ADL5246ACPZN-R7 datasheet(24/36 Pages) AD

24 / 36 page

ADL5246

Data Sheet

Rev. A | Page 24 of 36

Amplifier 3 (AMP3)

AMP3 is a broadband 1⁄2 watt driver requiring band specific

matching to achieve the specified performance. The input and

output are easily matched using a combination of series and

shunt capacitors and a microstrip line serving as an inductor.

VPOS2 provides dc bias to the internal bias circuit. Bias for the

output stage is supplied to the amplifier via the L4 inductor that

is connected to RFOUT3. Therefore, both VPOS2 and VCC2 must

be connected to bias to operate AMP3. Capacitors C24, C25, and

C26 provide the power supply decoupling. When AMP3 is not in

use, terminate the RFIN3 and RFOUT3 pins to ground via a 100 pF

capacitor and a 50 Ω resistor in series on each pin. Figure 78

shows the matching components for operation at 2.2 GHz.

Gain Control

The integrated VVAs are controlled by VGAIN1 and VGAIN2.

The attenuators maybe controlled independently, if desired. The

gain control voltage range is 0 V to 3.3 V. R4 and R5 isolate the

gain control circuit from external capacitance. Capacitors C14

and C15 provide decoupling.

VSW1 and VSW1 are complementary 3 V logic that is used to

control the bypass switch operation and are detailed in Table 5.

R2 and R3 isolate the logic control circuitry from external

capacitance. The C6 and C11 capacitors provide decoupling.

Figure 9 through Figure 14 show that operating AMP2 at 5 V

gives greater gain range; however, operating at 3.3 V gives better

phase linearity. Operating at 5 V gives better temperature stability,

as shown in Figure 17. It is possible to operate the gain control

section at 5 V while operating the remainder of the ADL5246 at

3.3 V for reduced power consumption.

Amplifier 3 Matching

The input and output of the driver amplifier, AMP3, can be

matched to 50 Ω using two to three external components. The

microstrip transmission line is used as an inductor. The matching

component values are listed in Table 6. All capacitors are

Murata GRM15 series (0402 size), L4 is a Coilcraft® 0603CS

series (0603 size). The 0603 size is preferred over the 0402 size

for additional current handling capability. The self resonance of

L4 has little bearing on the performance of AMP3, within

reasonable limits. For all frequency bands, the placement of C1,

C3, and L6 are critical. Table 7 lists the component spacing for

C1, C3, and L6. The placement of C3 and R1 are fixed for the

matching network on the evaluation board. The spacing is 69 mils

and 301 mils, respectively. In the case of 0.75 GHz and 0.9 GHz,

a 2 Ω resistor is used in place of the capacitor in the C21 location.

Table 6. Matching Component Values on the ADL5246 Evaluation Board

Frequency (GHz)

C21

C3 (pF)

L6 (nH)

C1 (pF)

C23 (pF)

R1 (Ω)

0.75

2 Ω

3.3

8.2

100

0.9

2 Ω

3.3

100

1.9

100 pF

2.7

100

2.2

100 pF

1.5

2.7

100

2.6

100 pF

1.0

2.2 F

100

Table 7. Matching Component Spacing on the ADL5246 Evaluation Board

Frequency (GHz)

C3: λ1 (mils)

L6: λ2 (mils)

R1 (mils)

C1: λ3 (mils)

0.75

301

528.4

0.9

301

422.4

1.9

301

184.2

2.2

301

75.4

2.6

301

75.4

ADL5246ACPZN-R7 Arkusz danych(PDF) 24 Page - Analog Devices

ADL5246ACPZN-R7 Arkusz danych(HTML) 24 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 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Arkusz danych Pobierz

Link URL