DATA BULLETIN MX439 MSK Modem Document #2048-0041.005 June 1995 Features Applications • 1200 Baud MSK Modem • Mobile & Cellular Radio Data Signaling • Meets Cellular & Trunked Radio Specifications • Personal Radio • Portable Data Terminals • Full-Duplex 1200 Baud • General Purpose Applications • On-Chip RX and TX Bandpass Filters • Clock Recovery and Carrier Detect • Pin Selectable Xtal/Clock Frequencies AVAILABLE PACKAGES MX439LH 24-pin PLCC MX439DW 24-pin SOIC MX439J: 22 pin CDIP MX439P: 22 pin PDIP Figure 1 - Internal Block Diagram Brief Description The MX439 is a single-chip CMOS LSI circuit which operates as a 1200 baud MSK modem. The mark and space frequencies are 1200Hz and 1800Hz phase continuous, and the frequency transitions occur at the zero crossing point. The transmitter and receiver will work independently, thus providing full-duplex operation at 1200 baud. The baud rate, transmit mark and space frequencies, and the TX and RX synchronization are all derived from a highly stable Xtal oscillator. The on-chip oscillator is capable of working at one of two input frequencies: 1.008MHz or 4.032MHz external Xtal/clock input. Frequency is pin-selectable with the “Clock Rate” logic input. The device includes circuitry for carrier detect and facility for the RX clock recovery. An on-board switched capacitor 900Hz - 2100Hz bandpass filter provides optimum carrier filtering. The use of switched capacitor analog filters and digital signal processing results in excellent dynamic performance with few external components; the CMOS process and current-saving techniques offer low standby supply current for portable battery-powered applications. MX439P package discontinued Pin Number Function DW J,P LH 1 1 1 Xtal/Clock: The input to an on-chip inverter for use with either a 1.008MHz or a 4.032MHz Xtal. Alternatively, an external clock may be used. Xtal frequency is selectable on the “Clock Rate” input pin. 2 2 2 Xtal: Output of the on-chip inverter. (See Figure 2.) 3 3 3 TX Sync O/P: MSK signal centered at a DC level of VBIAS - 0.7V. (See Figure 5.) 5 5 5 TX Signal O/P: With the transmitter disabled, this pin is set to a high impedance state. When the transmitter is enabled, this pin outputs the 1200/1800Hz MSK signal centered at a DC level of VBIAS - 0.7 V. (See Figure 5.) 7 6 7 TX Data I/P: Serial logic data to be transmitted is input to this pin and synchronized by the “TX Sync O/P.” (See Figure 5.) 8 7 8 TX Enable: A logic “1” applied to this input will put the transmitter into powersave while forcing “TX Sync O/P” to a logic “1” and “TX Signal O/P” to a high impedance state. A logic “0” will enable the transmitter (See Figure 5). This pin is internally pulled to VDD. 9 8 9 Bandpass O/P: This is the output of the RX 900Hz-2100Hz bandpass filter. The output impedance of this pin is typically 10kW and may require buffering prior to use. 10 9 10 RX Enable: This is the control of the RX function. The state of other outputs is given below: RX Enable “1” “0” RX Function Enabled Powersave Clock Data O/P Enabled “0” Carrier Detect Enabled “0” RX Sync Out Enabled “1” or “0” When both TX and RX functions are disabled, the bias voltage is switched internally to VSS and Bias pin output impedance is approximately 12.5kW. When the Bias pin is decoupled by a 1.0mF capacitor (C2) the MX439 may require up to 25ms to establish correct operation after enabling the RX function. This period may be decreased by either reducing the value of C2, lowering the Bias pin impedance externally, or adopting a different powersaving strategy (such as using C2 and C5 and supplying VDD via a series switch). This pin is internally pulled to VDD. 11 10 11 Bias: Provides bias internally and should be decoupled externally to Vss by capacitor (C2). (See Fig. 2.) 12 11 12 Vss: Negative supply rail (GND). 13 12 13 Unclocked Data O/P: This pin outputs recovered asynchronous serial data from the receiver. 14 13 14 Clocked Data O/P: This pin outputs recovered synchronous serial data from the receiver and is internally latched out by a recovered clock appearing on the “RX Sync O/P” pin. (See Figure 6.) 15 14 15 Carrier Detect O/P: This pin will output a logic “1” when an MSK signal is being received. 16 15 16 RX Signal I/P: This is the MSK signal input for the receiver. It should be decoupled using capacitor C3. 18 17 18 RX Sync O/P: This is a flywheel 1200Hz squarewave output which, upon presentation of the MSK data signal, is synchronized internally to the incoming data. (See Figure 6.) Page 2 MX439P MX439package discontinued MX-COM, Inc./Doc.#2048-0041.005 Pin Number Function DW J,P LH 21 19 21 Clock Rate: This logic input selects and allows the use of either a 1.008MHz or 4.032MHz Xtal/clock input to the on-chip inverter. Logic “1” = 4.032MHz; logic “0” = 1.008MHz. This input has an internal pulldown resistor (1.008MHz). 22 20 22 Carrier Detect Time Constant (t): This input forms 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. (See Figure 2, Note 3.) 24 22 24 VDD: Positive supply rail. A single 5 volt supply is required. 