ADF4106BRUZ View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

ADF4106BRUZ

PLL Frequency Synthesizer

Analog Devices 

Data Sheet

THE FUNCTION LATCH

With C2 and C1 set to 1 and 0, respectively, the on-chip

function latch is programmed. Table 9 shows the input data

format for programming the function latch.

Counter Reset

DB2 (F1) is the counter reset bit. When this is 1, the R counter

and the N (A, B) counter are reset. For normal operation, this

bit should be 0. When powering up, disable the F1 bit (set to 0).

The N counter will then resume counting in close alignment

with the R counter. (The maximum error is one prescaler cycle).

Power-Down

DB3 (PD1) and DB21 (PD2) provide programmable power-

down modes. They are enabled by the CE pin.

When the CE pin is low, the device is immediately disabled

regardless of the states of PD2, PD1.

In the programmed asynchronous power-down, the device

powers down immediately after latching 1 into the PD1 bit,

with the condition that PD2 is loaded with 0.

In the programmed synchronous power-down, the device

power-down is gated by the charge pump to prevent unwanted

frequency jumps. Once the power-down is enabled by writing 1

into the PD1 bit (provided that 1 has also been loaded to PD2),

then the device goes into power-down during the next charge

pump event.

When a power-down is activated (either synchronous or

asynchronous mode, including CE pin activated power-down),

the following events occur:

• All active dc current paths are removed.

• The R, N, and timeout counters are forced to their load state

conditions.

• The charge pump is forced into three-state mode.

• The digital clock detect circuitry is reset.

• The RFIN input is debiased.

• The reference input buffer circuitry is disabled.

• The input register remains active and capable of loading and

latching data.

MUXOUT Control

The on-chip multiplexer is controlled by M3, M2, and M1 on

the ADF4106 family. Table 9 shows the truth table.

Fastlock Enable Bit

DB9 of the function latch is the fastlock enable bit. When this

bit is 1, fastlock is enabled.

ADF4106

Fastlock Mode Bit

DB10 of the function latch is the fastlock mode bit. When

fastlock is enabled, this bit determines which fastlock mode is

used. If the fastlock mode bit is 0, then Fastlock Mode 1 is

selected; and if the fastlock mode bit is 1, then Fastlock Mode 2

is selected.

Fastlock Mode 1

The charge pump current is switched to the contents of Current

Setting 2. The device enters fastlock when 1 is written to the CP

gain bit in the N (A, B) counter latch. The device exits fastlock

when 0 is written to the CP gain bit in the N (A, B) counter

latch.

Fastlock Mode 2

The charge pump current is switched to the contents of Current

Setting 2. The device enters fastlock when 1 is written to the CP

gain bit in the N (A, B) counter latch. The device exits fastlock

under the control of the timer counter. After the timeout

period, which is determined by the value in TC4 to TC1, the CP

gain bit in the N (A, B) counter latch is automatically reset to 0,

and the device reverts to normal mode instead of fastlock. See

Table 9 for the timeout periods.

Timer Counter Control

The user has the option of programming two charge pump

currents. The intent is that Current Setting 1 is used when the

RF output is stable and the system is in a static state. Current

Setting 2 is used when the system is dynamic and in a state of

change (that is, when a new output frequency is programmed).

The normal sequence of events follows.

The user initially decides what the preferred charge pump

currents are going to be. For example, the choice may be

2.5 mA as Current Setting 1 and 5 mA as the Current Setting 2.

Simultaneously, the decision must be made as to how long the

secondary current stays active before reverting to the primary

current. This is controlled by the timer counter control bits,

DB14 to DB11 (TC4 to TC1), in the function latch. The truth

table is given in Table 9.

To program a new output frequency, simply program the N (A,

B) counter latch with new values for A and B. Simultaneously,

the CP gain bit can be set to 1, which sets the charge pump with

the value in CPI6 to CPI4 for a period of time determined by

TC4 to TC1. When this time is up, the charge pump current

reverts to the value set by CPI3 to CPI1. At the same time, the

CP gain bit in the N (A, B) counter latch is reset to 0 and is now

ready for the next time the user wishes to change the frequency.

Note that there is an enable feature on the timer counter. It is

enabled when Fastlock Mode 2 is chosen by setting the fastlock

mode bit (DB10) in the function latch to 1.

Rev. E | Page 17 of 24

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