ADL5566ACPZ-R7 datasheet(18/24 Pages) AD

18 / 24 page

ADL5566

Data Sheet

Rev. C | Page 18 of 24

ADC INTERFACING

The ADL5566 is a dual high output linearity amplifier that is

optimized for ADC interfacing. One option of applying the

ADL5566 to drive an ADC is shown in Figure 47. The wideband

1:1 transmission line balun provides a differential input to the

amplifier, and the 36 Ω resistors provide a 50 Ω match to the

source. The ADL5566 is ac-coupled from the input and output

to avoid common-mode loading. A reference voltage is

required to bias the AD9268 inputs and is delivered through

the 200 Ω resistors. These, in parallel with the 400 Ω resistor,

create the low frequency amplifier load of 200 Ω. The 56 nH

inductors and the 56 pF capacitor are used to create a 70 MHz

low-pass filter. The two 25 Ω resistors are added to raise the

ADL5566 output impedance, which reduces peaking when the

filter drives a light load. The two 25 Ω resistors provide isolation to

the switching currents of the ADC sample-and-hold circuitry.

The AD9268 dual ADC presents a 6 kΩ differential load

impedance and requires a 1 V p-p to 2 V p-p input signal to

reach full scale. The system frequency response is shown in

Figure 46. By applying a 2 V p-p, 32 MHz single-tone signal from

the ADL5566 in a gain of 16 dB, an SFDR of 94.6 dBc is achieved.

By applying two half scale signals of 32 MHz and 33 MHz from

the ADL5566 in a gain of 16 dB, an SFDR of 90.5 dBc is

realized.

24303642

5460

FREQUENCY (MHz)

–15

–30

–45

–60

–75

–90

–105

–120

–135

–150

SNR = 74.28dB

FUND FREQ = 32.123MHz

FUND POWER = –1.014dBFS

SECOND HARM = –94.629dBc

THIRD HARM = –95.19dBc

FOURTH HARM = –99.98dBc

FIFTH HARM = –104.971dBc

SIXTH HARM = –107.105dBc

Figure 44. Measured Single-Tone Performance of the Circuit in Figure 47 for a

32 MHz Input Signal

FREQUENCY (MHz)

–15

–30

–45

–60

–75

–90

–105

–120

–135

–150

FUNDAMENTAL1 = –7.03dBFS

FUNDAMENTAL2 = –7.05dBFS

IMD (2f1 – f2) = –90.53dBc

IMD (2f2 + f1) = –96.81dBc

NOISE FLOOR = –114.703dB

Figure 45. Measured Two-Tone Performance of the Circuit in Figure 47 for a

32 MHz and 33 MHz Input Signals

–20

–19

–18

–17

–16

–15

–14

–13

–12

–11

–10

–9

–8

–7

–6

–5

–4

–3

–2

–1

100

120

140

160

FREQUENCY (MHz)

Figure 46. Measured Relative Frequency Response of the Wideband ADC

Interface Depicted in Figure 47

VIN_1

VIP_1

56pF

AD9268

SIDE A

ETC1-1

VCC

200Ω

0.1µF

–

ADL5566

0.1µF

50Ω

36Ω

400Ω

25Ω

VREF

25Ω

Figure 47. Wideband ADC Interfacing Example Featuring the AD9268

ADL5566ACPZ-R7 Datasheet(PDF) 18 Page - Analog Devices

ADL5566ACPZ-R7 Datasheet(HTML) 18 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

Datasheet Download

Link URL