MRF39RA Datasheet, PDF (56/72 Pages) Microchip Technology – Low-Power, Integrated UHF Receiver

MRF39RA
6.0 APPLICATION INFORMATION
6.1 Crystal Resonator Specification
Table 6-1 shows the crystal resonator specification for
the crystal reference oscillator circuit of the MRF39RA.
This specification covers the full range of operation of
the MRF39RA and is employed in the reference
design.
TABLE 6-1: CRYSTAL SPECIFICATION
Symbol
FXOSC
RS
C0
CLOAD
Description
XTAL Frequency
XTAL Serial Resistance
XTAL Shunt Capacitance
External Foot Capacitance
Conditions
—
—
—
On each pin XTA and XTB
Min.
26
—
—
8
Note 1: The initial frequency tolerance,
temperature stability and aging
performance must be chosen in
accordance with the target operating
temperature range and the receiver
bandwidth selected.
2: The loading capacitance must be applied
externally and adapted to the actual
CLOAD specification of the XTAL.
3: A minimum XTAL frequency of 28 MHz is
required to cover the 863-870 MHz band,
29 MHz for the 902-928 MHz band.
6.2 Reset of the Chip
A Power-on Reset of the MRF39RA is triggered at
power-up. Additionally, a manual Reset can be issued
by controlling pin 6.
6.2.1 POR
If the application requires the disconnection of VDD
from the MRF39RA, despite the extremely low Sleep
mode current, the user must wait for 10 ms from the
end of the POR cycle before commencing
communications over the SPI bus. Pin 6 (RESET) must
be left floating during the POR sequence.
FIGURE 6-1:
POR TIMING DIAGRAM
VDD
Pin 6
(output)
Und efine d
Wait for _{Chip is ready from}
10 ms this point on
Note that any CLKOUT activity is also used to detect
that the chip is ready.
Typ.
Max. Unit
—
32 MHz
30
140 Ohms
2.8
7 pF
16
22 pF
DS40001778B-page 56
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