REV. A

ADF4210/ADF4211/ADF4212/ADF4213

–17–

RF PROGRAM MODES

Table III and Table V show how to set up the Program Modes

in the ADF421x family.

RF Charge Pump Currents

RFCP2, RFCP1, RFCP0 program current setting for the RF

charge pump. See Table V.

PROGRAMMABLE RF N COUNTER

If control bits C2, C1 are 1, 1, the data in the input register is

used to program the RF N (A + B) counter. The N counter

consists of a 6-bit swallow counter (A Counter) and 12-bit

programmable counter (B Counter). Table IV shows the input

register data format for programming the RF N counter and the

possible divide ratios.

RF Prescaler Value

P14 and P15 in the RF A, B Counter Latch sets the RF pres-

caler value. See Table VI.

RF Power-Down

Table III and Table V show the power-down bits in the

ADF421x family.

RF Fastlock

The RF CP Gain bit (P17) of the RF N register in the ADF421x

family is the Fastlock Enable Bit. Only when this is “1” is IF

Fastlock enabled. When Fastlock is enabled, the RF CP current

is set to its maximum value. Also an extra loop filter damping

pensating for the change in loop characteristics while in Fastlock.

Since the RF CP Gain bit is contained in the RF N Counter, only

one write is needed to both program a new output frequency and

also initiate Fastlock. To come out of Fastlock, the RF CP Gain bit

on the RF N register must be set to “0.” See Table VI.

APPLICATIONS SECTION

Local Oscillator for GSM Handset Receiver

Figure 7 shows the ADF4210/ADF4211/ADF4212/ADF4213

being used with a VCO to produce the LO for a GSM base

station transmitter.

and, in this case, is terminated in 50

Ω. A typical GSM system

would have a 13 MHz TCXO driving the reference input with-

out any 50

Ω termination. In order to have a channel spacing of

200 kHz (the GSM standard), the reference input must be

divided by 65, using the on-chip reference.

WIDEBAND PLL

Many of the wireless applications for synthesizers and VCOs in

PLLs are narrowband in nature. These applications include

various wireless standards such as GSM, DSC1800, CDMA, or

WCDMA. In each of these cases, the total tuning range for the

local oscillator is less than 100 MHz. However, there are also

wideband applications where the local oscillator could have up

to an octave tuning range. For example, cable TV tuners have

a total range of about 400 MHz. Figure 8 shows an applica-

tion where the ADF4213 is used to control and program the

Micronetics M3500–1324. The loop filter was designed for an

RF output of 2100 MHz, a loop bandwidth of 40 kHz, a PFD

sitivity of the M3500–1324 at an output of 2100 MHz) and a

phase margin of 45

°C.

In narrowband applications, there is generally a small variation

(less than 10%) in output frequency and also a small variation

(typically < 10%) in VCO sensitivity over the range. However,

100pF

51

ADF4210/

ADF4211/

ADF4212/

ADF4213

5.6k

620pF

3.3k

8.2nF

VCO190-

902T

18

100pF

18

18

MUXOUT

LOCK

DETECT

100pF

CLK

DATA

LE

BEEN OMITTED FROM THE DIAGRAM TO AID CLARITY.

1.3nF

18

100pF

18

18

100pF

VCO190-

540T

3.3k

2.7k

100pF

51

1000pF

1000pF

51

1.3nF

5.6k

620pF

8.2nF

Figure 7. GSM Handset Receiver Local Oscillator Using the ADF4210/ADF4211/ADF4212/ADF4213