AD8351ARMZ Analog Devices Inc, AD8351ARMZ Datasheet - Page 11

• 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

SINGLE-ENDED-TO-DIFFERENTIAL OPERATION
The AD8351 can easily be configured as a single-ended-to-
differential gain block, as illustrated in Figure 5. The input signal
is ac-coupled and applied to the INHI input. The unused input is
ac-coupled to ground. The values of C1 through C4 should be
selected such that their reactances are negligible at the desired
frequency of operation. To balance the outputs, an external feed-
back resistor, R
feedback resistor, refer to Figures 6a and 6b. From Figure 6a,
select an R
from Figure 6b an R
Even though the differential balance is not perfect under these
conditions, the distortion performance is still impressive. TPCs 10
and 11 show the second and third harmonic distortion perfor-
mance when driving the input of the AD8351 using a single-ended
50 Ω source.
REV. B
Figure 4. Smith Chart Representation of SAW
Filter Output Matching Network
10
35
30
25
20
15
10
5
0
G
0
for the required dB gain at a given load. Next, select
Figure 5. Single-Ended Application
R
25
50
F
L
, is required. To select the gain resistor and the
= 150
Figure 6a. Gain Selection
R
50
F
L
resistor for the selected R
= 1000
0.1 F
0.1 F
25
R
SERIES L
G
50
50
AD8351
R
100
G
( )
10
R
L
R
25
F
= 500
150
50
0.1 F
0.1 F
SHUNT C
100
100
G
and load.
R
200
L
500
200
500
0
1000
–11–
ADC DRIVING
The circuit in Figure 7 represents a simplified front end of the
AD8351 driving the AD6645, which is a 14-bit, 105 MSPS A/D
converter. For optimum performance, the AD6645 and the
AD8351 are driven differentially. The resistors R1 and R2 present
a 50 Ω differential input impedance to the source with R3 and R4
providing isolation from the A/D input. The gain setting resistor
for the AD8351 is R
load to the AD8351 and requires a 2.2 V p-p differential signal
between AIN and AIN for a full-scale output. This AD8351
circuit then provides the gain, isolation, and source matching for
the AD6645. The AD8351 also provides a balanced input, not
provided by the balun, to the AD6645, which is essential for
second-order cancellation. The signal generator is bipolar,
centered around ground. Connecting the VOCM pin (10) of the
AD8351 to the VREF pin of the AD6645 sets the common-mode
output voltage of the AD8351 at 2.4 V. This voltage is bypassed
with a 0.1 µF capacitor. Increasing the gain of the AD8351 will
increase the system noise and thus decrease the SNR but will
not significantly affect the distortion. The circuit in Figure 7 can
provide SFDR performance of better than –90 dBc with a 10 MHz
input and –80 dBc with a 70 MHz input at a gain of 10 dB.
The circuit of Figure 8 represents a single-ended input to differ-
ential output configuration of the AD8351 driving the AD6645.
In this case, R1 provides the input impedance. R
setting resistor. The resistor R
voltages required for second-order cancellation by the AD6645
and can be selected using a chart. (See the Single-Ended-to-
Differential Operation section.) The circuit depicted in Figure 8
can provide SFDR performance of better than –90 dBc with a
10 MHz input and –77 dBc with a 70 MHz input.
Figure 7. ADC Driving Application Using Differential Input
BALANCE
SOURCE
50
7
6
5
4
3
2
1
0
0
Figure 6b. Feedback Resistor Selection
R
L
25
25
= 150
100nF
100nF
R
G
L
. The AD6645 presents a 1 kΩ differential
R
INLO
= 1000
G
INHI
R
L
AD8351
= 500
F
R
is required to balance the output
VOCM
100
OPHI
G
( )
OPLO
25
25
AD8351
AIN
AIN VREF
AD6645
G
is the gain
1000
DIGITAL
OUT