AD8345ARE-REEL7 Analog Devices Inc, AD8345ARE-REEL7 Datasheet - Page 14

• Manufacturer Part Number: AD8345ARE-REEL7
• Description: IC QUADRATURE MOD 250MHZ 16TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD8345ARE-REEL7

• Rohs Status: RoHS non-compliant
• Function: Modulator
• Lo Frequency: 250MHz ~ 1GHz
• Rf Frequency: 140MHz ~ 1GHz
• P1db: 2.5dBm
• Noise Floor: -155dBm/Hz
• Output Power: 2dBm
• Current - Supply: 78mA
• Voltage - Supply: 2.7 V ~ 5.5 V
• Test Frequency: 800MHz
• Package / Case: 16-TSSOP Exposed Pad, 16-eTSSOP, 16-HTSSOP

AD8345
Note that this circuit assumes that the single-ended I and Q
signals are ground-referenced. Any differential dc-offsets result
in increased LO leakage at the output of the AD8345.
It is possible to drive the baseband inputs with a single-ended
signal biased to 0.7 V, with the unused inputs being biased to a
dc level of 0.7 V. However, this mode of operation is not recom-
mended because any dc level difference between the bias level
of the drive signal and the dc level on the unused input
(including the effect of temperature drift) results in increased
LO leakage. In addition, the maximum output power is reduced
by 6 dB.
RF OUTPUT
The RF output is designed to drive a 50 Ω load but should be ac
coupled as shown in Figure 28. If the I and Q inputs are driven
in quadrature by 1.2 V p-p signals, then the resulting output
power is approximately −1 dBm (see Figure 3). The RF output
impedance is very close to 50 Ω. As a result, no additional
matching circuitry is required if the output is driving a 50 Ω
load.
Q
I
IN
IN
49.9Ω
49.9Ω
24.9Ω
24.9Ω
348Ω
348Ω
1.5kΩ
10kΩ
348Ω
348Ω
0.1μF
0.1μF
348Ω
348Ω
348Ω
348Ω
8
2
1
8
2
1
AD8132
Figure 30. Single-Ended 1Q Drive Circuit
AD8132
+5V
–5V
+5V
–5V
3
6
3
6
0.1μF
5
4
0.1μF
5
4
Rev. B | Page 14 of 20
0.1μF
+
10μF
+
+
10μF
10μF
+
10μF
0.1μF
APPLICATION WITH TxDAC®
Figure 31 shows the AD8345 driven by the AD9761 TxDAC.
(Any of the devices in the Analog Devices’ TxDAC family can
also be used in this application.)
The I and Q DACs generate differential output currents of 0 mA
to 10 mA and 10 mA to 0 mA, respectively. The combination of
140 Ω resistors shunted to ground off each DAC output, along
with 210 Ω resistors shunted between each differential DAC
pair, produces a baseband signal into the AD8345 I and Q
inputs that has a differential peak-to-peak swing of 1.2 V with a
dc common-mode bias of 700 mV.
0.01μF
IBBP
IBBN
QBBP
QBBN
COM1 COM2 COM3
1000pF
SPLITTER
VPS1 VPS2
PHASE
AD8345
Σ
1000pF
VOUT
LOIP
LOIN
0.01μF