Data Sheet

ADF4159

Rev. E | Page 23 of 36

STEP REGISTER (R6) MAP

When Bits DB[2:0] are set to 110, the on-chip step register

(Register R6) is programmed (see Figure 31).

Reserved Bits

All reserved bits must be set to 0 for normal operation.

Step Select

When Bit DB23 is set to 0, Step Word 1 is selected. When

Bit DB23 is set to 1, Step Word 2 is selected.

20-Bit Step Word

Bits DB[22:3] determine the step word. The step word is the

number of steps in the ramp.

DB31

20-BIT STEP WORD

RESERVED

CONTROL

BITS

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

SSE1 S20

S19

S18

S17

S16

S15

S14

S13

S12

S11

S10

S9

S8

S7

S6

S5

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

S20

S19

...

S2

S1

STEP WORD

0

0

...

0

0

0

0

0

...

0

1

1

0

0

...

1

0

2

0

0

...

1

1

3

.

.

...

.

.

.

.

.

...

.

.

.

.

.

...

.

.

.

1

1

...

0

0

1,048,572

1

1

...

0

1

1,048,573

1

1

...

1

0

1,048,574

1

1

...

1

1

1,048,575

S4

S3

S1

S2

STEP SEL

SSE1

0

STEP WORD 1

1

STEP WORD 2

Figure 31. Step Register (R6) Map