SI4460-C2A-GM Datasheet, PDF (36/53 Pages) Silicon Laboratories – HIGH-PERFORMANCE, LOW-CURRENT TRANSCEIVER

Si4463/61/60-C
TX Power vs Temp
20.5
20
19.5
19
18.5
18
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80
Temperature (C)
Figure 12. +20 dBm TX Power vs. Temp
5.5. Crystal Oscillator
The Si446x 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 30 MHz, but the circuit is
designed to handle any XTAL from 25 to 32 MHz. If a crystal different than 30 MHz is used, the POWER_UP API
boot command must be modified. The WDS calculator crystal frequency field must also be changed to reflect the
frequency being used. 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 the GLOBAL_XO_TUNE API property. The total internal capacitance is
11 pF and is adjustable in 127 steps (70 fF/step). The crystal frequency adjustment can be used to compensate for
crystal production tolerances. The frequency offset characteristics of the capacitor bank are demonstrated in
Figure 13.
Figure 13. Capacitor Bank Frequency Offset Characteristics
36
Rev 1.0