ADF4360-3 Analog Devices, ADF4360-3 Datasheet - Page 19

• Manufacturer Part Number: ADF4360-3
• Description: Integrated Synthesizer and VCO
• Manufacturer: Analog Devices

FIXED FREQUENCY LO
Figure 17 shows the ADF4360-3 used as a fixed frequency LO at
1.8 GHz. The low-pass filter was designed using ADIsimPLL for
a channel spacing of 8 MHz and an open-loop bandwidth of
40 kHz. The maximum PFD frequency of the ADF4360-3 is
8 MHz. Since using a larger PFD frequency allows users to use a
smaller N, the in-band phase noise is reduced to as low as pos-
sible, –99 dBc/Hz. The 40 kHz bandwidth is chosen to be just
greater than the point at which the open-loop phase noise of the
VCO is –99 dBc/Hz, thus giving the best possible integrated
noise. The typical rms phase noise (100 Hz to 100 kHz) of the
LO in this configuration is 0.3°. The reference frequency is from
a 16 MHz TCXO from Fox; thus an R value of 2 is programmed.
Taking into account the high PFD frequency and its effect on
the band select logic, the band select clock divider is enabled. In
this case, a value of 8 is chosen. A very simple pull-up resistor
and dc blocking capacitor complete the RF output stage.
POWER-UP
After power-up, the part needs three writes for normal opera-
tion. The correct sequence is to the R counter latch, followed by
the control latch, and N counter latch.
INTERFACING
The ADF4360 family has a simple SPI® compatible serial inter-
face for writing to the device. CLK, DATA, and LE control the
data transfer. When LE goes high, the 24 bits that have been
clocked into the appropriate register on each rising edge of CLK
will get transferred to the 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 the maximum update rate possible is 833 kHz or one
update every 1.2 µs. This is certainly more than adequate for
systems that will have typical lock times in hundreds of micro-
seconds.
801BE-160
16MHz
FOX
1nF
10µF
1nF
4.7kΩ
1nF
51Ω
14
16
17
18
19
12
13
CPGND
C
REF
CLK
DATA
LE
C
R
1
V
V
N
C
SET
VCO
VCO
6
Figure 17. Fixed Frequency LO
IN
3
DV
8
21
DD
AGND
9
ADF4360-3
AV
V
VDD
2
10
DD
11
CE MUXOUT
23
22
DETECT
LOCK
DGND RF
15
20
RF
V
OUT
OUT
TUNE
CP
A
B
24
7
4
5
V
3.9nF
VCO
51Ω
470Ω
22.0nF
51Ω
100pF
100pF
Rev. 0 | Page 19 of 24
ADuC812 Interface
Figure 18 shows the interface between the ADF4360 family 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 ADF4360 family
needs a 24-bit word, which is accomplished by writing three
8-bit bytes from the MicroConverter to the device. When the
third byte has been written, the LE input should be brought
high to complete the transfer.
I/O port lines on the ADuC812 are also used to control power-
down (CE input) and detect lock (MUXOUT configured as lock
detect and polled by the port input). When operating in the
described mode, the maximum SCLOCK rate of the ADuC812
is 4 MHz. This means that the maximum rate at which the out-
put frequency can be changed is 166 kHz.
ADSP-2181 Interface
Figure 19 shows the interface between the ADF4360 family and
the ADSP-21xx digital signal processor. The ADF4360 family
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 fram-
ing. 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 loca-
tions for each 24-bit word. To program each 24-bit latch, store
the 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
ADuC812
I/O PORTS
I/O PORTS
Figure 19. ADSP-21xx to ADF4360-x Interface
SCLOCK
SCLOCK
Figure 18. ADuC812 to ADF4360-x Interface
MOSI
MOSI
TFS
SCLK
SDATA
CE
MUXOUT
(LOCK DETECT)
SCLK
SDATA
CE
MUXOUT
(LOCK DETECT)
LE
LE
ADF4360-x
ADF4360-x
ADF4360-3