CMX994/CMX994A/CMX994E /CMX994G Direct Conversion Receivers
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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 CMX994 - Standard and low power mode CMX994A - Standard and additional low power modes CMX994E - Enhanced, standard and low power modes CMX994G - Enhanced, 30MHz guaranteed performance  Rx single conversion to zero IF, near-zero IF or low IF; zero IF eliminates image responses  Very high mixer IIP2 for practical zero IF receiver  100MHz to 1GHz I/Q demodulator (CMX994A/E/G) 100MHz to 940MHz I/Q demodulator (CMX994) Extended operation down to 30MHz and up to 1.218GHz  LNA with gain control  Local Oscillator LO synthesiser VCO negative resistance amplifier Rx LO divide by 2, 4 or 6 modes Tx LO Output with divide by 1, 2, 4, or 6 modes Direct Conversion Receiver  Precise filtering with 1:2:4 bandwidth select control  3.0V – 3.6V Low power Operation  Small size 40-pin VQFN Package Analogue/digital multi-mode radio Software Defined Radio (SDR) Data telemetry modems Satellite communications Constant envelope and linear modulation Rx function compatible with CMX998 Cartesian Feedback Loop Transmitter  Narrowband e.g. 25kHz, 12.5kHz, 6.25kHz  Wideband Data e.g. >1MHz bandwidth Baseband Signal Processing C-BUS Reset Rx Enable Tx Enable 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 –40°C to +85°C and are available in a small 40pin 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.

Direct Conversion Receivers CONTENTS Section

Direct Conversion Receivers

Direct Conversion Receivers

Direct Conversion Receivers Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 Figure 28 Figure 29 Figure 30 Figure 31 Figure 32 Figure 33 Figure 34 Changes Section 9.1.3: I/Q demodulator maximum noise figure in Enhanced mode changed to 17 dB at 450 MHz. Section 9.1.3: I/Q demodulator gain changed to 52 dB (V/V). Section 9.1.3: Maximum I/Q amplitude balance changed from ±0.15dB to ±0.2dB. Section 9.2: Updated Q4 package diagram CMX994G version added with guaranteed performance down to 30MHz. Section 9.1.3 and 8.2 have been updated. Mixer operation extended to 1.218GHz:...

Direct Conversion Receivers Block Diagram Optional Bandpass Filter VCCRF VCCRXIF VCCLO VCCSYNTH RXEN TXEN RXQP RXQN C-BUS Control Interface CSN RDATA SCLK CDATA RESETN External Resonator and Varactors DVDD VDDIO Alternative Local Oscillator Reference Oscillator Figure 1 Block Diagram

Direct Conversion Receivers Pin Name IFLT2N IFLT1P IFLT1N VCCRXIF VCCLNA LNAIN LNAOUT VCCRF MIXIN TXLO VCCLO LOP LON VCOP1 VCOP2 VCON1 VCON2 VCCSYNTH FREF DO DGND TXEN RXEN CSN RDATA SCLK CDATA RESETN DVDD VDDIO RREF QFLT1N QFLT1P QFLT2N QFLT2P RXQP RXQN RXIP RXIN IFLT2P Pin Function I channel 2 filter capacitor negative st I channel 1 filter capacitor positive st I channel 1 filter capacitor negative Supply for baseband circuits Supply for LNA LNA input LNA output Supply for RF circuits Rx mixer input LO output for Tx Supply for LO sections PLL LO positive input PLL LO negative input PLL...

Direct Conversion Receivers Input Output Bidirectional 3-state Output No Connection Power Signal Definitions Signal Name Vmax AVDD DVDD VDDIO DVSS (GND) AVSS (GND) Pins VCCRF, VCCRXIF, VCCSYNTH, VCCLO VCCLNA (see note) DVDD VDDIO DGND AGND Usage The maximum value of the supplies DVDD and AVDD Power supply for analogue circuits Power supply for digital circuits Power supply voltage for digital interface (C-BUS) Ground for digital circuits Ground for analogue circuits Table 1 Definition of Power Supply and Reference Voltages Note: The LNA has a separate power connection pin to provide...

Direct Conversion Receivers External Components Power Supply and Decoupling The CMX994/CMX994A/CMX994E/CMX994G have separate supply pins for the analogue and digital circuitry; a 3.3V nominal supply is recommended for all circuits but the data interface can run at a lower voltage than the rest of the device by setting the VDDIO supply to the required interface voltage. R7 VCCLO VCCSYNTH Figure 2 Recommended Power Supply Connections and Decoupling Table 2 Decoupling Components Notes: 1. Maximum Tolerances: Resistors 5%, capacitors 20%. 2. It is expected that any low-frequency interference...

Direct Conversion Receivers LNA The following sections show plots and tables of the LNA input (S 11) and output (S22) impedance. Separate data is shown for the 50 and 100 output modes which are selected by LNAZO bit in the Rx Gain Register (b3, $16; see section 7.7.1). Note that at low frequencies capacitive loads on the LNA output are not recommended, a high-pass matching network is preferred.