AD9551SLASHPCBZ datasheet(33/40 Pages) AD

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AD9551

Rev. B | Page 33 of 40

Address

Bit

Bit Name

Description

0x0C

Unused

Unused.

CP offset current polarity

Selects the polarity of the charge pump offset current of the output PLL.

0 = pump up (default).

1 = pump down.

This bit is ineffective unless Bit 3 = 1.

[5:4]

CP offset current

Controls the magnitude of the charge pump offset current of the output PLL as a

fraction of the value in Register 0x0A. Ineffective unless Bit 3 = 1.

00 = 1/2 (default).

01 = 1/4.

10 = 1/8.

11 = 1/16.

Enable CP offset current control

Controls functionality of Bits[6:4].

0 = the device automatically controls charge pump offset current (default).

1 = charge pump offset current defined by Bits[6:4].

Reserved

Enables PFD up divide-by-2 (reserved for test).

Reserved

Enables PFD down divide-by-2 (reserved for test).

Reserved

Enables feedback divide-by-2 (reserved for test).

0x0D

[7:6]

Antibacklash control

Controls the PFD antibacklash period of the output PLL.

00 = minimum (default).

01 = low.

10 = high.

11 = maximum.

These bits are ineffective unless Register 0x0B[6] = 1.

[5:1]

Unused

Unused.

Output PLL lock detector

power-down

Controls power-down of the output PLL’s lock detector.

0 = lock detector active (default).

1 = lock detector powered down.

VCO Control (Register 0x0E to Register 0x10)

Table 25.

Address

Bit

Bit Name

Description

0x0E

Calibrate VCO

Initiates VCO calibration (this is an autoclearing bit). This bit is ineffective unless Bit 2 = 1.

Enable automatic level control

Enables automatic level control of the VCO.

0 = VCO level defined by Register 0x0F[7:2].

1 = the device automatically controls the VCO level (default).

[5:3]

Automatic level control

threshold

Controls the VCO threshold detector level. The default is 110. Note that the function-

ality of Bit 4 is inverted; that is, the minimum is 010, and the maximum is 101.

Enable SPI control of VCO

calibration

Enables functionality of Bit 7.

0 = the device automatically performs VCO calibration (default).

1 = Bit 7 controls VCO calibration.

Boost VCO supply

Selects VCO supply voltage.

0 = normal supply voltage (default).

1 = increase supply voltage by 100 mV.

Enable SPI control of VCO band

setting

Controls VCO band setting functionality.

0 = the device automatically selects the VCO band (default).

1 = VCO band defined by Register 0x10[7:1].

0x0F

[7:2]

VCO level control

Controls the VCO amplitude from minimum (00 0000) to maximum (11 1111). The

default is 10 0000. These bits are ineffective unless Register 0x0E[6] = 0.

[1:0]

Unused

Unused.

0x10

[7:1]

VCO band control

Controls the VCO frequency band from minimum (000 0000) to maximum (111 1111).

The default is 100 0000.

Unused

Unused.

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