AMIS-53000 Datasheet, PDF (40/99 Pages) AMI SEMICONDUCTOR – Frequency Agile Transceiver

AMIS-53000 Frequency Agile Transceiver
Data Sheet
Figure 33: EE Flow Diagram
6.4 Frequency
The AMIS-53000 uses an internal PLL/VCO to generate the RF frequencies for both transmit and receive. Only one set of registers
needs to be programmed to generate the TX frequency and to generate the LO frequency to produce the mixing frequency for
converting the received signal to the low IF (about 500kHz). The AMIS-53000 can do a self-calibration, which will trim internal
capacitance to tune the TX and RX frequencies. The AMIS-53000 needs to run the self-calibration (must be started by the external
host/controller) at least once between startup and entering a command such as TX, RX, Sniff, etc.
6.4.1. Frequency Control
AMIS has developed an executable program (AMIS-53CALC.exe, available from AMIS, which generates the register values for the
frequency divider and fractional word to produce a given frequency. First, the AMIS-53000 must have the correct LC for the desired
frequency connected to the VCO pins. There is internal capacitance that is part of the capacitance for determining the value of the
inductor. The following equation can be used to determine the approximate value of the LC components. Remember that the VCO is
sensitive to the placement of the LC components - they should be placed as close to the AMIS-53000 as practical (even short traces
add significant parasitics) and the traces to the components should be made symmetrical.
Where: Ltot and Ctot are the total inductance and capacitance respectively at the VCO pins. This includes the internal capacitance of
approximately 2pF.
The RF PLL is a 24-bit Sigma Delta based fractional N synthesizer used to provide the LO signal for receive, and a direct RF output for
transmit.
AMI Semiconductor – Aug. 05, Rev. 1.0
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