ADF4372 datasheet(22/47 Pages) AD

22 / 47 page

ADF4372

Data Sheet

Rev. 0 | Page 22 of 47

DEVICE SETUP

The recommended sequence of steps to set up the ADF4372 are

as follows:

1. Set up the SPI interface.

2. Perform the initialization sequence.

3. Perform the frequency update sequence.

STEP 1: SET UP THE SPI INTERFACE

First, initialize the SPI. Write the values in Table 7 to Address 0x00

and Address 0x01.

Table 7. SPI Interface Setup

Address

Setting

Notes

0x00

0x18

4-wire SPI

0x01

0x00

Stalling, master readback control

STEP 2: INITIALIZATION SEQUENCE

Write to each register in reverse order from Address 0x7C to

Address 0x10. Choosing appropriate values to generate the desired

frequency. The registers that are not given in the datasheet can

be skipped in normal SPI mode. If SPI stream mode is used, write

0x00 to the registers not listed in the Register Summary section.

The frequency update sequence follows to generate the desired

output frequency.

STEP 3: FREQUENCY UPDATE SEQUENCE

Frequency updates require updating MOD2, FRAC1, FRAC2,

and INT. Therefore, the update sequence must be as follows:

1. Address 0x1A (new MOD2WORD[13:8])

2. Address 0x19 (new MOD2WORD[7:0])

3. Address 0x18 (new FRAC2WORD[13:7])

4. Address 0x17 (new FRAC2WORD[6:0])

5. Address 0x16 (new FRAC1WORD[23:16])

6. Address 0x15 (new FRAC1WORD[15:8])

7. Address 0x14 (new FRAC1WORD[7:0])

8. Address 0x11 (new BIT_INTEGER_WORD[15:8])

9. Address 0x10 (new BIT_INTEGER_WORD[7:0])

The frequency change occurs on the write to Address 0x10.

The unchanged registers do not need to be updated. For

example, for an integer-N PLL configuration (fractional parts are

not used), skip Step 1 to Step 7. In this case, the only required

updates are Address 0x11 and Address 0x10.

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