RFM42B-868-S1 QUASAR, RFM42B-868-S1 Datasheet - Page 27

• Manufacturer Part Number: RFM42B-868-S1
• Description: MODULE, TRANSMITTER, 20DB,SMD,868MHZ
• Manufacturer: QUASAR

Specifications of RFM42B-868-S1

• Modulation Type: FSK, GFSK, OOK
• Supply Voltage Range: 1.8V To 3.6V
• Supply Current: 85mA
• Interface Type: SPI
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

channel frequency, and channel spacing. The transmit modulation is applied directly
domain through the fractional divider which results in very precise accuracy and control over the transmit
deviation.
5. Internal Functional Blocks
This section provides an overview some of the key blocks of the internal radio architecture.
5.1. Synthesizer
An integrated Sigma Delta (ΣΔ) Fractional-N PLL synthesizer capable of operating from 240–960 MHz is provided
on-chip. Using a ΣΔ synthesizer has many advantages; it provides flexibility in
Depending on the part, the PLL and - modulator scheme is designed to support any desired frequency and
channel spacing in the range from 240–960 MHz with a frequency resolution of 156.25 Hz (Low band) or 312.5 Hz
(High band). The transmit data rate can be programmed between 0.123–256 kbps, and the frequency deviation
can be programmed between ±1–320 kHz. These parameters may be adjusted via registers as shown in "3.5.
Frequency Control".
The reference frequency to the PLL is 10 MHz. The PLL utilizes a differential L-C VCO, with integrated on-chip
inductors. The output of the VCO is followed by a configurable divider which will divide down the signal to the
desired output frequency band. The modulus of this divider stage is controlled dynamically by the output from the
- modulator. The tuning resolution is sufficient to tune to the commanded frequency with a maximum accuracy of
312.5 Hz anywhere in the range between 240–960 MHz.
5.1.1. VCO
The output of the VCO is automatically divided down to the correct output frequency depending on the hbsel and
fb[4:0] fields in "Register 75h. Frequency Band Select." The VCO integrates the resonator inductor, tuning varactor,
so no external VCO components are required.
The VCO uses a capacitance bank to cover the wide frequency range specified. The capacitance bank will
automatically be calibrated every time the synthesizer is enabled. In certain fast hopping applications this might not
be desirable so the VCO calibration may be skipped by setting the appropriate register.
5.2. Power Amplifier
The RFM42B contains an internal integrated power amplifier (PA) capable of transmitting at output levels between-1
and +20dBm. The RFM43B contains a PA which is capable of transmitting output levels between –8 to +13 dBm.
The PA can chang the output
efficiency will not be constant. The PA output is ramped up and down to prevent unwanted spectral splatter.
Tel: [phone]
Fref = 10 M
Fax: [phone]
power by adjusting txpow[2:0] will scale both the output power and current but the
PFD
Figure 10. PLL Synthesizer Block Diagram
CP
Modulation
TX
LPF
Sigma
Delta-
N
E-mail: [e-mail] http://www.hoperf.com
VCO
Selectable
Divider
choosing data rate, deviation,
to the loop in the digital
RFM42B/43B
TX
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