AD8016ARBZ Analog Devices Inc, AD8016ARBZ Datasheet - Page 13

• Manufacturer Part Number: AD8016ARBZ
• Description: IC,Operational Amplifier,DUAL,BIPOLAR,SOP,24PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Type: Driverr

Specifications of AD8016ARBZ

• Number Of Drivers/receivers: 2/0
• Protocol: xDSL
• Voltage - Supply: 3 V ~ 13 V
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (7.5mm Width) Fused Leads
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: AD8016ARB-EVAL - BOARD EVAL FOR AD8016ARB
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

turns ratio. The point on the curve indicating maximum dynamic
headroom is achieved when the differential driver delivers both
the maximum voltage and current while maintaining the lowest
possible distortion. Below this point, the driver has reserve
current-driving capability and experiences voltage clipping.
Above this point, the amplifier runs out of current drive capabil-
ity before the maximum voltage drive capability is reached.
Since a transformer reflects the secondary load impedance back
to the primary side by the square of the turns ratio, varying the
turns ratio changes the load across the differential driver. In the
transformer configuration of Figure 46a and 46b, the turns ratio
of the selected transformer is effectively doubled due to the
parallel wiring of the transformer primaries within this ADSL
driver hybrid. The following equation may be used to calculate
the load impedance across the output of the differential driver,
reflected by the transformers, from the line side of the xDSL
driver hybrid. Z' is the primary side impedance as seen by the
differential driver; Z
former turns ratio.
Figure 40 shows the dynamic headroom in each subband of a
downstream DMT waveform versus turns ratio running at 100%
and 60% of the quiescent power while maintaining –65 dBc of
MTPR at V
Once an optimum turns ratio is determined, the amplifier has an
MTPR performance for each setting of the power-down pins.
The table below demonstrates the effects of reducing the total
power dissipated by using the PWDN pins on MTPR perfor-
mance when driving 20.4 dBm downstream onto the line with a
transformer turns ratio of 1:1.4.
PWDN1
1
1
0
0*
*This mode is quiescent power dissipation.
REV. B
Figure 40. Dynamic Headroom vs. XFMR Turns Ratio,
V
S
= ± 12 V
–1
–2
4
3
2
1
0
Table III. Dynamic Power Dissipation for
Downstream Transmission
1.0
V
PWDN1, PWDN0 = (1,1)
S
S
=
= ± 12 V.
1.1
12V
1.2
PWDN0
1
0
1
0
2
is the line impedance and N is the trans-
DOWNSTREAM TURNS RATIO
1.3
Z
V
PWDN1, PWDN0 = (1,1)
S
' ≡
1.4
=
V
PWDN1, PWDN0 = (1,0)
(
11.4V
S
2
=
1.5
×
Z
11.4V
2
N
V
PWDN1, PWDN0 = (1,0)
1.6
S
)
2
PD (W)
1.454
1.262
1.142
0.120
=
12V
1.7
1.8
1.9
MTPR
–78 dBc
–75.3 dBc
–57.2 dBc
N/A
2.0
–13–
GENERATING DMT
At this time, DMT modulated waveforms are not typically menu-
selectable items contained within arbitrary waveform generators.
Even using AWG software to generate DMT signals, AWGs that
are available today may not deliver DMT signals sufficient in
performance with regard to MTPR due to limitations in the D/A
converters and output drivers used by AWG manufacturers.
Similar to evaluating single-tone distortion performance of an
amplifier, MTPR evaluation requires a DMT signal generator
capable of delivering MTPR performance better than that of the
driver under evaluation. Generating DMT signals can be accom-
plished using a Tektronics AWG 2021 equipped with opt 4,
(12/24-Bit, TTL digital data out), digitally coupled to Analog
Devices AD9754, a 14-bit TxDAC
amplifier configured as a differential driver. See Figure 45 for
schematics of a circuit used to generate DMT signals that can
achieve down to –80 dBc of MTPR performance, sufficient for
use in evaluating xDSL drivers. Note that the DMT waveforms
available with the AD8016ARP-EVAL and AD8016ARB-EVAL
boards or similar WFM files are needed to produce the neces-
sary digital data required to drive the TxDAC from the optional
TTL digital data output of the TEK AWG2021. Copies of these
WFM files can be obtained through the Analog Devices website,
at www.analog.com.
EVALUATION BOARDS
The AD8016ARP-EVAL, AD8016ARB-EVAL, AD8016ARE-
EVAL boards available through Analog Devices provide a platform
for evaluating the AD8016 in an ADSL differential line driver
circuit. The board is laid out to accommodate Analog Devices’
two transformer line driver hybrid circuits (see Figures 46a
and 46b) including line matching network, an RJ11 jack for
interfacing to line simulators, transformer coupled input for
single-to-differential input conversion, and accommodations for
the receiver function. Schematics and layout information are
available for both versions of the evaluation board. Also included
in the package are WFM files for use in generating 14-bit
DMT waveforms. Upstream data is contained in the ...24.wfm
files and downstream data in the ...128.wfm files.
These DMT modulated signals are used to evaluate xDSL
products for multitone power ratio or MTPR performance.
The data files are used in pairs (adslu24.wfm and adsll24.wfm
go together, etc.) and are loaded into a TEK AWG2021 arbi-
trary waveform generator. The adslu24.wfm is loaded via the
TEK AWG2021 floppy drive into Channel 1, while the
adsll24.wfm is simultaneously loaded into Channel 2. The num-
ber in the file name, prefixed with “u,” goes into CH1 or upper
channel and the “l” goes into CH2 or the lower channel. 12 bits
from CH1 are combined with 2 bits from CH2 to achieve 14-bit
digital data at the digital outputs of the TEK AWG2021. The
resulting waveforms produced at the AD9754-EB outputs are then
buffered and amplified by the AD8002 differential driver to achieve
14-bit performance from this DMT signal source.
POWER DISSIPATION
In order to properly size the heat sinking area for the user’s
application, it is important to consider the total power dissipa-
tion of the AD8016. The dc power dissipation for V
(V
For the AD8016 powered on +12 V and –12 V supplies (± V
the number is 0.6 W. In a differential driver circuit (Figure 6),
CC
– V
EE
), or 2 × I
Q
× V
S
.
®
, buffered by an AD8002
AD8016
IN
= 0 is I
S
),
Q