AD8314

Rev. B | Page 18 of 20

OPERATION AT 2.7 GHz

While the AD8314 is specified to operate at frequencies up to

2.5 GHz, it works at higher frequencies, although it does exhibit

slightly higher output voltage temperature drift. Figure 43

shows the transfer function of a typical device at 2.7 GHz, at

ambient as well as hot and cold temperatures.

Figure 44 shows the transfer function of the AD8314 when

driven by both an unmodulated sine wave and a 64 QAM

signal. As previously discussed, the higher peak-to-average ratio

of the 64 QAM signal causes an increase in the intercept.

In this case, the intercept increases by approximately 1.5 dB,

causing the overall transfer function to drop by the same

amount. For precision operation, the AD8314 should be

calibrated for each signal type that is driving it.

USING THE LFCSP PACKAGE

On the underside of the LFCSP package, there is an exposed,

compressed paddle. This paddle is internally connected to the

chip’s ground. While the paddle can be connected to the printed

circuit board’s ground plane, there is no thermal or electrical

requirement to do this.

EVALUATION BOARD

Figure 45 shows the schematic of the AD8314 MSOP

evaluation board. The layout and silkscreen of the component

side are shown in Figure 46 and Figure 47. An evaluation board

is also available for the LFCSP package. (For exact part numbers,

see the Ordering Guide.) Apart from the slightly smaller device

footprint, the LFCSP evaluation board is identical to the MSOP

board. The board is powered by a single supply in the 2.7 V to

5.5 V range. The power supply is decoupled by a single 0.1 μF

capacitor. Additional decoupling, in the form of a series resistor

or inductor in R9, can also be added. Table 7 details the various

configuration options of the evaluation board.

1.2

0

–70

10

INPUT POWER (dBm)

3

–3

–2

–1

0

1

2

1.0

0.8

0.6

0.4

0.2

+25°C

–40°C

–40°C

+25°C

+80°C

+80°C

–60

–50

–40

–30

–20

–10

0

Figure 43. Operating at 2.7 GHz

1.2

0

–70

10

INPUT POWER (dBm)

3

–3

–2

–1

0

1

2

1.0

0.8

0.6

0.4

0.2

–60

–50

–40

–30

–20

–10

0

CW

CW

64 QAM

64 QAM

Figure 44. Shift in Transfer Function due to 64 QAM

VSET

LK1

INPUT

SW1

V_DN

V_UP

VPOS

C1

0.1µF

1

2

3

4

ENBL

RFIN

AD8314

8

7

6

5

VSET

FLTR

V_DN

VPOS

COMM

V_UP

R2

52.3Ω

R1

0Ω

R7

0Ω

R8

OPEN

C4

(OPEN)

R4

(OPEN)

C2

(OPEN)

R6

(OPEN)

C3

(OPEN)

R3

0Ω

R5

0Ω

R9

0Ω

Figure 45. Evaluation Board Schematic