CMX469A 1200/2400/4800 Baud FFSK/MSK Modem D/469A/2 May 2001 Provisional Issue Features Applications • Full-Duplex FFSK/MSK Modem with Separate Rx and Tx Enable Functions • Data-Over Radio • Pin Selectable Data Rates: 1200, 2400 or 4800 Baud • Radio and General Applications • Pin Selectable Xtal/Clock Inputs: 1.008MHz or 4.032MHz • Two Way Radio (MPT1327) Signalling • Personal/Cordless Telephone • Narrowband Coax Data Channels • Portable Data Terminals • Clock Recovery Facility • Carrier Detect Facility • Low Power Operation (2.0mA typ. at 3.0V) 1.1 Brief Description The CMX469A is a single-chip CMOS LSI circuit which operates as a full-duplex 1200, 2400 or 4800 baud FFSK/MSK modem. The mark and space frequencies are 1200/1800, 1200/2400 and 2400/4800 Hz respectively. Tone frequencies are phase continuous; transitions occur at the zero crossing point. A common Xtal oscillator with a choice of two clock frequencies (1.008MHz or 4.032MHz) provides baud-rate, transmit frequencies, and Rx and Tx synchronization. The transmitter and receiver operate entirely independently, including the individual section powersave functions. The CMX469A includes on-chip circuitry for Carrier Detect and Rx Clock recovery, both of which are made available as output pins. Rx, Tx and Carrier Detect paths contain bandpass filters to optimise signal conditions in each section of the modem. The CMX469A demonstrates good sensitivity and bit-error-rate under adverse signal conditions. The Carrier Detect time constant is set by an external capacitor, so that the product's performance can be optimised in high noise environments. This low-power device operates from a single supply between 2.7V and 5.5V, requires few external components and is available in a wide variety of plastic packages. 2001 Consumer Microcircuits Limited 1200/2400/4800 Baud FFSK/MSK Modem CMX469A CONTENTS Page Section 1.0 Features and Applications.......................................................................2 1.1 Brief Description .......................................................................................2 1.2 Block Diagram ...........................................................................................4 1.3 Signal List...................................................................................................5 1.4 External Components ...............................................................................7 1.5 General Description ..................................................................................8 1.6 Application Notes......................................................................................9 1.7 Performance Specification.....................................................................10 1.7.1 Electrical Performance..............................................................10 1.7.2 Packaging....................................................................................16 2001 Consumer Microcircuits Limited 3 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem 1.2 CMX469A Block Diagram Figure 1 Block Diagram 2001 Consumer Microcircuits Limited 4 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem 1.3 CMX469A Signal List CMX469A D3 E2 P6 Signal Description Pin No. Pin No. Pin No. Name Type 1 1 1 CLOCK/XTAL I/P The input to the on-chip inverter, for use with either a 1.008MHz or a 4.032MHz Xtal or an external clock. Clock frequency selection is by means of the CLOCK RATE pin. This affects the operational data rate of the device. Operation of any CML microcircuit without a Xtal or clock input may cause device damage. 2 2 2 XTALN O/P The output of the on-chip inverter. 3 3 3 Tx SYNC O/P O/P A squarewave, produced on-chip, to synchronize the input of logic data and transmission of the FFSK/MSK signal. 4 5 5 Tx SIGNAL O/P O/P When the transmitter is enabled, this pin outputs the FFSK/MSK signal. With the transmitter disabled, this pin is set to a high-impedance state. 