ADF4112BCPZ datasheet(20/28 Pages) AD

20 / 28 page

ADF4110/ADF4111/ADF4112/ADF4113

Data Sheet

Rev. F | Page 20 of 28

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, and CPI1 program Current Setting 1 for the charge

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

charge pump. The truth table is given in Table 10.

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 phase detector polarity bit. See Table 10.

CP Three-State

This bit controls 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.

INITIALIZATION LATCH

When C2, C1 = 1, 1, the initialization latch is programmed.

This is essentially the same as the function latch (programmed

when C2, C1 = 1, 0).

However, when the initialization latch is programmed, an addi-

tional internal reset pulse is applied to the R and AB counters.

This pulse ensures that the AB counter is at load point when the

AB counter data is latched, and the device begins counting in

close phase alignment.

If the latch is programmed for synchronous power-down (CE

pin high; PD1 bit high; PD2 bit low), the internal pulse also

triggers this power-down. The prescaler reference and the

oscillator input buffer are unaffected by the internal reset pulse,

so close phase alignment is maintained when counting resumes.

When the first AB counter data is latched after initialization, the

internal reset pulse is again activated. However, successive AB

counter loads after this will not trigger the internal reset pulse.

DEVICE PROGRAMMING AFTER INITIAL

POWER-UP

After initial power-up of the device, there are three ways to

program the device.

Initialization Latch Method

Apply VDD. Program the initialization latch (11 in 2 LSBs of

input word). Make sure the F1 bit is programmed to 0. Then, do

an R load (00 in 2 LSBs). Then do an AB load (01 in 2 LSBs).

When the initialization latch is loaded, the following occurs:

1. The function latch contents are loaded.

2. An internal pulse resets the R, A, B, and timeout counters

to load state conditions and three-states the charge pump.

Note that the prescaler band gap reference and the oscil-

lator input buffer are unaffected by the internal reset pulse,

allowing close phase alignment when counting resumes.

3. Latching the first AB counter data after the initialization

word activates the same internal reset pulse. Successive AB

loads do not trigger the internal reset pulse unless there is

another initialization.

CE Pin Method

1. Apply VDD.

2. Bring CE low to put the device into power-down. This is an

asynchronous power-down in that it happens immediately.

3. Program the function latch (10). Program the R counter

latch (00). Program the AB counter latch (01).

4. Bring CE high to take the device out of power-down. The R

and AB counters now resume counting in close alignment.

After CE goes high, a duration of 1 µs may be required for the

prescaler band gap voltage and oscillator input buffer bias to

reach steady state.

CE can be used to power the device up and down in order to

check for channel activity. The input register does not need to

be reprogrammed each time the device is disabled and enabled

as long as it has been programmed at least once after VDD was

initially applied.

Counter Reset Method

1. Apply VDD.

2. Do a function latch load (10 in 2 LSBs). As part of this,

load 1 to the F1 bit. This enables the counter reset.

3. Do an R counter load (00 in 2 LSBs). Do an AB counter

load (01 in 2 LSBs). Do a function latch load (10 in 2

LSBs). As part of this, load 0 to the F1 bit. This disables the

counter reset.

This sequence provides the same close alignment as the initiali-

zation method. It offers direct control over the internal reset.

Note that counter reset holds the counters at load point and

three states the charge pump but does not trigger synchronous

power-down. The counter reset method requires an extra

function latch load compared to the initialization latch method.

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