AD8348ARUZ-REEL7 Analog Devices Inc, AD8348ARUZ-REEL7 Datasheet - Page 21

• Manufacturer Part Number: AD8348ARUZ-REEL7
• Description: IC,Quadrature Demodulator,BIPOLAR,TSSOP,28PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of AD8348ARUZ-REEL7

• Function: Demodulator
• Lo Frequency: 100MHz ~ 2GHz
• Rf Frequency: 50MHz ~ 1GHz
• P1db: -22dBm
• Gain: 25.5dB
• Noise Figure: 10.75dB
• Current - Supply: 58mA
• Voltage - Supply: 2.7 V ~ 5.5 V
• Package / Case: 28-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

If the MX inputs are to be driven from a single-ended 50 Ω source,
a 4:1 balun can be used to transform the 200 Ω impedance of
the inputs to 50 Ω while performing the required single-ended-
to-differential conversion. The recommended transformer is the
M/A-COM ETK4-2T.
BASEBAND OUTPUTS
The baseband amplifier outputs, IOPP, IOPN, QOPP, and QOPN,
should be presented with loads of at least 2 kΩ (single-ended to
ground). They are not designed to drive 50 Ω loads directly. The
typical swing for these outputs is 2 V p-p differential (1 V p-p
single-ended), but larger swings are possible as long as care is taken
to ensure that the signals remain within the lower limit of 0.5 V
and the upper limit of V
a larger swing, it is necessary to adjust the common-mode bias of
the baseband output signals. Increasing the swing can have the
benefit of improving the signal-to-noise ratio of the baseband
amplifier output.
When connecting the baseband outputs to other devices, care
should be taken to ensure that the outputs are not capacitively
loaded by approximately 20 pF or more. Such loads could
potentially overload the output or induce oscillations. The effect
of capacitive loading on the baseband amplifier outputs can be
mitigated by inserting series resistors of approximately 200 Ω.
OUTPUT DC BIAS LEVEL
The dc bias of the mixer outputs and the baseband amplifier
inputs and outputs is determined by the voltage that is driven
onto the VCMO pin. The range of this voltage is typically
between 500 mV and 4 V when operating with a 5 V supply.
To achieve maximum voltage swing from the baseband amplifiers,
VCMO should be driven at 2.25 V; this allows a swing of up to
7 V p-p differential (3.5 V p-p single-ended).
INTERFACING TO DETECTOR FOR AGC OPERATION
The AD8348 can be interfaced with a detector such as the
AD8362 rms-to-dc converter to provide an automatic signal-
leveling function for the baseband outputs.
MXIN
MXIP
Figure 54. Driving the MX Inputs from a Single-Ended 50 Ω Source
Figure 53. Driving the MX Inputs from a Differential Source
19
18
MXIN
MXIP
1µF
19
18
S
− 1 V of the output swing. To achieve
1000pF
1000pF
ETK4-2T
1000pF
1000pF
MXIN
MXIP
MXIP
Rev. A | Page 21 of 28
Z
Assuming the I and Q channels have the same rms power, the
mixer output (or the output of the baseband filter) of one channel
can be used as the input of the AD8362. The AD8362 should be
operated in a region where its linearity error is small. Also, a
voltage divider should be implemented with an external resistor
in series with the 200 Ω input impedance of the AD8362 input.
This attenuates the AD8348 mixer output so that the AD8362
input is not overdriven. The size of the resistor between the
mixer output and the AD8362 input should be chosen so that
the peak signal level at the input of the AD8362 is about 10 dB
less than the approximately 10 dBm maximum of the AD8362
dynamic range.
The other side of the AD8348 baseband output should be
loaded with a resistance equal to the series resistance of the
attenuating resistor in series with the AD8362’s 200 Ω input
impedance. This resistor should be tied to the source driving
VCMO so that there is no dc drawn from the mixer output.
IF INPUT
O
= 200Ω
+V
S
TO BASEBAND
+V
S
I ADC
0.1µF
1.02kΩ
Figure 55. AD8362 Configuration for AGC Operation
V
REF
0.1µF
100pF
1000pF
100pF
100pF
V
REF
1000pF
1000pF
1µF
1µF
1µF
1µF
1000pF
LO
10
11
12
13
14
1
2
3
4
5
6
7
8
9
1
2
3
4
5
6
7
8
LOIP
VPOS1 COM1
IOPN
IOPP
VCMO
IAIN
COM3
IMXO
COM2 VPOS3
IFIN
IFIP
VPOS2
IOFS
VREF
COMM
CHPF
DECL
INHI
INLO
DECL
PWDN
COMM
AD8348
AD8362
60.4Ω
4
3
5
1
QMXO
ACOM
ACOM
QOPN
QOPP
ENVG
COM3
QOFS
ENBL
VPOS
VOUT
VREF
VTGT
VSET
CLPF
QAIN
MXIN
MXIP
VGIN
LOIN
1:1
1000pF
28
27
26
25
24
23
22
21
20
19
18
17
16
15
16
15
14
13
12
11
10
9
1000pF
1000pF
1µF
+V
100pF
S
100pF
100pF
100pF
V
SET
0.1µF
+V
0.1µF
1.24kΩ
TO BASEBAND
AD8348
S
Q ADC
+V
S
+V
V
CMO
S