CMX940 High Performance RF Synthesizer Low-power, Frac-N RF Synth with Highly-configurable, Near-noiseless Clock Multiplier Technology D/940/5 December 2021 Advance 16- and 24-bit fractional-N PLL modes Features RF output frequency 49 - 2040 MHz High comparison frequency 120 MHz Low current consumption Very fast frequency switching <50 s Supply voltage 3.0 - 3.6 V Compatible with EN 300 113, EN 300 086 Low 1 Hz normalised PLL noise floor -225 dBc/Hz Phase noise -123 dBc/Hz, 25 kHz offset at 435 MHz Applications Dual programmable RF outputs PMR / LMR Low noise VCO -142 dBc/Hz, 1 MHz offset at 435 MHz Wireless Data Modem Low level of spurious products General Purpose RF and IF Automatic VCO selection and calibration Marine Radio 1 Brief Description The CMX940 is a low-power high performance Frac-N PLL with fully integrated wideband VCO and programmable output divider, generating RF signals over a continuous frequency range of 49 MHz to 2040 MHz. It has two single-ended RF outputs to support Tx and Rx sub-systems. A configurable reference path can be used to minimise close-in phase noise and mitigate integer and fractional boundary spurious. The IC is configured by an SPI compatible C-BUS serial bus. Available in a 48-pin 7x7 mm LGA package, CMX940 is highly integrated to reduce component count and PCB board area, requiring only loop filter and clock reference to provide a complete and very compact RF synthesizer solution. Low operating voltage and low power consumption make it the perfect choice for a wide variety of portable and battery powered wireless applications, including digital narrowband two-way radio equipment compliant with ETSI standards. 2021 CML Microsystems Plc High Performance RF Synthesizer CMX940 CONTENTS Section Page 1 Brief Description .................................................................................................. 1 2 Block Diagram ...................................................................................................... 7 3 Pin and Signal List ............................................................................................... 8 3.1 Signal Definitions ........................................................................................... 11 4 External Components ........................................................................................ 12 4.1 Power Supply and Decoupling ...................................................................... 12 4.2 C-BUS Interface for 1.8 V Control Signals .................................................... 13 4.3 RF System ..................................................................................................... 14 5 General Description ........................................................................................... 16 5.1 Overview ........................................................................................................ 16 5.2 Device Reset ................................................................................................. 16 5.3 Main Clocks ................................................................................................... 16 5.4 Reference PLL ............................................................................................... 17 5.5 Synthesizer PLL ............................................................................................. 18 5.6 Synthesizer Output Divider and Buffers ........................................................ 19 6 Registers ............................................................................................................. 20 6.1 Reference System Control ............................................................................ 22 6.1.1 REF GCR ( 75) ...................................................................................... 22 6.1.2 REF MCLK FREQ ( 76) ........................................................................ 22 6.1.3 REF ISE ( 77) ........................................................................................ 23 6.1.4 REF ISM ( 78) ....................................................................................... 23 6.1.5 REF GEN RST ( 79) ............................................................................. 23 6.1.6 REF DEVICE STATUS RD ( 83) ......................................................... 23 6.1.7 REF GCR RD ( C5) .............................................................................. 24 6.1.8 REF MCLK FREQ RD ( C6) ................................................................ 24 6.1.9 REF ISE RD ( C7) ................................................................................ 24 6.1.10 REF ISM RD ( C8) ............................................................................... 24 6.1.11 REF ISR RD ( C9) ................................................................................ 24 6.2 Reference PLL ............................................................................................... 24 6.2.1 REF PLL MDIV ( 7A) ............................................................................ 24 6.2.2 REF PLL MDIV RD ( CA) .................................................................... 24 6.3 Reference Calibration .................................................................................... 25 6.3.1 REF RVCO BIAS CAL ( 09) ................................................................ 25 6.3.2 REF RVCO FREQ CAL ( 0B) .............................................................. 25 6.3.3 REF RVCO AMP CAL ( 2C) ................................................................ 25 6.3.4 REF RVCO BIAS CAL RD ( D9) ........................................................ 25 6.3.5 REF RVCO FREQ CAL RD ( DB) ...................................................... 26 6.3.6 REF RVCO AMP CAL RD ( D6) ........................................................ 26 6.4 Reference LO Divider and Buffer .................................................................. 26 6.4.1 REF LO DIV ( 7B) ................................................................................ 26 6.4.2 REF LO BUF ( 7C) ............................................................................... 26 6.4.3 REF LO DIV RD ( CB) ......................................................................... 27 6.4.4 REF LO BUF RD ( CC) ....................................................................... 27 6.5 Reference MCLK Divider ............................................................................... 27 6.5.1 REF MCLK DIV ( 7D) ........................................................................... 27 6.5.2 REF MCLK DIV RD ( CD) ................................................................... 27 6.6 Synthesizer System Control .......................................................................... 28 6.6.1 SYN GCR ( 2E) ..................................................................................... 28 2021 CML Microsystems Plc 2