AD9154 datasheet(29/124 Pages) AD

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Data Sheet

AD9154

Rev. C | Page 29 of 124

INTERPOLATION

The transmit path can use zero to three cascaded interpolation

filters, which each provide a 2× increase in output data rate and

a low-pass function. Table 25 shows the different interpolation

modes and the respective usable bandwidth, along with the

maximum fDATA rate attainable.

Table 25. Interpolation Modes and Their Usable Bandwidth

Interpolation Mode

InterpMode

Usable Bandwidth

1× (bypass)

0x00

0.5× fDATA

2×

0x01

0.4 × fDATA

4×

0x03

0.4 × fDATA

8×

0x04

0.4 × fDATA

The usable bandwidth is defined for 1×, 2×, 4×, and 8× modes

as the frequency band over which the filters have a pass-band

ripple of less than ±0.001 dB and an image rejection of greater

than 85 dB. For more information, see the Interpolation section.

JESD204B SETUP

This section explains how to select a JESD204B operating mode

for a desired application. This in turn defines appropriate values

for CheckSumMode, UnusedLanes, DualLink, CurrentLink,

Scrambling, L, F, K, M, N, Np, Subclass, S, HD, Lane0Checksum,

and Lanes needed for the Step 3: Transport Layer section.

Note that DualLink, Scrambling, L, F, K, M, N, Np, S, HD, and

Subclass must have the same settings on the transmit side.

For a summary of how a JESD204B system works and what

each parameter means, see the JESD204B Serial Data Interface

section.

Available Operating Modes

Table 26. JESD204B Operating Modes (Single Link Only)

Mode

Parameter

M (Converter Count)

L (Lane Count)

S ((Samples per Converter) per Frame)

F ((Octets per Frame) per Lane)

Table 27. JESD204B Operating Modes (Single or Dual Link)

Mode

Parameter

M (Converter Count)

L (Lane Count)

S ((Samples per Converter) per Frame)

F ((Octets per Frame) per Lane)

For a particular application, the number of converters to use

(M) and the fDATA (DataRate) are known. The LaneRate and

number of lanes (L) can be traded off as follows:

DataRate = (DACRate)/(InterpolationFactor)

LaneRate = (20 × DataRate × M)/L

where LaneRate is specified in Table 4.

Octets per frame per lane (F) and samples per convertor per

frame (S) define how the data is packed. If F = 1, the high density

(HD) setting must be set to 1 (HD = 1). Otherwise, set HD = 0.

Both the converter resolution (N) and the bits per sample (Np)

must be set to 16. K must be set to 32 for Mode 0, Mode 4 and

Mode 9. Other modes may use either K = 16 or K = 32.

DualLink

DualLink sets up two independent JESD204B links; each link

can be reset independently. If DualLink is desired, set it to 1; if a

single link is desired, set DualLink to 0. Note that Link 0 and

Link 1 must have identical parameters. The operating modes

available when using dual link mode are shown in Table 26. In

addition to these operating modes, the modes in Table 27 may

also be used when using single link mode.

Scrambling

Scrambling is a feature that makes the spectrum of the link data

independent. This avoids spectral peaking and provides some

protection against data dependent errors caused by frequency

selective effects in the electrical interface. Set Scrambling to 1 if

scrambling is being used, or to 0 if it is not.

Subclass

Subclass determines whether the latency of the device is

deterministic, meaning it requires an external synchronization

signal. See the Subclass Setup section for more information.

CurrentLink

To configure Link 0 or Link 1, set CurrentLink to either 0 or 1,

respectively.

Lanes

Lanes enables and deskews particular lanes in two thermometer

coded registers.

Lanes = (2L) − 1

UnusedLanes

UnusedLanes turns off unused circuit blocks to save power.

Each physical lane not being used (SERDINx±) must be

powered off by writing a 1 to the corresponding bit of

For example, if using Mode 6 in dual link mode and sending

data on SERDIN0±, SERDIN1±, SERDIN4±, and SERDIN5±,

set UnusedLanes = 0xCC to power off Physical Lane 2, Physical

Lane 3, Physical Lane 6, and Physical Lane 7.

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