ADL5375-05-EVALZ Analog Devices, ADL5375-05-EVALZ Datasheet - Page 26

• Manufacturer Part Number: ADL5375-05-EVALZ
• Description: RF Development Tools ADL5375-05 EVAL
• Manufacturer: Analog Devices
• Type: Modulators / Demodulatorsr
• Series: ADL5375r

Specifications of ADL5375-05-EVALZ

• Rohs: yes
• Product: Evaluation Boards
• Factory Pack Quantity: 1

ADL5375
In CIF applications, a low-pass filter between the DAC and
modulator is still favored to filter out images, noises discussed
in the Filtering section as well as to preserve dc bias level from
DAC to ADL5375-05. Figure 65 shows a fifth order Butterworth
filter with a 300 MHz corner frequency and the frequency
response of this filter is shown in Figure 66.
Even a purely differential filter can work well, splitting the filter
capacitors into two and grounding at filter topology as like C2
and C4 in Figure 65 divert common mode currents to ground
and result in additional common-mode rejection of high
frequency signals to a purely differential filter.
AD9122
Figure 64.
IOUT1N
IOUT2N
IOUT1P
IOUT2
Figure 65. Recommended DAC Modulator Interface Topology with
–1
–2
–3
–4
–5
–6
1
0
1
67
66
59
58
ADL5375-15
RBQN
RBQP
RBIP
RBIN
50Ω
50Ω
50Ω
50Ω
FC = 300 MHz Fifth-Order, Butterworth Filter
3.6pF
3.6pF
BASEBAND FREQUENCY (MHz)
C1Q
C1I
Baseband Frequency Response Normalized to
Response for 1 MHz
10
L1NQ
L1PQ
33nH
33nH
33nH
33nH
L1PI
L1NI
C2NQ
C2PQ
22pF
22pF
22pF
22pF
C2PI
C2NI
L2NQ
L2PQ
33nH
33nH
33nH
33nH
L2NI
L2PI
C3Q
6pF
6pF
C3I
100
C4PI
3pF
C4NI
3pF
C4NQ
3pF
C4PQ
3pF
RSLQ
100Ω
100Ω
RSLI
21
22
10
9
ADL5375-05
IBBP
IBBN
QBBN
QBBP
1k
Rev. B | Page 26 of 36
Driving the ADL5375-15 with a TXDAC
The
requires a slightly more complex interface that performs a dc
level shift on the baseband signals. It is necessary to level-shift
the DAC output from a 500 mV dc bias to the 1500 mV dc bias
that the
Level-shifting can be achieved with either a passive network
or an active circuit. A passive network of resistors is shown
in Figure 67. In this network, the dc bias of the DAC remains at
500 mV while the input to the
be noted that this passive level-shifting network introduces
approximately 2 dB of loss in the ac signal.
The active level shifting circuit involves the use of the
dual-differential amplifier. This device has a VOCM pin that
sets the output dc bias. Through this pin, the output common-
mode of the amplifier can be easily set to the requisite 1.5 V for
biasing the
AD9122
Figure 66. Frequency Response for DAC Modulator Interface with 300 MHz
–10
–15
–20
–25
IOUT1P
IOUT1N
IOUT2N
–5
ADL5375-15
Figure 67. Passive Level-Shifting Network For Biasing
0
IOUT2
1M
ADL5375-15
ADL5375-15
67
66
59
58
RBQN
RBQP
45.3Ω
45.3Ω
45.3Ω
45.3Ω
RBIP
RBIN
requires a 1500 mV dc bias and therefore
Fifth-Order Butterworth Filter
requires.
10M
FREQUENCY (Hz)
baseband inputs.
RSQN
RSQP
RSIN
RSIP
from TxDAC
1kΩ
1kΩ
1kΩ
1kΩ
ADL5375-15
3480Ω
3480Ω
3480Ω
3480Ω
RLQN
RLQP
RLIN
RLIP
100M
5V
5V
is 1500 mV. It should
21
22
10
9
Data Sheet
ADL5375-15
ADL5375-15
IBBP
IBBN
QBBN
QBBP
500M
ADA4938
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0