5 7 6 Tx DATA I/P I/P The serial logic data to be transmitted is input to this pin. 6 8 7 Tx ENABLEN I/P A logic ‘0’ will enable the transmitter. A logic ‘1’ at this input will put the transmitter into powersave whilst forcing Tx SYNC OUTPUT to a logic ‘1’ and Tx SIGNAL OUTPUT to a high-impedance state. This pin is internally pulled to VDD. 7 9 8 BANDPASS O/P O/P The output of the Rx Bandpass Filter. This output impedance is typically 10kΩ and may require buffering prior to use. 8 10 9 Rx ENABLE I/P The control of the Rx function 9 11 10 VBIAS BI The output of the on-chip analogue bias circuitry. Held internally at VDD/2, this pin should be decoupled to VSS by a capacitor (C2). This bias voltage is maintained under all powersave conditions. 10 12 11 VSS PWR 11 13 12 UNCLOCKED DATA O/P O/P The recovered asynchronous serial data output from the receiver. 12 14 13 CLOCKED DATA O/P O/P The recovered synchronous serial data output from the receiver. Data is latched out by the recovered clock, available at the Rx SYNC O/P. 2001 Consumer Microcircuits Limited 5 Negative supply rail (GND). D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem CMX469A CMX469A D3 E2 P6 Signal Description Pin No. Pin No. Pin No. Name Type 13 15 14 CARRIER DETECT O/P O/P When an FFSK/MSK signal is being received this output is a logic ‘1’. 14 16 15 Rx SIGNAL I/P I/P The FFSK/MSK signal input for the receiver. This input should be coupled via a capacitor, C3. 15 18 17 Rx SYNC O/P O/P A flywheel squarewave output. This clock will synchronize to incoming Rx FFSK/MSK data. 16 19 16 1200/2400 BAUD SELECT I/P A logic ‘1’ on this pin selects the 1200 baud option. Tone frequencies are: one cycle of 1200Hz represents a logic ‘1,’ one-and-a-half cycles of 1800Hz represents a logic ‘0.’ A logic ‘0’ on this pin selects the 2400 baud option. Tone frequencies are: one-half cycle of 1200Hz represents a logic ‘1,’ one cycle of 2400Hz represents a logic ‘0.’ This function is also used, in part, to select the 4800 baud option. This pin has an internal 1MΩ pullup resistor. 17 20 18 4800 BAUD SELECT I/P A logic ‘1’ on this pin combined with a logic ‘0’ on the 1200/2400 BAUD SELECT pin will select the 4800 baud option (1MΩ pulldown resistor). Tone frequencies are: one-half cycle of 2400Hz represents a logic ‘1,’ one cycle of 4800Hz represents a logic ‘0.’ Operation at 4800 baud is only achieved by using a 4.032MHz Xtal or clock. 18 21 19 CLOCK RATE I/P A logic input to select and allow the use of either a 1.008MHz or 4.032MHz Xtal/clock. Logic ‘1’ = 4.032MHz, logic ‘0’ = 1.008MHz. This input has an internal pulldown resistor (1.008MHz). 19 22 20 CARRIER DETECT TIME CONSTANT BI Part of the carrier detect integration function. The value of C4 connected to this pin will affect the carrier detect response time and hence noise performance. 20 24 22 VDD PWR Positive supply rail. A single 2.7 to 5.0 volt supply is required. This pin should be decoupled to VSS by a capacitor (C5). 4, 6, 17, 23 Notes: 4, 21 I/P = Input 2001 Consumer Microcircuits Limited No internal connection, do not use. O/P = Output 6 BI = Bidirectional PWR = Power D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem 1.4 CMX469A External Components Component Value R1 1.0MΩ C1 33.0pF C2 1.0µF C3 0.1µF C4 0.1µF C5 1.0µF C6 1.0µF C7 33.0pF X1 1.008MHz or 4.032MHz Notes: 1. VBIAS may be decoupled to VSS and VDD using C2 and C6 when input signals are referenced to the VBIAS pin. For input signals referenced to VSS, decouple VBIAS to VSS using C2 only. 2. The performance of the Carrier Detect function will be affected by the nature of the noise spectrum in the received channel. The value of C4 determines the Carrier Detect Time Constant. A long time constant results in improved noise immunity but increased response time. C4 may be varied to trade-off response time for noise immunity. 3. A 4.032MHz Xtal/clock is required for 4800 Baud operation. Figure 2 Recommended External Components 2001 Consumer Microcircuits Limited 7 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem 1.5 CMX469A General Description The CMX469A has two sections, apart from the Xtal oscillator circuit and clock dividers. These sections may be independently powersaved. Transmitter The transmitter is enabled by taking Tx EnableN low. Serial data applied to Tx Data Input is sampled internally and an FFSK/MSK sequence is generated. After filtering, this is output at Tx Signal O/P and the transmit clock derived from this signal is output at Tx Sync O/P. Receiver The receiver is enabled by taking Rx Enable