SX1231
ADVANCED COMMUNICATIONS & SENSING
DATASHEET
7. Application Information
7.1. Crystal Resonator Specification
Table 29 shows the crystal resonator specification for the crystal reference oscillator circuit of the SX1231. This
specification covers the full range of operation of the SX1231 and is employed in the reference design.
Table 29 Crystal Specification
Symbol Description
Conditions
Min
Typ
Max
Unit
FXOSC
XTAL Frequency
26
-
32
MHz
RS
XTAL Serial Resistance
XTAL Shunt Capacitance
External Foot Capacitance
-
-
30
2.8
16
140
7
ohms
pF
C0
CLOAD
On each pin XTA and XTB
8
22
pF
Notes - the initial frequency tolerance, temperature stability and ageing performance should be chosen in accordance
with the target operating temperature range and the receiver bandwidth selected.
- the loading capacitance should be applied externally, and adapted to the actual Cload specification of the XTAL.
- A minimum XTAL frequency of 28 MHz is required to cover the 863-870 MHz band, 29 MHz for the 902-928 MHz
band
7.2. Reset of the Chip
A power-on reset of the SX1231 is triggered at power up. Additionally, a manual reset can be issued by controlling pin 6.
7.2.1. POR
If the application requires the disconnection of VDD from the SX1231, despite of the extremely low Sleep Mode current, the
user should wait for 10 ms from of the end of the POR cycle before commencing communications over the SPI bus. Pin 6
(Reset) should be left floating during the POR sequence.
VDD
Pin 6
Undefined
(output)
Wait for
10 ms
Chip is ready from
this point on
Figure 36. POR Timing Diagram
Please note that any CLKOUT activity can also be used to detect that the chip is ready.
Rev 2 - Nov 2009
Page 73
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