EVAL-ADF70XXEKZ1 Analog Devices Inc, EVAL-ADF70XXEKZ1 Datasheet - Page 17

• Manufacturer Part Number: EVAL-ADF70XXEKZ1
• Description: KIT DEV ADF702X FOR BF533EZKIT
• Manufacturer: Analog Devices Inc
• Type: Transceiver, ISMr

Specifications of EVAL-ADF70XXEKZ1

• Frequency: 431MHz ~ 464MHz, 862MHz ~ 870MHz, 902MHz ~ 928MHz
• For Use With/related Products: ADF702x
• For Use With: EVAL-ADF70XXMBZ2 - MOTHER BOARD FOR ADISIMLINK DEV
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

VCO Bias Current
VCO bias current can be adjusted using Bit R1_DB19 to
Bit R1_DB16. To ensure VCO oscillation under all conditions,
the minimum bias current setting is Setting 12 (0xC).
431 MHz to 464 MHz Operation
For operation in the 431 MHz to 464 MHz band, the frequency
divide-by-2 has to be enabled. It is enabled by R1_DB13. Because
this divide is external to the synthesizer loop, the feedback
divider number (N + F) should be programmed to a value twice
the desired RF output frequency.
LOOP FILTER
R1_DB (16:19)
VCO BIAS
CVCO PIN
220µF
VCO
Figure 24. Voltage Controlled Oscillator
÷2
VCO SELECT BIT
÷2
MUX
TO PA AND
N DIVIDER
Rev. A | Page 17 of 44
CHOOSING CHANNELS FOR BEST SYSTEM
PERFORMANCE
The Fractional-N PLL allows the selection of any channel
within 862 MHz to 928 MHz (and 431 MHz to 464 MHz using
divide-by-2) to a resolution of <300 Hz. This also facilitates
frequency-hopping systems.
Careful selection of the RF transmit channels must be made to
achieve best spurious performance. The architecture of
Fractional-N results in some level of the nearest integer channel
moving through the loop to the RF output. These beat-note
spurs are not attenuated by the loop, if the desired RF channel
and the nearest integer channel are separated by a frequency of
less than the LBW.
The occurrence of beat-note spurs is rare, because the integer
frequencies are at multiples of the reference, which is typically
>10 MHz.
Beat-note spurs can be significantly reduced in amplitude by
avoiding very small or very large values in the fractional
register, using the frequency doubler. By having a channel
1 MHz away from an integer frequency, a 100 kHz loop filter
can reduce the level to less than −45 dBc.
ADF7025