AD6684 datasheet(59/107 Pages) AD

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Data Sheet

AD6684

Rev. 0 | Page 59 of 107

JESD204B Tx CONVERTER MAPPING

To support the different chip operating modes, the AD6684

design treats each sample stream (real or I/Q) as originating

from separate virtual converters. The I/Q samples are always

mapped in pairs with the I samples mapped to the first virtual

converter and the Q samples mapped to the second virtual

converter. With this transport layer mapping, the number of

virtual converters are the same whether



A single real converter is used along with a digital

downconverter block producing I/Q outputs, or



An analog downconversion is used with two real

converters producing I/Q outputs.

Figure 97 shows a block diagram of the two scenarios described

for I/Q transport layer mapping.

The JESD204B Tx block for AD6684 supports up to four DDC

blocks. Each DDC block outputs either two sample streams

(I/Q) for the complex data components (real + imaginary), or

one sample stream for real (I) data. The JESD204B interface can

be configured to use up to eight virtual converters depending on

the DDC configuration. Figure 98 shows the virtual converters

and their relationship to the DDC outputs when complex outputs

are used. Table 33 shows the virtual converter mapping for each

chip operating mode when channel swapping is disabled.

REAL

CONVERTER 0

CONVERTER 1

ADC

90°

PHASE

JESD204B

L LANES

I/Q ANALOG MIXING

M = 2

ADC

REAL

CONVERTER 0

CONVERTER 1

JESD204B

L LANES

DIGITAL DOWNCONVERSION

M = 2

DIGITAL

DOWNCONVERSION

Figure 97. I/Q Transport Layer Mapping

DDC 0

REAL/I

CONVERTER 0

CONVERTER 1

REAL/I

REAL/Q

DDC 1

REAL/I

CONVERTER 2

CONVERTER 3

REAL/I

REAL/Q

DDC 0

REAL/I

CONVERTER 4

CONVERTER 5

REAL/I

REAL/Q

DDC 1

REAL/I

CONVERTER 6

CONVERTER 7

REAL/I

REAL/Q

I/Q

CROSSBAR

MUX

I/Q

CROSSBAR

MUX

OUTPUT

INTERFACE

OUTPUT

INTERFACE

ADC

SAMPLING

REAL/I

ADC

SAMPLING

REAL/Q

ADC A

SAMPLING

REAL/I

ADC

SAMPLING

REAL/Q

Figure 98. DDCs and Virtual Converter Mapping

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