AD8347 datasheet(14/20 Pages) AD

14 / 20 page

REV. 0

AD8347

–14–

less than 400

µA of supply current. The reference voltage (VREF)

of 1.0 V, which serves as the common-mode reference for the

baseband circuits, is made available for external use.

OPERATING THE AD8347

Basic Connections

Figure 4 shows the basic connections for operating the AD8347.

The device is powered through three power supply pins: VPS1,

VPS2, and VPS3. These pins supply current to different parts of

the overall circuit. VPS1 and VPS2 power the Local Oscillator (LO)

and RF sections, respectively, while VPS3 powers the baseband

amplifiers. While all of these pins should be connected to the same

supply voltage, each pin should be separately decoupled using two

capacitors. 100 pF and 0.1

µF are recommended (values close

to these may also be used).

A supply voltage in the range 2.7 V to 5.5 V should be used. The

quiescent current is 64 mA when operating from a 5 V supply.

By pulling the ENBL pin low, the device goes into its power- down

mode. The power-down current is 400

µA when operating on a

5 V supply and 80

µA on a 2.7 V supply.

Like the supply pins, the individual sections of the circuit are

separately grounded. COM1, COM2, and COM3 provide ground

for the LO, RF, and baseband sections respectively. All of these

pins should be connected to the same low impedance ground.

RF Input and Matching

The RF input signal should be ac-coupled into the RFIP pin and

RFIN should be ac-coupled to ground. To improve broadband

matching to a 50

Ω source, a 200 Ω resistor may be connected

from the signal side of RFIP’s coupling capacitor to ground.

LO Drive Interface

For optimum performance the LO inputs, LOIN and LOIP,

should be driven differentially. M/A-COM balun, ETC1-1-13

is recommended. Unless an (ac-coupled) transformer is being

used to generate the differential LO, the inputs must be ac-coupled

as shown. To improve broadband matching to a 50

Ω source, a

200

Ω shunt resistor may be connected between LOIP and LOIN.

An LO drive level of –8 dBm is recommended. TPC 17a shows

the relationship between LO drive level, LO frequency, and

quadrature error for a typical device.

A single-ended drive is also possible as shown in Figure 5, but

this will slightly increase LO leakage. The LO signal should be

applied through a coupling capacitor to LOIP, and LOIN should

be ac-coupled to ground. Because the inputs are fully differen-

tial, the drive orientation can be reversed. As in the case of the

differential drive, a 200

Ω resistor connected across LOIP and

LOIN improves the match to a 50

Ω source.

RFIN

VREF

RFIP

VPS2

IMXO

COM3

IOPP

IOFS

IOPN

VCMO

VPS1

LOIN

IAIN

COM2

QOPN

COM3

VGIN

ENBL

LOIP

COM1

VPS3

AD8347

PHASE

SPLITTER

BIAS

CELL

DET 1

VREF

GAIN

CONTROL

INTERFACE

DET 2

VREF

VCMO

PHASE

SPLITTER

VCMO

VDT2

QMXO

QOPP

QOFS

VAGC

VDT1

QAIN

760mV p-p

DIFFERENTIAL

(AGC MODE)

VCM = 1V

QOPP

QOPN

LO INPUT

–8dBm

0.8GHz–2.7GHz

ETC 1-1-13

(M/A-COM)

100pF

R17

200

100pF

760mV p-p

DIFFERENTIAL

(AGC MODE)

VCM = 1V

C10

100pF

0.1 F

100pF

0.1 F

100pF

+VS

(2.7V–5.5V)

RF INPUT

0.8GHz–2.7GHz

0dBm MAX

(AGC MODE)

100pF

200

C14

0.1 F

24mV p-p

(AGC MODE)

1V BIAS (VREF)

24mV p-p

(AGC MODE)

1V BIAS (VREF)

C13

0.1 F

IOPP

IOPN

C15

0.1 F

Figure 4. Basic Connections

AD8347 Datasheet(PDF) 14 Page - Analog Devices

AD8347 Datasheet(HTML) 14 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Datasheet Download

Link URL