AD8351ARMZ Analog Devices Inc, AD8351ARMZ Datasheet - Page 10

• Manufacturer Part Number: AD8351ARMZ
• Description: IC DIFF AMP RF/IF LOWDIST 10MSOP
• Manufacturer: Analog Devices Inc

Specifications of AD8351ARMZ

• Gain: 26dB
• Rf Type: General Purpose
• Current - Supply: 28mA ~ 32mA
• Frequency: 10MHz ~ 2.5GHz
• P1db: 13.5dBm
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Test Frequency: 10MHz
• Voltage - Supply: 3 V ~ 5 V
• Frequency Range: 2.2GHz
• Power Dissipation Pd: 320mW
• Supply Current: 28mA
• Supply Voltage Range: 3V To 5.5V
• Rf Ic Case Style: MSOP
• No. Of Pins: 10
• Number Of Channels: 1
• Operating Supply Voltage (min): 3V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Package Type: MSOP
• Mounting: Surface Mount
• Pin Count: 10
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Noise Figure: -
• Lead Free Status / Rohs Status: Compliant

AD8351
BASIC CONCEPTS
Differential signaling is used in high performance signal chains,
where distortion performance, signal-to-noise ratio, and low power
consumption is critical. Differential circuits inherently provide
improved common-mode rejection and harmonic distortion perfor-
mance as well as better immunity to interference and ground noise.
Figure 1 illustrates the expected input and output waveforms for
a typical application. Usually the applied input waveform will be
a balanced differential drive, where the signal applied to the INHI
and INLO pins are equal in amplitude and differ in phase by 180°.
In some applications, baluns may be used to transform a single-
ended drive signal to a differential signal. The AD8351 may also be
used to transform a single-ended signal to a differential signal.
GAIN ADJUSTMENT
The differential gain of the AD8351 is set using a single external
resistor, R
can be set to any value between 0 dB and 26 dB using the resistor
values specified in TPC 2, with common gain values provided in
Table I. The board traces used to connect the external gain resis-
tor should be balanced and as short as possible to help prevent
noise pickup and to ensure balanced gain and stability. The low
frequency voltage gain of the AD8351 can be modeled as
where: R
Table I. Gain Resistor Selection for Common Gain Values
(Load Resistance Is Specified as Single-Ended)
Gain, A
0 dB
6 dB
10 dB
20 dB
BALANCED
A
V
SOURCE
=
R
Figure 1. Differential Circuit Representation
G
R
R
V
G
×
F
L
G
, which is connected between Pins 2 and 5. The gain
is 350 Ω (internal).
is the single-ended load resistance.
R
is the gain setting resistor.
L
×
R
4 6 19 5
.
L
R
680 Ω
200 Ω
100 Ω
22 Ω
×
G
+
R
R
(R
G
G
( )
.
L
5 6
1
2
3
4
5
.
= 75
×
PWUP
RGP1
INHI
INLO
RGP2
R
BALANCED
Figure 3. Example of Differential SAW Filter Interface (f
+
G
SOURCE
9 2
+
.
(
)
R
×
L
R
+
F
R
×
R
2 kΩ
470 Ω
200 Ω
43 Ω
R
R
COMM
VOCM
F
VPOS
OPLO
OPHI
R
S
S
G
)
L
×
(R
(
R
R
R
39
10
S
9
8
7
6
T
T
L
= R
= 500
+
T
R
R
0.1 F
0.1 F R
G
L
)
A
A
=
)
V
G
V
OUT
IN
AD8351
2A
VPOS
–10–
COMMON-MODE ADJUSTMENT
The output common-mode voltage level is the dc offset voltage
present at each of the differential outputs. The ac signals are of
equal amplitude with a 180° phase difference but are centered
at the same common-mode voltage level. The common-mode
output voltage level can be adjusted from 1.2 V to 3.8 V by
driving the desired voltage level into the VOCM pin, as illus-
trated in Figure 2.
INPUT AND OUTPUT MATCHING
The AD8351 provides a moderately high differential input
impedance of 5 kΩ. In practical applications, the input of the
AD8351 will be terminated to a lower impedance to provide an
impedance match to the driving source, as depicted in Figure 3.
The terminating resistor, R
the input pins in order to minimize reflections due to imped-
ance mismatch. The 150 Ω output impedance may need to be
transformed to provide the desired output match to a given
load. Matching components can be calculated using a Smith
Chart or by using a resonant approach to determine the match-
ing network that results in a complex conjugate match. The
input and output impedances and reflection coefficients are
provided in TPCs 19, 20, 22, and 23. For additional informa-
tion on reactive matching to differential sources and loads, refer
to the Applications section of the AD8350 data sheet.
Figure 3 illustrates a SAW (surface acoustic wave) filter inter-
face. Many SAW filters are inherently differential, allowing for a
low loss output match. In this example, the SAW filter requires
a 50 Ω source impedance in order to provide the desired center
frequency and Q. The series L shunt C output network provides
a 150 Ω to 50 Ω impedance transformation at the desired frequency
of operation. The impedance transformation is illustrated on a Smith
Chart in Figure 4.
It is possible to drive a single-ended SAW filter simply by con-
necting the unused output to ground using the appropriate
terminating resistance. The overall gain of the system will be
reduced by 6 dB due to the fact that only half of the signal will
be available to the input of the SAW filter.
BALANCED
0.1 F
0.1 F
SOURCE
150
Figure 2. Common-Mode Adjustment
C
8pF
P
27nF
27nF
L
L
S
S
R
G
50
C
1
2
3
4
5
= 190 MHz)
PWUP
RGP1
INHI
INLO
RGP2
190MHz SAW
T
, should be as close as possible to
COMM
VOCM
OPLO
VPOS
OPHI
10
6
9
8
7
R
L
0.1 F
0.1 F
C
DECL
REV. B
V
V
1.2V
TO
3.8V
S
OCM