ADF4106BCPZ-R7 datasheet(20/24 Pages) AD

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ADF4106

Data Sheet

Rev. E | Page 20 of 24

INTERFACING

The ADF4106 has a simple SPI-compatible serial interface for

writing to the device. CLK, DATA, and LE control the data

transfer. When LE goes high, the 24 bits clocked into the input

appropriate latch. See Figure 2 for the timing diagram and

Table 5 for the latch truth table.

The maximum allowable serial clock rate is 20 MHz. This

means that the maximum update rate for the device is 833 kHz,

or one update every 1.2 µs. This is certainly more than adequate

for systems that have typical lock times in hundreds of

microseconds.

ADuC812 Interface

Figure 23 shows the interface between the ADF4106 and the

ADuC812 MicroConverter®. Since the ADuC812 is based on an

8051 core, this interface can be used with any 8051-based

microcontroller. The MicroConverter is set up for SPI master

mode with CPHA = 0. To initiate the operation, the I/O port

driving LE is brought low. Each latch of the ADF4106 needs a

24-bit word. This is accomplished by writing three 8-bit bytes

from the MicroConverter to the device. When the third byte

is written, the LE input should be brought high to complete

the transfer.

On first applying power to the ADF4106, it needs four writes

(one each to the initialization latch, function latch, R counter

latch, and N counter latch) for the output to become active.

I/O port lines on the ADuC812 are also used to control

power-down (CE input) and to detect lock (MUXOUT

configured as lock detect and polled by the port input).

When operating in the mode described, 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 166 kHz.

CLK

DATA

MUXOUT

(LOCK DETECT)

MOSI

ADF4106

SCLOCK

I/O PORTS

ADuC812

Figure 23. ADuC812-to-ADF4106 Interface

ADSP2181 Interface

Figure 24 shows the interface between the ADF4106 and the

ADSP21xx digital signal processor (DSP). The ADF4106

needs a 24-bit serial word for each latch write. The easiest way

to accomplish this using the ADSP21xx 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 8 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.

CLK

DATA

MUXOUT

(LOCK DETECT)

MOSI

ADF4106

SCLOCK

I/O FLAGS

ADSP-21xx

TFS

Figure 24. ADSP-21xx-to-ADF4106 Interface

PCB DESIGN GUIDELINES FOR CHIP SCALE

PACKAGE

The lands on the LFCSP (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 LFCSP 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 may 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 1 oz. copper to plug the via.

The user should connect the PCB thermal pad to AGND.

ADF4106BCPZ-R7 Datasheet(PDF) 20 Page - Analog Devices

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