ADF4153BCPZ datasheet(21/24 Pages) AD

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Data Sheet

ADF4153

Rev. F | Page 21 of 24

When operating in this mode, the maximum SCLOCK rate of

the ADuC812 is 4 MHz. This means that the maximum rate at

which the output frequency can be changed is 180 kHz.

ADSP-21xx Interface

Figure 19 shows the interface between the ADF4153 and the

ADSP-21xx digital signal processor. As discussed previously,

the ADF4153 needs a 24-bit serial word for each latch write.

The easiest way to accomplish this using the ADSP-21xx family

is to use the autobuffered transmit mode of operation with

alternate framing. This provides a means for transmitting an

entire block of serial data before an interrupt is generated.

Set up the word length for eight bits and use three memory

locations for each 24-bit word. To program each 24-bit latch,

store the three 8-bit bytes, enable the autobuffered mode, and

write to the transmit register of the DSP. This last operation

initiates the autobuffer transfer.

ADSP-21xx

ADF4153

SCLK

CLK

DATA

MUXOUT

(LOCK DETECT)

TFS

I/O FLAGS

Figure 19. ADSP-21xx to ADF4153 Interface

PCB DESIGN GUIDELINES FOR CHIP SCALE

PACKAGE

The lands on the chip scale package (CP-20) are rectangular.

The printed circuit board (PCB) pad for these should be 0.1 mm

longer than the package land length and 0.05 mm wider than

the package land width. The land should be centered on the

pad. This ensures that the solder joint size is maximized.

The bottom of the chip scale package has a central thermal pad.

The thermal pad on the PCB should be at least as large as this

exposed pad. On the PCB, there should be a clearance of at least

0.25 mm between the thermal pad and the inner edges of the

pad pattern. This ensures that shorting is avoided.

Thermal vias can be used on the PCB thermal pad to improve

thermal performance of the package. If vias are used, they should

be incorporated in the thermal pad at 1.2 mm pitch grid. The

via diameter should be between 0.3 mm and 0.33 mm, and the

via barrel should be plated with one ounce of copper to plug the

via. The user should connect the PDB thermal pad to AGND.

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