MICRF114 Datasheet, PDF (10/34 Pages) Microchip Technology – Low-Power Integrated Sub-GHz Wireless RF Transmitter

MICRF114
Select the transmit frequency parameter to ensure that
the actual operating frequency, which is determined by
the selected crystal, falls into the frequency range
defined by the parameter. Refer to Table 2-2.
TABLE 2-2: FREQUENCY RANGE
fTX range (MHz)
Min
Max
F<2:0>
285
305
0
305
325
1
325
345
2
345
365
3
365
385
4
385
405
5
405
425
6
425
445
7
Equation 2-1 through Equation 2-1 show that the rest
of the programmable parameters can be calculated
from the Control bit fields.
EQUATION 2-1: CRYSTAL LOAD
CAPACITOR
Crystal Load Capacitor:
CXT = 7 pF + X <4:0> * 0.5 pF
EQUATION 2-2: RF TRANSMIT POWER
RF Transmit Power:
PTX = -2 dBm + P <3:0> dBm
EQUATION 2-3: RF OUTPUT TUNING
CAPACITOR
RF Output Tuning Capacitor:
CTX = 0 pF + R <3:0> * 0.2 pF
The operating frequency, the crystal load capacitor,
and the RF output tuning capacitor settings depend on
the selection of external components and, to a lesser
extent, PCB layout. If these parameters are different
from the default values, it must be set only once during
the first transmission after a POR event.
2.5 Transmitting
The MICRF114 is normally in Sleep mode. The MCU
always initiates entry into Transmit mode by sending a
Start bit, the compulsory Control bits, and the optional
Configuration bits to the MICRF114, which starts its
wake-up sequence. After the wake-up delay, it
transmits the data present on its SDI pin. The MCU
holds the SDI pin low for the maximum specified wake-
up time. If calibration is requested, the maximum
specified calibration time must be added to the wake-
up time.
Transmit parameters are not usually changed on the
fly, and recalibration is not necessary. Therefore, the
MCU can use the quick-start transmit sequence as
described in Section 2.3 “Communication with the
MCU”. However, except in the rare case that all default
parameter settings are acceptable for the application,
the first transmission after a POR event must include
sending the required Configuration bits. Recalibration
is always needed when the transmit frequency is in a
band that is different from the default value.
The MICRF114 stays in Transmit mode until the MCU
sends a Stop bit and then reverts to Sleep mode
without any time-out delay.
DS50002416A-page 10
Preliminary
 2015 Microchip Technology Inc.