high. The signal applied to Rx Signal I/P is filtered and recovered as serial data from the Unclocked Data O/P. A flywheel synchroniser is used to extract a clock from the recovered serial data stream. The clock is available at Rx Sync O/P and the retimed serial data is available at Clocked Data O/P. The integrated peak values of the Rx amplitude are compared with out-of-band noise levels and used to make a signal-to-noise assessment, which is available at Carrier Detect O/P. A Bandpass O/P is also available from the output of the first Rx filter stage, but will require buffering before use. 2001 Consumer Microcircuits Limited 8 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem 1.6 CMX469A Application Notes Rx Enable The control of the relevant outputs with reference to the Rx Enable input is described below: Rx Enable Rx Function Clock Data O/P Carrier Detect O/P Rx Sync Out ‘1’ Enabled Enabled Enabled Enabled ‘0’ Powersave ‘0’ ‘1’ or ‘0’ ‘1’ or ‘0’ After enabling the Receiver, a time of at least 8 bit periods plus 2ms should be allowed for the Carrier Detect circuit to stabilise and give a valid output. Operational Data Rate Configurations Operational Data Rate Configurations are as described below: Xtal/Clock Frequency 1.008MHz 4.032MHz Clock Rate ‘0’ ‘0’ ‘1’ ‘1’ ‘1’ 1200/2400 Select ‘1’ ‘0’ ‘1’ ‘0’ ‘0’ 4800 Select ‘0’ ‘0’ ‘0’ ‘0’ ‘1’ Baud Rate 1200 2400 1200 2400 4800 Test Set Up Figure 3 Suggested CMX469A Test Set-Up 2001 Consumer Microcircuits Limited 9 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem 1.7 Performance Specification 1.7.1 Electrical Performance CMX469A Absolute Maximum Ratings Exceeding these maximum ratings can result in damage to the device. Min. -0.3 -0.3 -30 -20 Max. 7.0 VDD + 0.3 +30 +20 Units V V mA mA D3 Package Total Allowable Power Dissipation at Tamb = 25°C ... Derating Storage Temperature Operating Temperature Min. Max. 800 13 +125 +85 Units mW mW/°C °C °C E2 Package Total Allowable Power Dissipation at Tamb = 25°C ... Derating Storage Temperature Operating Temperature Min. Max. 320 5.3 +125 +85 Units mW mW/°C °C °C P6 Package Total Allowable Power Dissipation at Tamb = 25°C ... Derating Storage Temperature Operating Temperature Min. Max. 800 13 +125 +85 Units mW mW/°C °C °C Supply (VDD - VSS) Voltage on any pin to VSS Current into or out of VDD and VSS pins Current into or out of any other pin 2001 Consumer Microcircuits Limited 10 -55 -40 -55 -40 -55 -40 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem CMX469A Operating Limits Correct operation of the device outside these limits is not implied. Notes Supply (VDD - VSS) Operating Temperature Xtal Frequency 1 Min. 2.7 -40 4.028 Max. 5.5 +85 4.036 Units V °C MHz Note 1: A Xtal frequency of 1.008MHz (1200/2400 baud only) or 4.032MHz is required for correct operation. A frequency tolerance of ±0.1% is recommended, but ultimately the tolerance selected will depend upon system requirements. Operating Characteristics For the following conditions unless otherwise specified: VDD = 2.7V at Tamb = 25°C and VDD = 3.0V to 5.5V at Tamb = −40°C to +85°C, Xtal/Clock Frequency = 4.032MHz, Bit Rate = 1200 baud, Rx Input Level = 300mVrms. Notes Min. Typ. Max. Units Static Values IDD Rx Enabled, Tx Disabled (VDD = 5.0V) (VDD = 5.0V) IDD Rx and Tx Enabled (VDD = 5.0V) IDD Rx and Tx Disabled 2 2 2 - 3.6 4.5 650 - mA mA µA IDD Rx Enabled, Tx Disabled (VDD = 3.0V) (VDD = 3.0V) IDD Rx and Tx Enabled (VDD = 3.0V) IDD Rx and Tx Disabled 2 2 2 - 1.5 2.0 300 - mA mA µA Logic ‘1’ Level Logic ‘0’ Level Digital Output Impedance Analogue and Digital Input Impedance Tx Output Impedance (VDD = 5.0V) 1 1 70% 100 - 4.0 0.6 30% 1.0 VDD VDD kΩ kΩ kΩ 3, 4 4, 5 100 230 1000 mVrms - 2.5 1.5 1.5 - 10-4 10-3 10-3 - <1.0 - 10-8 - 0.995 - Dynamic Values Receiver Signal Input Dynamic Range SNR = 50dB Bit Error Rate at SNR = 12dB 1200 Baud 2400 Baud 4800 Baud Bit Error Rate at SNR = 20dB 1200/2400/4800 Baud Receiver Synchronization at SNR = 12dB probability of bit 16 being correct 2001 Consumer Microcircuits Limited - 4, 5 7 11 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem CMX469A Carrier Detect Sensitivity Probabilty of CD being High after bit 16: with SNR = 12dB with 230mVrms Noise and No Signal Notes Min. Typ. Max. Units 3 1, 7, 