ADF4155 datasheet(23/32 Pages) AD

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Data Sheet

ADF4155

With Bits[C4:C1] set to 0110, Register 6 is programmed. Figure 30

shows the input data format for programming this register.

Reference Input (REFIN) Mode

When DB30 is set to 1, differential mode is used on the

reference input. When this bit is set to 0, single-ended mode is

used on the reference input.

RF Divider Select

Bits[DB23:DB21] select the value of the RF output divider (see

Figure 30).

Bleed Current Settings

Enabling the constant negative bleed (DB12) is the recommended

default mode to optimize the PLL in-band phase noise and spur

performance. Constant negative bleed works by adding a constant

offset to the charge pump and, therefore, improves its linearity.

Bits[DB20:DB13] and DB12 are used to control the amount of

constant negative bleed current.

Bits[DB20:DB13] set the value of this bleed current with a

resolution of 3.75 µA. The correct value of bleed current (IBLEED)

depends on the programmed charge pump current (ICP) and the

N counter value and must be calculated with following formula:

IBLEED = 6 × ICP/N

The closest higher value must be chosen with the bleed current

setting bits.

Constant Negative Bleed Current

When set to 1, Bit DB12 enables the constant negative bleed

current. When set to 0, it disables the constant negative bleed

current.

Mute Till Lock Detect (MTLD)

When DB11 is set to 1, the supply current to the RF output stage

is shut down until the device achieves lock, as measured by the

digital lock detect circuitry.

RF Output Enable

The DB6 bit enables or disables the RF output. If DB5 is set to 0,

the RF output is disabled. If DB5 is set to 1, the RF output is

enabled.

Output Power

Bits[DB5:DB4] set the value of the RF output power level (see

Figure 30).

Figure 30. Register 6 (R6)

OUTPUT POWER

–4dBm

–1dBm

+2dBm

+5dBm

D12

D11

RF DIVIDER

SELECT

÷1

÷2

÷4

÷8

D10

÷16

÷32

÷64

OUTPUT

POWER

DIVIDER

SELECT

DB31

DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13

DB12

DB11 DB10

DB9

DB8 DB7 DB6

DB5

DB4

DB3

DB2

DB1

DB0

CONTROL BITS

D12

D11

D10

BL8

BL7

BL6

BL5

BL4

BL3

BL2

BL1

BLE

C3(1) C2(1) C1(0)

C4(0)

BLEED CURRENT SETTINGS

DBB 1

1DBB = DOUBLE BUFFERED BITS—BUFFERED BY THE WRITE TO REGISTER 0 IF, AND ONLY IF, DB14 OF REGISTER 4 IS HIGH.

MUTE TILL

LOCK DETECT

MUTE DISABLED

MUTE ENABLED

RF OUTPUT

ENABLE

DISABLED

ENABLED

RM1

REFERENCE

INPUT MODE

SINGLE-ENDED

DIFFERENTIAL

RESERVED

BL8

BL7

..........

BL2

BL1

BLEED CURRENT SETTINGS

0 × 3.75µA = 0µA

1 × 3.75µA = 3.75µA

2 × 3.75µA = 7.50µA

3 × 3.75µA = 11.25µA

253 × 3.75µA = 948.75µA

254 × 3.75µA = 952.50µA

255 × 3.75µA = 956.25µA

BLE

CONSTANT NEGATIVE

BLEED CURRENT ENABLE

DISABLED

ENABLED

DB30 DB29 DB28 DB27 DB26 DB25 DB24

RM1

RESERVED

Rev. 0 | Page 23 of 32

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