CMX994/CMX994A/CMX994E /CMX994G Direct Conversion Receivers CMX994 / CMX994A (lower power options) / CMX994E (enhanced performance) / CMX994G (enhanced performance) D/994 994A 994E 994G/7 November 2020 DATASHEET Provisional Features Direct conversion receiver family Precise filtering with 1:2:4 bandwidth CMX994 - Standard and low power mode select control CMX994A - Standard and additional low power modes 3.0V 3.6V Low power Operation CMX994E - Enhanced, standard and low power modes Small size 40-pin VQFN Package CMX994G - Enhanced, 30MHz guaranteed performance Rx single conversion to zero IF, near-zero IF or low IF zero Applications IF eliminates image responses Very high mixer IIP2 for practical zero IF receiver Analogue/digital multi-mode radio 100MHz to 1GHz I/Q demodulator (CMX994A/E/G) Software Defined Radio (SDR) 100MHz to 940MHz I/Q demodulator (CMX994) Data telemetry modems Extended operation down to 30MHz and up to 1.218GHz Satellite communications LNA with gain control Constant envelope and linear modulation Local Oscillator Rx function compatible with CMX998 LO synthesiser Cartesian Feedback Loop Transmitter VCO negative resistance amplifier Narrowband e.g. 25kHz, 12.5kHz, 6.25kHz Rx LO divide by 2, 4 or 6 modes Wideband Data e.g. >1MHz bandwidth Tx LO Output with divide by 1, 2, 4, or 6 modes Baseband I/Q Signals Signal Processing CMX994 CMX994A C-BUS T/R CMX994E Reset CMX994G Ref. Osc. Rx Enable Direct Conversion Receiver C Flash Tx LO Tx Enable 1 Brief Description The CMX994/CMX994A/CMX994E/CMX994G is a family of direct conversion receiver ICs with PowerTrade, the ability to dynamically select power vs. performance modes to optimise operating trade-offs. All four devices include a broadband LNA with gain control followed by a high dynamic range, very high IIP2, I/Q demodulator. The receiver baseband section includes amplifiers and precise, configurable bandwidth, baseband filter stages. LO generation is provided by an integer-N PLL and a VCO negative resistance amplifier an external LO may also be used. LO dividers are provided for flexible multi-band operation. The devices operate from a single 3.3V supply over a temperature range of 40C to +85C and are available in a small 40- pin VQFN (Q4) package. Relative to the CMX994 the CMX994A enables a significant reduction in power by allowing LO phase correction to be turned off. A further reduction is possible by disabling either the I or Q channel in a channel monitoring mode. The CMX994E includes all the features of the CMX994A and adds an enhanced performance mode for improved intermodulation in the receive mixers. The CMX994G has been introduced for radios operating down to 30MHz with guaranteed down-converter performance. Throughout this datasheet, descriptions and features for the CMX994E also apply to the CMX994G, unless otherwise stated. 2020 CML Microsystems Plc D/994 A E G/7 Direct Conversion Receivers CMX994/CMX994A/CMX994E/CMX994G CONTENTS Section Page 1 Brief Description ...................................................................................................................................... 1 2 History ..................................................................................................................................................... 5 3 Block Diagram .......................................................................................................................................... 6 4 Pin and Signal List .................................................................................................................................... 7 4.1 Signal Definitions ............................................................................................................................................ 8 4.2 Connection of Unused Pins ............................................................................................................................ 8 5 External Components ............................................................................................................................... 9 5.1 Power Supply and Decoupling ........................................................................................................................ 9 5.2 Receiver ........................................................................................................................................................ 10 5.2.1 LNA ............................................................................................................................................................... 10 5.2.2 Mixers and Baseband Section ...................................................................................................................... 13 5.3 Local Oscillator ............................................................................................................................................. 15 5.3.1 Local Oscillator Input .................................................................................................................................... 15 5.3.2 VCO and PLL ................................................................................................................................................. 15 5.4 RESETN ......................................................................................................................................................... 17 6 General Description ............................................................................................................................... 18 6.1 General Operation ........................................................................................................................................ 19 6.1.1 Rx/Tx Enable ................................................................................................................................................. 19 6.2 Receiver Operation ....................................................................................................................................... 19 6.2.1 DC Offset Correction .................................................................................................................................... 19 6.2.2 Receiver Filters and Bandwidth Options ...................................................................................................... 20 6.2.3 Baseband Filter Design and Required Correction......................................................................................... 21 6.2.4 Operation at Wider Bandwidths................................................................................................................... 22 6.3 Local Oscillator Operation ............................................................................................................................ 22 6.3.1 PLL ................................................................................................................................................................ 23 6.3.2 PLL Enable..................................................................................................................................................... 24 7 C-BUS Interface and Register Descriptions ............................................................................................. 25 7.1 General Reset: 10 (no data)........................................................................................................................ 26 7.2 General Control Register .............................................................................................................................. 27 7.2.1 General Control: 11 - 8-bit write only ........................................................................................................ 27 7.2.2 General Control: E1 - 8-bit read only .......................................................................................................... 27 7.3 Rx Control Register ....................................................................................................................................... 28 7.3.1 Rx Control: 12 8-bit write only ................................................................................................................ 28 7.3.2 Rx Control: E2 8-bit read only .................................................................................................................. 28 7.4 Rx Offset Register ......................................................................................................................................... 29 7.4.1 Rx Offset: 13 8-bit write only ................................................................................................................... 29 7.4.2 Rx Offset: E3 - 8-bit Read only .................................................................................................................... 29 7.5 LNA Intermodulation Control Register ......................................................................................................... 30 7.5.1 LNA IM Control: 14 8-bit write only ......................................................................................................... 30 7.5.2 LNA IM Control: E4 8-bit read only .......................................................................................................... 30 7.6 Options Control Register CMX994A and CMX994E only ........................................................................... 31 7.6.1 Options Control: 15 8-bit write only ........................................................................................................ 31 7.6.2 Options Control: E5 8-bit read only ......................................................................................................... 31 7.7 Rx Gain Register ........................................................................................................................................... 32 7.7.1 Rx Gain: 16 8-bit write only ..................................................................................................................... 32 7.7.2 Rx Gain: E6 8-bit read only ...................................................................................................................... 32 7.8 Extended Rx Offset Register CMX994A and CMX994E only ...................................................................... 33 2020 CML Microsystems Plc D/994 A E G/7 Page 2