AD9551SLASHPCBZ datasheet(37/40 Pages) AD

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AD9551

Rev. B | Page 37 of 40

REFB Frequency Control (Register 0x26 to Register 0x2D)

Table 30.

Address

Bit

Bit Name

Description

0x26

Enable SPI control of

REFB SDM

Controls REFB frequency division functionality.

0 = REFB frequency division defined by the B[3:0] pins (default).

1 = contents of Register 0x27 to Register 0x2D define REFB frequency division via NB,

MODB, and FRACB.

Bypass REFB SDM

Controls bypassing of the REFB SDM.

0 = allow integer-plus-fractional division (default).

1 = allow integer division only.

Enable REFB SDM

Controls REFB SDM enable and hold functionality.

0 = reset REFB SDM and stop its clocks.

1 = REFB SDM enabled (default).

Enable REFA

Controls REFA enable and power-down functionality.

0 = power down REFA input receiver (ineffective unless Register 0x1A[1] = 1).

1 = normal operation (default).

[3:0]

Unused

Unused.

0x27

[7:0]

FRACB

Bits[19:12] of the 20-bit fractional part of the REFB SDM.

0x28

[7:0]

FRACB

Bits[11:4] of the 20-bit fractional part of the REFB SDM.

0x29

[7:4]

FRACB

Bits[3:0] of the 20-bit fractional part of the REFB SDM.

Default is FRACB = 0100 0000 0000 0000 0000 (262,144).

Note that FRACB assumes twos complement format.

[3:0]

Unused

Unused.

0x2A

[7:2]

6-bit integer divide value for the REFB SDM. Default divide value is 8.

[1:0]

Unused

Unused.

0x2B

Unused

This bit must be programmed to 0, even though the default value is 1.

[6:0]

MODB

Bits[18:12] of the 19-bit modulus of the REFB SDM.

0x2C

[7:0]

MODB

Bits[11:4] of the 19-bit modulus of the REFB SDM.

0x2D

[7:4]

MODB

Bits[3:0] of the 19-bit modulus of the REFB SDM.

Default is MODB = 000 0000 0000 0000 0000.

[3:0]

Unused

Unused.

REFA Delay Control (Register 0x2E and Register 0x2F)

Table 31.

Address

Bit

Bit Name

Description

0x2E

Enable SPI control of REFA

delay

Controls REFA delay functionality.

0 = the device automatically selects REFA delay (default).

1 = REFA delay defined by Register 0x2E[6:0] and Register 0x2F[7:6].

[6:0]

REFA delay control

Bits[8:2] of the 9-bit REFA delay word.

0x2F

[7:6]

REFA delay control

Bits[1:0] of the 9-bit REFA delay word.

Default is 1 0000 0000. Delay granularity is ~150 ps.

[5:0]

Unused

Unused.

REFB Delay Control (Register 0x30 and Register 0x31)

Table 32.

Address

Bit

Bit Name

Description

0x30

Enable SPI control of REFB

delay

Controls REFB delay functionality:

0 = the device automatically selects REFB delay (default).

1 = REFB delay defined by Register 0x30[6:0] and Register 0x31[7:6].

[6:0]

REFB delay control

Bits[8:2] of the 9-bit REFB delay word.

0x31

[7:6]

REFB delay control

Bits[1:0] of the 9-bit REFB delay word.

Default is 1 0000 0000. Delay granularity is ~150 ps.

[5:0]

Unused

Unused.

AD9551/PCBZ Datasheet(PDF) 37 Page - Analog Devices

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