ADRF6702 Analog Devices, Inc., ADRF6702 Datasheet - Page 10

• Manufacturer Part Number: ADRF6702
• Description: 1550 Mhz To 2150 Mhz Quadrature Modulator With Integrated Fractional-n Pll And Vco
• Manufacturer: Analog Devices, Inc.

ADRF6702
DEVICE PROGRAMMING
Device programming is effected using a three pin SPI port. The
description of timing requirements for the SPI port is given in
Figure 2. There are eight programmable registers, each with 24
bits, controlling the operation of the device. The register
functions can be broken down as follows;
Register 0 – Integer control for the PLL.
Register 1 – Modulus control for PLL.
Register 2 – Fractional control for PLL.
Register 3 – Sigma Delta Function
Register 4 – PLL Charge pump, PFD, reference path control
Register 5 – LO path and modulator control
Register 6 – VCO controls and VCO enable functions
Register 7 – Modulator bias enable, external VCO enable
Note - The PLL has internal calibration that must be run when
the device is programmed with a given frequency. This
calibration is automatically run whenever registers 0, 1, or 2 are
programmed. Because the other registers affect PLL
performance, the lower three registers should always be
programmed last, preferably in the order 0, 1, 2.
Software is available on the Analog Devices website
(www.analog.com) that allows easy programming from a PC
running Windows XP
REGISTER 0 INTEGER DIVIDE CONTROL
With R0[2:0] set to 000, the on-chip integer divide control
register is programmed as shown in figure 39.
INTEGER DIVIDE RATIO
The integer divide ratio is used to set the INT value in Equation 1.
The INT, FRAC, and MOD values make it possible to generate
output frequencies that are spaced by fractions of the PFD
frequency. The VCO frequency (F
Where:
F
INT is the preset integer divide ratio value (24 to 119 in
fractional mode).
MOD is the preset fractional modulus (1 to 2047).
FRAC is the preset fractional divider ratio value (0 to MOD-1).
VCO
F
is the output frequency of the internal VCO.
VCO
= 2 × f
PFD
× (INT + (FRAC/MOD))
™
.
VCO
) equation is:
Rev. PrE | Page 10 of 18
(1)
DIVIDE MODE
Divide mode determines whether fractional mode or integer
mode is used. In integer mode, the RF VCO output frequency
(F
where INT is the integer divide ratio value (21 to 123 in integer
mode).
VCO
F
) is calculated using the following equation:
VCO
= 2 × f
PFD
× (INT)
Preliminary Technical Data
(2)