4,6,17 4,16, 19,20 18,21 23 4,6,17 19,20, 23 ) ) No Connection. ) Note: Output Loading. Large capacitive loads could cause the output pins of this device to oscillate. If capacitive loads in excess of 200pF are unavoidable, a resistor of (typically) 100W put in series with the load should minimize this effect. Component References Component R1 C1 C2 C3 C4 C5 C6 C7 X1 Tolerances: Value 1M 33p 1.0μ 0.1μ 0.1μ 1.0μ 1.0μ 33p 1.008MHz or 4.032 MHz R = ±10% C = ±20% Notes: 1. Bias may be decoupled to VSS and VDD using C2 and C6 when input signals are referenced to the bias pin. For input signals referenced to VSS, decouple Bias to VSS using C2 only. 2. Use C5 when input signals are referenced to VSS to decouple VDD. 3. 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. 4. The value of C7 reduces XTAL voltage overshoot. Refer to MX-COM's Crystal Oscillator Application Note (see Appendix). 5. X1 can be either a 1.008 MHz or 4.032 MHz crystal, depending on the Clock Rate setting. Figure 2 - External Component Connections MX439P package discontinued MX439 MX-COM, Inc./Doc.#2048-0041.005 Page 3 DIAGRAMS Figure 3 - Typical Variation of “B.E.R.” with Input Signal Level Figure 4 -MX439 Test Setup Figure 5- Transmitter Timing Diagram NOTES: 1. All timings are related to the TX SYNC OUTPUT. 2. 0.833ms for 1.008MHz or 4.032MHz Xtal. Page 4 3. 2ms min. + crystal tolerance. 4. DC = Don't Care. DV = Data Valid. MX439P MX439package discontinued MX-COM, Inc./Doc.#2048-0041.005 SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS OPERATING LIMITS Exceeding the maximum rating can result in device damage. Operation of the device outside the operating limits is not suggested. All charactistics are measured using the standard test circuit (Figure 4) with the following test parameters and is valid for all tests unless otherwise stated: Supply Voltage Input Voltage at any pin (ref VSS = 0V) Sink/Source Current (Total) Total Device Dissipation @ TAMB = 25°C Derating Operating Temperature Storage Temperature -0.3 to 7.0 V -0.3 V to VDD + 0.3 V 20mA 800mW max. 10 mW/°C -40°C to +85°C -55°C to +125°C VDD = +5V TAMB = 25°C Xtal (X1) Frequency: 1.008MHz 0dB reference = 300 mVrms Noise (band limited 5kHz gaussian white noise) SNR ratio measured in bit rate bandwidth (1200Hz) Characteristics See Note Static Values Supply Volts Supply Current: RX Enabled, TX Disabled RX Enabled, TX Enabled RX Disabled, TX Disabled Logic “1” level Logic “0” level Digital Output Impedance Analog and Digital Input Impedance TX Output Impedance On-Chip Crystal Oscillator: Rin Rout Inverter Gain Gain Bandwidth Product Crystal Frequency Crystal Frequency Dynamic Values Receiver: Signal Input: Dynamic Range (50dB SNR) Bit Error Rate: 12dB SNR 20dB SNR Receiver Synchronization 12dB SNR: Probability of Bit 8 being correct Probability of Bit 16 being correct Carrier Detect Sensitivity Probability of Carrier Detect being high: 12dB SNR after Bit 8 12dB SNR after Bit 16 0dB Noise (No Signal) Min. Typ. Max. Unit 4.5 5.0 5.5 V 80%VDD 100 - 3.6 4.5 650 4 10 20%VDD - mA mA μA V V kΩ kΩ kΩ 1.008 4.032 15 20 - MΩ kΩ dB 1,9 1,10 10 5 10 3 x 106 - MHz MHz 2,3 100 230 1000 mVrms 3 3 - 7.0 1.0 - 10-4 10-8 99 99.5 - % % - 6 4 6,7 - - 125 mVrms 4,8 4,8 8 - 98 99.5 5 - % % % MX439P package discontinued MX439 MX-COM, Inc./Doc.#2048-0041.005 Page 5 Characteristics (cont.) Transmitter Output TX Output Level Output Level Variation 1200/1800Hz Output Distortion 3rd Harmonic Distortion Logic “1” Carrier Frequency Logic “0” Carrier Frequency Isochronous Distortion 1200Hz - 1800Hz 1800Hz - 1200Hz See Note Min. Typ. Max. Unit 5 5 760 0 - 860 3 2 1200 1800 960 ±1.00 5 3 - mVrms dB % % Hz Hz - 25 20 40 40 μs μs Notes: 1. Crystal frequency, type and tolerance depends on system requirements. 2. See Figure 3. 3. SNR (Bit Rate Bandwidth). 4. See Figure 2, Note 3. 5. Depending on crystal tolerance. 6. 10101010101... pattern. 7. Measured with 100 mVrms signal (No noise). 8. 0dB level for CD probability measurements is 230mVrms. 9. Clock rate pin at logic “0.” 10. Clock rate pin at logic “1.” NOTES: 1. Internal delay typically 1.5ms. 2. From freely running to Sync in 8 data bits (See spec). 3. Undetermined state: 2μs max. 4. Min 800μs, Max. 865μs. Figure 6 - Receiver Timing Diagram Page 6 Figure 7 - Receiver B.E.R. vs SNR MX439P MX439package discontinued MX-COM, Inc./Doc.#2048-0041.005 ORDERING INFORMATION Fig.8 - MX439 LH Fig.9 - MX439 DW Package Outlines The MX439 is available in the package styles outlined on the following pages. Pin1 identification marking is shown on the relevant diagram and pins on all package styles number anticlockwise when viewed from the top. Fig.10 - MX439 P Handling Precautions The MX429A is a CMOS LSI circuit which includes input protection. However precautions should be taken to prevent static discharges which may cause damage. Fig.10 - MX439 J MX439P package discontinued MX439 MX-COM, Inc./Doc.#2048-0041.005 Page 7 MX439P package discontinued 4800 Bethania Station Road • Winston-Salem, NC 27105-1201 • 800 638-5577 • Fax 910 744-5054