AD9684 View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

AD9684

14-Bit, 500 MSPS LVDS, Dual Analog-to-Digital Converter

Analog Devices 

Product

Overview

Data Sheet

Online

Documentation

Design

Resources

Discussion

ADC

REAL INPUT—SAMPLED AT fS

REAL

BANDWIDTH OF

INTEREST IMAGE

ADC

SAMPLING

REAL

AT fS

BANDWIDTH OF

INTEREST

Sample

& Buy

AD9684

–fS/2

–fS/32 fS/32

–fS/3

–fS/4

–fS/8 –fS/16 DC

fS/16 fS/8

fS/4

FREQUENCY TRANSLATION STAGE (OPTIONAL)

DIGITAL MIXER + NCO FOR fS/3 TUNING, THE FREQUENCY

TUNING WORD = ROUND ((fS/3)/fS × 4096) = +1365 (0x555)

REAL

12-BIT

NCO

I

cos(wt)

90°

0°

–sin(wt)

Q

DIGITAL FILTER

RESPONSE

BANDWIDTH OF INTEREST

(–6dB LOSS DUE TO

NCO + MIXER)

fS/3

fS/2

NCO TUNES CENTER OF

BANDWIDTH OF INTEREST

TO BASEBAND

BANDWIDTH OF

INTEREST IMAGE

(–6dB LOSS DUE TO

NCO + MIXER)

–fS/32 fS/32

–fS/2

–fS/3

–fS/4

–fS/8 –fS/16

DC

fS/16 fS/8

fS/4

fS/3

fS/2

FILTERING STAGE

4 DIGITAL HALF-BAND FILTERS

(HB4 + HB3 + HB2 + HB1)

HB4 FIR

HALF-

I

BAND

FILTER

2

HB3 FIR

HALF-

BAND

FILTER 2

HB2 FIR

HALF-

BAND

FILTER 2

HB1 FIR

HALF-

BAND

FILTER

I

HB4 FIR

HALF-

Q

BAND

FILTER

2

HB3 FIR

HALF-

BAND

FILTER 2

DIGITAL FILTER

RESPONSE

HB2 FIR

HALF-

BAND

FILTER 2

HB1 FIR

HALF-

BAND

FILTER

Q

6dB GAIN TO

COMPENSATE FOR

NCO + MIXER LOSS

GAIN STAGE (OPTIONAL)

0dB OR 6dB GAIN

I

2

I

+6dB

COMPLEX (I/Q) OUTPUTS

DECIMATE BY 16

GAIN STAGE (OPTIONAL)

0dB OR 6dB GAIN

COMPLEX TO REAL

CONVERSION STAGE (OPTIONAL)

fS/4 MIXING + COMPLEX FILTER TO REMOVE Q

REAL (I) OUTPUTS

DECIMATE BY 8

–fS/32 fS/32

–fS/8 –fS/16

DC

fS/16 fS/8

I

I

+6dB

Q

Q

+6dB

COMPLEX REAL/I

TO

REAL

Q

2

Q

+6dB

–fS/32

–fS/16

DC

fS/32

fS/16

DOWNSAMPLE BY 2

6dB GAIN TO

COMPENSATE FOR

NCO + MIXER LOSS

–fS/32 fS/32

–fS/8 –fS/16

DC

fS/16 fS/8

Figure 59. DDC Theory of Operation Example (Real Input, Decimate by 16)

Rev. 0 | Page 33 of 64

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