adl5382 Analog Devices, Inc., adl5382 Datasheet - Page 15

• Manufacturer Part Number: adl5382
• Description: 700 Mhz To 2.7 Ghz Quadrature Demodulator
• Manufacturer: Analog Devices, Inc.

RF INPUT
The RF inputs have a differential input impedance of
approximately 50 Ω. For optimum performance, the RF port
should be driven differentially through a balun. The recommended
balun is the M/A-COM ETC1-1-13. The RF inputs to the device
should be ac-coupled with 1000 pF capacitors. Ground-referenced
choke inductors must also be connected to RFIP and RFIN (the
recommended value is 33 nH, Coilcraft 0603CS-33NX) for
appropriate biasing. Several important aspects must be taken
into account when selecting an appropriate choke inductor for
this application. First, the inductor must be able to handle the
approximately 40 mA of standing dc current being delivered
from each of the RF input pins (RFIP, RFIN). The suggested
0603 inductor has a 600 mA current rating. The purpose of the
choke inductors is to provide a very low resistance dc path to
ground and high ac impedance at the RF frequency so as not to
affect the RF input impedance. A choke inductor that has a self-
resonant frequency greater than the RF input frequency ensures
that the choke is still looking inductive and therefore has a more
predictable ac impedance (jωL) at the RF frequency. Figure 42
shows the RF input configuration.
RF INPUT
ETC1-1-13
Figure 42. RF Input
33nH
33nH
1000pF
1000pF
21
22
RFIN
RFIP
Rev. 0 | Page 15 of 28
The differential RF port return loss is characterized as shown in
Figure 43.
BASEBAND OUTPUTS
The baseband outputs QHI, QLO, IHI, and ILO are fixed
impedance ports. Each baseband pair has a 50 Ω differential
output impedance. The outputs can be presented with differential
loads as low as 200 Ω (with some degradation in gain) or high
impedance differential loads (500 Ω or greater impedance yields
the same excellent linearity) that is typical of an ADC. The
TCM9-1 9:1 balun converts the differential IF output to single-
ended. When loaded with 50 Ω, this balun presents a 450 Ω
load to the device. The typical maximum linear voltage swing
for these outputs is 2 V p-p differential. The bias level on these
pins is equal to VPOS − 2.8 V. The output 3 dB bandwidth is
370 MHz. Figure 44 shows the baseband output configuration.
–10
–12
–14
–16
–18
–20
–22
–24
0.7
0.9
Figure 44. Baseband Output Configuration
Figure 43. Differential RF Port Return Loss
QLO
1.1
QHI
ILO
IHI
1.3
16
15
14
13
1.5
FREQUENCY (GHz)
1.7
1.9
2.1
QHI
QLO
IHI
ILO
2.3
2.5
ADL5382
2.7
2.9