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ADF4111
(Rev.:Rev0)

RF PLL Frequency Synthesizers

Analog Devices 

ADF4110/ADF4111/ADF4112/ADF4113

THE FUNCTION LATCH

With C2, C1 set to 1, 0, the on-chip function latch will be pro-

grammed. Table V 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 A, B counters are reset. For normal operation this bit

should be “0.” Upon powering up, the F1 bit needs to be disabled,

the N counter resumes counting in “close” alignment with the R counter.

(The maximum error is one prescaler cycle.)

Power-Down

DB3 (PD1) and DB21 (PD2) on the ADF4110 family, 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 pow-

ers down immediately after latching a “1” into bit PD1, with the

condition that PD2 has been loaded with a “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 a “1” into

bit PD1 (on condition that a “1” has also been loaded to PD2),

the device will go into power-down on the occurrence of the next

charge pump event.

When a power-down is activated (either synchronous or asynchro-

nous 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, M1 on the

ADF4110 family. Table V shows the truth table.

Fastlock Enable Bit

DB9 of the Function Latch is the Fastlock Enable Bit. Only

when this is “1” is Fastlock enabled.

Fastlock Mode Bit

DB10 of the Function Latch is the Fastlock Enable 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 by having a “1” written to the CP

Gain bit in the AB counter latch. The device exits Fastlock by

having a “0” written to the CP Gain bit in the AB counter latch.

Fastlock Mode 2

The charge pump current is switched to the contents of Current

Setting 2.

The device enters Fastlock by having a “1” written to the CP

Gain bit in the AB counter latch. The device exits Fastlock under

the control of the Timer Counter. After the timeout period deter-

mined by the value in TC4–TC1, the CP Gain bit in the AB

counter latch is automatically reset to “0” and the device reverts

to normal mode instead of Fastlock. See Table V for the time-

out periods.

Timer Counter Control

The user has the option of programming two charge pump cur-

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

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

Setting 2 is meant to be used when the system is dynamic

and in a state of change (i.e., when a new output frequency is

programmed).

The normal sequence of events is as follows:

The user initially decides what the preferred charge pump cur-

rents are going to be. For example, they may choose 2.5 mA as

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

At the same time, they must also decide how long they want the

secondary current to stay active before reverting to the primary

current. This is controlled by the Timer Counter Control Bits

DB14 to DB11 (TC4–TC1) in the Function Latch. The truth

table is given in Table V.

When the user wishes to program a new output frequency, he

can simply program the AB counter latch with new values for A

and B. At the same time, he can set the CP Gain bit to a “1,”

which sets the charge pump with the value in CPI6–CPI4 for a

period of time determined by TC4–TC1. When this time is up,

the charge pump current reverts to the value set by CPI3– CPI1.

At the same time the CP Gain bit in the A, B Counter latch is

reset to 0 and is now ready for the next time the user wishes

to change the frequency again.

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.”

Charge Pump Currents

CPI3, CPI2, CPI1 program Current Setting 1 for the charge

pump. CPI6, CPI5, CPI4 program Current Setting 2 for the

charge pump. The truth table is given in Table V.

Prescaler Value

P2 and P1 in the Function Latch set the prescaler values. The

prescaler value should be chosen so that the prescaler output

frequency is always less than or equal to 200 MHz. Thus, with

an RF frequency of 2 GHz, a prescaler value of 16/17 is valid

but a value of 8/9 is not.

PD Polarity

This bit sets the PD Polarity Bit. See Table V.

CP Three-State

This bit the CP output pin. With the bit set high, the CP output

is put into three-state. With the bit set low, the CP output is

enabled.

REV. 0

–17–

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