Silicon Laboratories SI4421 manual Si4421 RX-TXALIGNMENT PROCEDURES

Page 33

Si4421

Si4421

RX-TX ALIGNMENT PROCEDURES

RX-TX frequency offset can be caused only by the differences in the actual reference frequency. To minimize these errors it is suggested to use the same crystal type and the same PCB layout for the crystal placement on the RX and TX PCBs.

To verify the possible RX-TX offset it is suggested to measure the CLK output of both chips with a high level of accuracy. Do not measure the output at the XTL pin since the measurement process itself will change the reference frequency. Since the carrier frequencies are derived from the reference frequency, having identical reference frequencies and nominal frequency settings at the TX and RX side there should be no offset if the CLK signals have identical frequencies.

It is possible to monitor the actual RX-TX offset using the AFC status report included in the status byte of the receiver. By reading out the status byte from the receiver, the actual measured offset frequency will be reported. In order to get accurate values the AFC has to be disabled during the read by clearing the en bit in the AFC Control Command (page 21).

33

Image 33

Contents FEATURES FUNCTIONAL BLOCK DIAGRAMDESCRIPTION TYPICAL APPLICATIONSRF Power Amplifier PA DETAILED FEATURE-LEVELDESCRIPTIONData Filtering and Clock Recovery Si4421Wake-UpTimer Low Battery Voltage DetectorData Validity Blocks Crystal OscillatorName Si4421 PACKAGE PIN DEFINITIONSType FunctionInternal Pin Connections Si4421Name Internal connectionPIN10 Logic Diagram nRES I/O PIN6 Logic Diagram FSK / DATA / nFFSNote These pins can be left floating Si4421Typical Application Si4421Recommended supply decoupling capacitor values Pin Function vs. Operation ModeSi4421 GENERAL DEVICE SPECIFICATIONS Absolute Maximum Ratings non-operatingRecommended Operating Range ELECTRICAL SPECIFICATION DC CharacteristicsSi4421 AC Characteristics PLL parameters AC Characteristics ReceiverSi4421 AC Characteristics Transmitter Si4421AC Characteristics Turn-on/Turnaroundtimings AC Characteristics OthersNote 10 By design Si4421Si4421 CONTROL INTERFACE Timing SpecificationTiming Diagram Control Commands Control Register Default ValuesSi4421 Configuration Setting Command Description of the Control Commands2. Power Management Command Si4421Si4421 Logic connections between power control bits4. Data Rate Command Frequency Setting Command5. Receiver Control Command Si4421Si4421 VDI Logic DiagramSi4421 6. Data Filter CommandSi4421 7.FIFO and Reset Mode Command9. Receiver FIFO Read Command 8. Synchron Pattern Command10. AFC Command Si4421Bit 5-4rl1 to rl0 Si442111. TX Configuration Control Command Frequency Setting CommandSi4421 13. Transmitter Register Write Command 12. PLL Setting CommandSi4421 14. Wake-UpTimer Command 15.Low Duty-CycleCommandSi4421 Si4421 Vlb= 2.25 + V · 0.1 V Clock divider configuration17. Status Read Command Si4421Bit Name Si4421 INTERRUPT HANDLING Si4421 TX REGISTER BUFFERED DATA TRANSMISSION Typical TX register usage Si4421RECOMMENDED PACKET STRUCTURES Si4421 RX FIFO BUFFERED DATA READBit Rate 2.4 kbps Si4421 CRYSTAL SELECTION GUIDELINESBit Rate 9.6 kbps Bit Rate 38.4 kbpsSi4421 RX-TXALIGNMENT PROCEDURES Si4421 RESET MODES FIFO and Reset Mode Command page Sensitive Reset Enabled, Ripple on VddSW Reset Command Si4421Channel Selectivity and Blocking Si4421 TYPICAL PERFORMANCE CHARACTERISTICSSi4421 BER Curves in 433 MHz BandBER Curves in 868 MHz Band 434 MHz Si4421Schematics Si4421 REFERENCE DESIGNSEvaluation Board with 50 Ohm Matching Network Frequency Dependent Component ValuesPCB Layout Top View Bottom View Si4421Si4421 SchematicsEvaluation Board with Resonant PCB Antenna BIFA Frequency Dependent Component ValuesSi4421 PCB Layout Antenna designed for 868/915 MHz bandTop View Bottom View Si4421 PACKAGE INFORMATION 16-pinTSSOPSee Detail “A” Section B-B Si4421 Universal ISM Band FSK Transceiver RELATED PRODUCTS AND DOCUMENTSDemo Boards and Development Kits Related ResourcesSi4421