ADF5901

Data Sheet

Rev. A | Page 20 of 26

12-Bit Integer Value (INT)

These 12 bits (Bits[DB28:DB17]) set the INT value, which

determines the integer part of the RF division factor. This INT

value is used in Equation 5. See the RF Synthesis: a Worked

Example section for more information. All integer values from

75 to 4095 are allowed.

12-Bit MSB Fractional Value (FRAC)

These 12 bits (Bits[DB16:DB5]), together with Bits[DB17:DB5]

(FRAC LSB word) in Register R6, control what is loaded as the

FRAC value into the fractional interpolator. This FRAC value

partially determines the overall RF division factor. It is also used

in Equation 1. These 12 bits are the most significant bits (MSB)

of the 25-bit FRAC value, and Bits[DB17:DB5] (FRAC LSB

word) in Register R6 are the least significant bits (LSB). See the

RF Synthesis: a Worked Example section for more information.

REGISTER 6

Control Bits

With Bits[C5:C1] set to 00110, Register R6 is programmed.

Figure 25 shows the input data format for programming

this register.

13-Bit LSB FRAC Value

These 13 bits (Bits[DB17:DB5]), together with Bits[DB16:DB5]

(FRAC MSB word) in Register R5, control what is loaded as the

FRAC value into the fractional interpolator. This FRAC value

partially determines the overall RF division factor. It is also used

in Equation 1. These 13 bits are the least significant bits (LSB)

of the 25-bit FRAC value, and Bits[DB14:DB3] (FRAC MSB

word) in Register R5 are the most significant bits (MSB). See

the RF Synthesis: a Worked Example section for more

information.

Figure 25. Register 6 (R6)

DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4

DB3

DB2

DB1

DB0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

F12

F11

F10

F9

F8

F7

F6

F5

F4

F3

F2

F1

F0

C4(0) C3(1) C2(1) C1(0)

CONTROL

BITS

FRAC LSB WORD

C5(0)

F12

F11

..........

F1

F0

(FRAC)*

0

0

..........

0

0

0

0

0

..........

0

1

1

0

0

..........

1

0

2

0

0

..........

1

1

3

.

.

..........

.

.

.

.

.

..........

.

.

.

.

.

..........

.

.

.

1

1

..........

0

0

8188

1

1

..........

0

1

8189

1

1

..........

1

0

8190

1

1

.........

1

1

8191

*THE FRAC VALUE IS MADE UP OF THE 12-BIT MSB STORED IN

REGISTER R5, AND THE 13-BIT LSB REGISTER STORED IN

REGISTER R6. FRAC VALUE = 13-BIT LSB + 12-BIT MSB × 213.

FRAC LSB WORD

RESERVED