RFM63B Datasheet, PDF (15/90 Pages) List of Unclassifed Manufacturers – ISM TRANSCEIVER MODULE V1.1

ADVANCED COMMUNICATIONS & SENSING
, the PLL prototype is the following:
• 64 ≤ R ≤ 169
• S < P+1
• PLLBW = 15 kHz nominal
• Startup times and reference frequency spurs as specified.
RFM63B
3.2.5. Voltage Controlled Oscillator
The integrated VCO requires only two external tank circuit inductors. As the input is differential, the two inductors
should have the same nominal value. The performance of these components is important for both the phase noise
and the power consumption of the PLL. It is recommended that a pair of high Q factor inductors is selected. These
should be mounted orthogonally to other inductors (in particular the PA choke) to reduce spurious coupling
between the PA and VCO. In addition, such measures may reduce radiated pulling effects and undesirable
transient behavior, thus minimizing spectral occupancy. Note that ensuring a symmetrical layout of the VCO
inductors will further improve PLL spectral purity.
For best performance wound type inductors, with tight tolerance, should be used as described in section 7.5.3.
3.2.5.1. SW Settings of the VCO
To guarantee the optimum operation of the VCO over the RF63‟s frequency and temperature ranges, the
following settings should be programmed into the RF63:
Target channel
(MHz)
Freq_band
863-
870
10
902-
915
00
915-
928
01
950-
960
10
Table 10: MCParam_Freq_band Setting
3.2.5.2. Trimming the VCO Tank by Hardware and Software
To ensure that the frequency band of operation may be accurately addressed by the R, P and S dividers of the
synthesizer, it is necessary to ensure that the VCO is correctly centered. Note that for the reference design (see
section 7.5) no centering is necessary. However, any deviation from the reference design may require the
optimization procedure, outlined below, to be implemented. This procedure is simplified thanks to the built-in VCO
trimming feature which is controlled over the SPI interface. This tuning does not require any RF test equipment,
and can be achieved by simply measuring Vtune, the voltage between pin LFM and LFP.
The VCO is centered if the voltage is within the range:
50≤ Vtune(mV ) ≤150
Note that this measurement should be conducted when in transmit mode at the center frequency of the desired
band (for example ~867 MHz in the 863-870 MHz band), with the appropriate MCParam_Freq_band setting.
If this inequality is not satisfied then adjust the MCParam_VCO_trim bits from 00 whilst monitoring Vtune. This
allows the VCO voltage to be trimmed in + 60 mV increments. Should the desired voltage range be inaccessible,
the voltage may be adjusted further by changing the tank circuit inductance value. Note that an increase in
inductance will result in an increase Vtune.
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