AD9520-3SLASHPCBZ datasheet(68/84 Pages) AD

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AD9520-3

Rev. 0 | Page 68 of 84

Table 53. PLL

Reg.

Addr

(Hex) Bit(s) Name

Description

010

[7]

PFD polarity

Sets the PFD polarity. Negative polarity is for use (if needed) with external VCO/VCXO only.

The on-chip VCO requires positive polarity [7] = 0.

[7] = 0; positive (higher control voltage produces higher frequency) (default).

[7] = 1; negative (higher control voltage produces lower frequency).

010

[6:4]

CP current

Charge pump current (with CPRSET = 5.1 kΩ).

[6]

[5]

[4]

ICP (mA)

0.6

1.2

1.8

2.4

3.0

3.6

4.2

4.8 (default)

010

[3:2]

CP mode

Charge pump operating mode.

[3]

[2]

Charge Pump Mode

High impedance state.

Force source current (pump up).

Force sink current (pump down).

Normal operation (default).

010

[1:0]

PLL power-

down

PLL operating mode.

[1]

[0]

Mode

Normal operation; this mode must be selected to use the PLL.

Asynchronous power-down (default).

Unused.

Synchronous power-down.

011

[7:0]

14-bit R counter,

Bits[7:0] (LSB)

Reference divider LSBs—lower eight bits. The reference divider (also called the R divider or R counter) is

14 bits long. The lower eight bits are in this register (default: 0x01).

012

[5:0]

14-bit R counter,

Bits[13:8] (MSB)

Reference divider MSBs—upper six bits. The reference divider (also called the R divider or R counter) is

14 bits long. The upper six bits are in this register (default: 0x00).

013

[5:0]

6-bit A counter

A counter (part of N divider). The N divider is also called the feedback divider (default: 0x00).

014

[7:0]

13-bit B counter,

Bits[7:0] (LSB)

B counter (part of N divider)—lower eight bits. The N divider is also called the feedback divider (default: 0x03).

015

[4:0]

13-bit B counter,

Bits[12:8] (MSB)

B counter (part of N divider)—upper five bits. The N divider is also called the feedback divider (default: 0x00).

016

[7]

Set CP pin

to VCP/2

Sets the CP pin to one-half of the VCP supply voltage.

[7] = 0; CP normal operation (default).

[7] = 1; CP pin set to VCP/2.

016

[6]

Reset R counter

Reset R counter (R divider).

[6] = 0; normal (default).

[6] = 1; hold R counter in reset.

016

[5]

Reset A and B

counters

Reset A and B counters (part of N divider).

[5] = 0; normal (default).

[5] = 1; hold A and B counters in reset.

016

[4]

Reset all

counters

Reset R, A, and B counters.

[4] = 0; normal (default).

[4] = 1; hold R, A, and B counters in reset.

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