Datasheet

Data Sheet ADF4159
Rev. D | 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 WORDRESERVED
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
00000000SSE1S20S19S18S17S16S15S14S13S12S11S10S9S8S7S6S5 C3(1)C2(1)C1(0)
S20 S19
...
S2 S1 STEP WORD
00 ...00 0
00 ...01 1
00 ...10 2
00 ...11 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
STEP SELSSE1
0STEPWORD1
1STEPWORD2
10849-026
Figure 31. Step Register (R6) Map