RFM24W Datasheet, PDF (27/34 Pages) List of Unclassifed Manufacturers – ISM Transceiver module

RFM24W
5.3.1.1. EZ Frequency Programming
5.3.1.2. Fast Frequency Hopping
5.4. Transmitter (TX)
The RFM24W is designed to supply +10dBm output power for less than 20mA for applications which require
operation from a single coin cell battery. The RFM24W can also operate with either class-E or switched current
matching. All PA options are single-ended to allow for easy antenna matching and low BOM cost. Automatic
ramp-up and ramp-down is automatically performed to reduce unwanted spectral spreading.
5.5. Crystal Oscillator
The RFM24W includes an integrated crystal oscillator with a fast start-up time of less than 250 μs. The design
is differential with the required crystal load capacitance integrated on-chip to minimize the number of external
components. By default, all that is required off-chip is the crystal. The default crystal is 30MHz but the circuit is
designed to handle any XTAL from 25 to 32 MHz. If a crystal different than 30MHz is used the
“GLOBAL_CLK_XTAL_ADJUST” API property must be modified. The crystal load capacitance can be digitally
programmed to accommodate crystals with various load capacitance requirements and to adjust the frequency of
the crystal oscillator. The tuning of the crystal load capacitance is programmed through “XXX” API property. The
total internal capacitance is 12.7 pF and is adjustable in 127 steps (100 fF/step). The crystal frequency adjustment
can be used to compensate for crystal production tolerances. Utilizing the on-chip temperature sensor and suitable
control software, the temperature dependency of the crystal can be canceled.
A TCXO or external signal source can easily be used in lieu of a conventional XTAL and should be connected to
the XIN pin. The incoming signal is ac coupled internally to a squaring buffer so no external ac coupling or dc bias
is required. If dc is provide it should be set to 500 mV. The incoming signal amplitude is should be set in the range
from 500–900 mV. The internal capacitor bank will create a capacitive divider when an external source is used so
the XTAL capacitor bank should be set to 0.
28
Tel: [phone] Fax: [phone] E-mail: [e-mail] http:/ / www.hoperf.com