exposed Pad, 28-eTSSOP, 28-HTSSOP
Power Supply Requirement
Dual
Package Type
TSSOP EP
Slew Rate
1000V/us
Pin Count
28
Lead Free Status / RoHS Status
Not Compliant
BIAS pin (I
down I
down resistor to ground or a current sink attached to the BIAS
pin can be used to set I
BIAS pin may be used in combination with the PWDN1 and
PWDN0 pins; however, diminished MTPR performance may
result when I
the BIAS pin shunts away a portion of the internal bias current.
Setting PWDN1 or PWDN0 to Logic 0 also shunts away a
portion of the internal bias current. The reduction of quiescent
bias levels due to the use of PWDN1 and PWDN0 is consistent
with the percentages established in Table II. When PWDN0 alone
is set to Logic 0, and no other means of reducing the internal
bias currents is used, full-rate ADSL signals may be driven while
maintaining reasonable levels of MTPR.
THERMAL SHUTDOWN
The AD8016ARB and AD8016ARP have been designed to
incorporate shutdown protection against accidental thermal
overload. In the event of thermal overload, the AD8016 was
designed to shut down at a junction temperature of 165°C and
return to normal operation at a junction temperature 140°C.
The AD8016 continues to operate, cycling on and off, as long as
the thermal overload condition remains. The frequency of the
protection cycle depends on the ambient environment, severity
of the thermal overload condition, the power being dissipated,
and the thermal mass of the PCB beneath the AD8016. When
the AD8016 begins to cycle due to thermal stress, the internal
shutdown circuitry draws current out of the node connected in
common with the BIAS pin, while the voltage at the BIAS pin
goes to the negative rail. When the junction temperature returns
to 140°C, current is no longer drawn from this node, and the
BIAS pin voltage returns to the positive rail. Under these cir-
cumstances, the BIAS pin can be used to trip an alarm indicat-
ing the presence of a thermal overload condition.
Figure 39 also shows three circuits for converting this signal to a
standard logic level.
AD8016
BIAS
Q
10k
is less than 1 mA total. Alternatively, an external pull-
Figure 38. Logic Drive of BIAS Pin for
Complete Amplifier Shutdown
200 A
PWDN0
Figure 39. Shutdown and Alarm Circuit
BIAS
Q
SGS–THOMSON
1/4 HCF 40109B
V
V
is lowered too much. Current pulled away from
CC
3.3V LOGIC
CC
) and the supply current (I
*
PWDN1
R1 = 47k
R1 = 22k
5V
10k
AD8016
ALARM
DOWN
SHUT-
BIAS
Q
FOR
FOR
to lower levels (see Figure 39). The
50k
R2
6V
12V
V
EE
OR
S
.
S
OR +12V
2N3904
V = V
BIAS
BIAS
R1
*
S
CC
,
– 0.2V
Q
100k
1M
). A typical shut-
BIAS
OR
10k
0 A–200 A
5V
MIN
ALARM
350
–12–
APPLICATIONS
The AD8016ARP and AD8016ARB dual xDSL line driver
amplifiers are the most efficient xDSL line drivers available on
the market today. The AD8016 may be applied in driving modu-
lated signals including discrete multitone (DMT) in either
direction; upstream from CPE to the CO and downstream from
CO to CPE. The most significant thermal management chal-
lenge lies in driving downstream information from CO sites to
the CPE. Driving xDSL information downstream suggests the
need to locate many xDSL modems in a single CO site. The
implication is that several modems will be placed onto a single
printed circuit board residing in a card cage located in a variety
of ambient conditions. Environmental conditioners such as fans
or air conditioning may or may not be available, depending on
the density of modems and the facilities contained at the CO site.
To achieve long-term reliability and consistent modem perfor-
mance, designers of CO solutions must consider the wide array
of ambient conditions that exist within various CO sites.
MULTITONE POWER RATIO OR MTPR
ADSL systems rely on discrete multitone modulation to carry
digital data over phone lines. DMT modulation appears in the
frequency domain as power contained in several individual
frequency subbands, sometimes referred to as tones or bins, each
of which is uniformly separated in frequency. (See Figure 1 for
an example of downstream DMT signals used in evaluating
MTPR performance.) A uniquely encoded, quadrature amplitude
modulation (QAM) signal occurs at the center frequency of
each subband or tone. Difficulties arise when decoding these
subbands if a QAM signal from one subband is corrupted by the
QAM signal(s) from other subbands, regardless of whether
the corruption comes from an adjacent subband or harmonics
of other subbands. Conventional methods of expressing the
output signal integrity of line drivers, such as spurious-free
dynamic range (SFDR), single-tone harmonic distortion or
THD, two-tone intermodulation distortion (IMD), and third-
order intercept (IP3) become significantly less meaningful when
amplifiers are required to drive DMT and other heavily modulated
waveforms. A typical xDSL downstream DMT signal may
contain as many as 256 carriers (subbands or tones) of QAM
signals. MTPR is the relative difference between the mea-
sured power in a typical subband (at one tone or carrier)
versus the power at another subband specifically selected to
contain no QAM data. In other words, a selected subband (or
tone) remains open or void of intentional power (without a
QAM signal), yielding an empty frequency bin. MTPR, some-
times referred to as the empty bin test, is typically expressed
in dBc, similar to expressing the relative difference between
single-tone fundamentals and second or third harmonic dis-
tortion components.
See Figure 1 for a sample of the ADSL downstream spectrum
showing MTPR results while driving 20.4 dBm of power onto a
100 Ω line. Measurements of MTPR are typically made at the
output (line side) of ADSL hybrid circuits. (See Figure 46a for
an example of Analog Devices’ hybrid schematic.) MTPR can
be affected by the components contained in the hybrid circuit,
including the quality of the capacitor dielectrics, voltage ratings,
and the turns ratio of the selected transformers. Other compo-
nents aside, an ADSL driver hybrid containing the AD8016 can be
optimized for the best MTPR performance by selecting the turns
ratio of the transformers. The voltage and current demands from
the differential driver changes, depending on the transformer
REV. B

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