There appears to be a dead-zone between the Si4133 RF1 VCOs normal and extended tuning ranges. What is the effect of operating the RF1 VCO in this range?
The Si4133 RF1 VCO datasheet limits are 900-1806 MHz and 1850-2050 MHz for the normal and extended frequency operations respectively. Operation in the 1806-1850 MHz range is possible. However, this range falls outside the guaranteed datasheet specifications.
The device should be used in the extended frequency mode. Also, only the MLP package should be used. The extended frequency operation is implemented by setting the D1 bit of the main configuration register to 1 and setting VDD to between 3.0 and 3.6V. For more details, refer to Application Note 41 Extended Frequency Operation of Silicon Laboratories Radio Frequency Synthesizers and Application Note 31 Inductor Design for the Si41xx Synthesizer Family.
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