8 - - 150 mVrms 9 9 Transmitter Output Tx Output Level Output Level Variation for 1200/1800Hz or 1200/2400Hz or 2400/4800Hz 1 Output Distortion 3rd Harmonic Distortion Isochronous Distortion 1200Hz - 1800Hz/1800Hz - 1200Hz 1200Hz - 2400Hz/2400Hz - 1200Hz 2400Hz - 4800Hz/4800Hz - 2400Hz 10 10 Logic ‘1’ Carrier Frequency 1200 Baud 2400 Baud 4800 Baud Logic ‘0’ Carrier Frequency 1200 Baud 2400 Baud 4800 Baud 6 6 6 6 6 6 0.995 0.05 - 775 - mVrms 0 - +/-1.0 dB - 3.0 2.0 5.0 3.0 % % - 25.0 20.0 10.0 40.0 30.0 20.0 µs µs µs - 1200 1200 2400 1800 2400 4800 - Hz Hz Hz Hz Hz Hz Notes: 1. Measured at V DD = 5.0 volts. Signal levels and thresholds are proportional to V DD. 2. Excludes any current drawn by external components, but includes current drawn by the crystal components. 3. See Figure 6 (Typical Variation of BER with Input Signal Level). 4. SNR = Signal-to-Noise Ratio in the Bit-Rate Bandwidth. 5. See Figure 7 (Typical Rx BER vs Signal-to-Noise Ratio). 6. Dependent upon Xtal tolerance. 7. With an alternating (1010...) pattern. 8. Measured with a 150mVrms input signal (no noise). 9. A signal level of 230mVrms is used in C.D. probability measurements. Noise bandwidth is 5kHz (1200/2400 baud operation) or 8kHz (4800 baud operation). See Section 1.4, Note 2 for details on optimising noise immunity. 10. For an unmodulated carrier. 2001 Consumer Microcircuits Limited 12 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem CMX469A Interface Timing Diagrams tESET Tx ENABLE Tx SYNC t DH t DSET Tx DATA DC = Don't DV = Data Valid Care DC t TDR DC DV DV DC tTDR DC DV t TxD 1200 BAUD Tx OUTPUT 2400 BAUD Tx OUTPUT OPEN CIRCUIT OPEN CIRCUIT OPEN CIRCUIT OPEN CIRCUIT TX DATA must be valid at the time of the rising edge of TX SYNC. Therefore the optimum time to change TX DATA is on the falling edge of TX SYNC. Figure 4 Transmitter Timing Rx SIGNAL I/P 2400/4800 BAUD LOGIC '0' LOGIC '1' Rx SIGNAL I/P 1200 BAUD t ID 1 Rx SYNC O/P (1200Hz) 0 Undetermined State t RDR 1 CLOCKED DATA O/P LOGIC '1' LOGIC '0' 0 The optimum time to sample the CLOCKED DATA O/P is on the falling edge of RX SYNC O/P. Figure 5 Receiver Timing 2001 Consumer Microcircuits Limited 13 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem 1.7.1 CMX469A Electrical Performance (continued) Interface Timings Notes Min. Typ. Max. Units tESET Tx Delay, Signal to Disable Time 2 2.0 - 800 µs tDSET Data Set-Up Time 1 2.0 - - µs tDH Data Hold Time 2.0 - - µs tTXD Tx Delay to O/P Time - 1.2 tTDR Tx Data Rate Period 2 - 833 - µs tRDR Rx Data Rate Period 2 800 - 865 µs Undetermined State (see Figure 5) - - 2.0 µs tID Internal Rx Delay - 1.5 - ms Notes: 1. Consider the Xtal/Clock tolerance. 2. 1200 Baud example. - µs 1 x 10 -1 * BIT RATE BANDWIDTH 1 x 10 -2 B 12 dB SN R* SN R * 02 Bd -3 * S RN ETA R R ORRE TI B 1 x 10 10 d 1 x 10 -4 1 x 10 -5 100 50 150 200 250 500 300 INPUT 700 800 SIGNAL LEVEL (mVrms) Figure 6 Typical Variation of Bit Error Rate with Input Level 2001 Consumer Microcircuits Limited 14 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem CMX469A Figure 7 Typical Rx Bit Error Rate vs Signal-to-Noise Ratio 2001 Consumer Microcircuits Limited 15 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem 1.7.2 CMX469A Packaging Figure 8 D3 Mechanical Outline: Order as part no. CMX469AD3 Figure 9 E2 Mechanical Outline: Order as part no. CMX469AE2 2001 Consumer Microcircuits Limited 16 D/469A/2 1200/2400/4800 Baud FFSK/MSK Modem CMX469A Figure 12 P6 Mechanical Outline: Order as part no. CMX469AP6 Handling precautions: This product includes input protection, however, precautions should be taken to prevent device damage from electro-static discharge. CML does not assume any responsibility for the use of any circuitry described. No IPR or circuit patent licences are implied. CML reserves the right at any time without notice to change the said circuitry and this product specification. CML has a policy of testing every product shipped using calibrated test equipment to ensure compliance with this product specification. Specific testing of all circuit parameters is not necessarily performed. Oval Park - LANGFORD MALDON - ESSEX CM9 6WG - ENGLAND Telephone: +44 (0)1621 875500 Telefax: +44 (0)1621 875600 e-mail: [email protected] http://www.cmlmicro.co.uk