Order this document by MC13173/D The MC13173 is a low power infrared integrated system (IRIS). It is a unique blend of a split IF wideband FM receiver and a specialized infrared LED transmitter. This device was designed to provide communications between portable computers via a half duplex infrared link at data rates up to 200 kbps. The receiver includes a mixer, IF amplifier and limiter and data slicer. The IF amplifier is split to accommodate two low cost cascaded filters. The RSSI output is derived by summing the output of both IF sections. The transmitter section includes a frequency synthesizer, FSK modulator, harmonic low pass filter and an IR LED driver. • Transmitter Operates in Two Modes: – On/Off Pulsing for Remote Control – FSK Modulation at 1.4 MHz for Data Communications • Over 70 dB of RSSI Range • • • INFRARED TRANSCEIVER SEMICONDUCTOR TECHNICAL DATA FTB SUFFIX PLASTIC PACKAGE CASE 873 (Thin QFP) 32 1 Split IF for Improved Filtering and Extended RSSI Range Digitally controlled Via a Six Line Interface Bus Individual Circuit Blocks Can Be Powered Down When Not In Use for Power Conservation ORDERING INFORMATION Device Operating Temperature Range Package MC13173FTB TA = – 40° to +85°C TQFP–32 Simplified Block Diagram 12 M 1 32 kHz Ref Ma PLL Tx PLL 14 MHz Ref T Data In E IR LED Driver 32 31 30 29 28 27 26 25 FSK Modulator Master VCO/PLL V EE1 2 R 3 RF In1 4 RF In2 5 Mixer Out 6 Harmonic LPF Mode Select Driver 24 LED Driver Feedback 23 V EE3 22 Data Out 21 VEE2 20 Data Slicer In 19 Demod 18 Quad Coil 17 Carrier Detect Data Slicer Mixer VReg1 IF Amplifier Limiter VCC1 7 VReg2 IF In 8 9 10 11 12 13 14 15 16 IF Dec1 IF Dec2 IF Out VCC2 Lim In Lim Dec1 Lim Dec2 RSSI This device contains 914 active transistors. Motorola, Inc. 1996 MOTOROLA ANALOG IC DEVICE DATA Rev 0 1 MC13173 MAXIMUM RATINGS Symbol Value Unit Power Supply Voltage Rating VCC – VEE 6.0 Vdc Junction Temperature TJ 150 °C Storage Temperature Tstg – 55 to +150 °C NOTE: Devices should not be operated at or outside these values. The “Recommended Operating Conditions” table provides for actual device operation. RECOMMENDED OPERATING CONDITIONS Characteristic Symbol Power Supply Voltage Value Unit VCC – VEE 2.7 to 5.5 Vdc TA – 40 to +85 °C Ambient Temperature Range DC ELECTRICAL CHARACTERISTICS (TA = +25°C, VCC = 3.3 Vdc, fREF = 32.768 kHz. Measured using test circuit in Figure 1, unless otherwise noted.) Characteristic Supply Current (See Table 2) Receive Mode Communications Mode A/V Mode Standby Mode Control Pin Logic State T 0 1 1 0 R 1 0 0 0 Pin Symbol 7, 12 ICC E 0 0 1 0 Min Typ Max Unit – – – – 6.5 4.75 1.5 <10 9.0 8.0 – – mA nA 31 IMA – ± 25 – µA Data Slicer Threshold Voltage 20 VTH1 0.85 1.1 1.4 Vdc Maximum Pull–Down Current 22 IDS 1.0 1.8 – mA Carrier Detect Threshold Voltage 16 VTH2 1.0 1.15 1.3 Vdc Maximum Pull–Down Current 17 ICD 1.1 3.0 – mA Maximum Pull–Up Current 25 IOH 5.8 7.0 – mA Maximum Pull–Down Current 25 IOL – 150 700 µA DC Output Voltage 24 VO – 200 – mV Transmit PLL Charge Current 30 ITX – ± 25 – µA Master PLL Charge Current DATA SLICER CARRIER DETECT TRANSMITTER AC ELECTRICAL CHARACTERISTICS (TA = +25°C, VCC = 3.3 Vdc, fREF = 32.768 kHz. Measured using test circuit in Figure 1, unless otherwise noted.) Characteristic Pin Symbol Min Typ Max Unit Upper Sideband Frequency (Mark) 24 fHI – 1.427 – MHz Lower Sideband Frequency (Space) 24 fLO – 1.317 – MHz Upper and Lower Sideband Amplitude 24 VSB 40 54 70 mVrms 4, 19 VSIN – 5.0 – µV 4, 5, 6 AV(Mix) – 23.5 – dB 6 ZO – 330 – Ω TRANSMITTER RECEIVER Receiver Sensitivity – 12 dB SINAD MIXER Mixer Conversion Gain Mixer Output Impedance 2 MOTOROLA ANALOG IC DEVICE DATA MC13173 AC ELECTRICAL CHARACTERISTICS (continued) (TA = +25°C, VCC = 3.3 Vdc, fREF = 32.768 kHz. Measured using test circuit in Figure 1, unless otherwise noted.) Characteristic Pin Symbol Min Typ Max Unit 8, 11 – – 54 – dB IF Amplifier RSSI Slope 16 – – 275 – nA/dB Input Impedance 8 ZIN – 330 – Ω Output Impedance 11 ZO – 330 – Ω RSSI Current Range 16 – – 20 – µA RSSI Dynamic Range 16 – – 70 – dB Input Impedance 13 ZIN – 330 – Ω Limiter RSSI Slope 16 – – 360 – nA/dB RSSI Current Range 16 – – 20 – µA RSSI Dynamic Range 16 – – 58 – dB IF AMPLIFIER IF Amplifier Gain LIMITING AMPLIFIER Figure 1. Test Circuit MC33202 10 k 0.001 µF 127 k 100 k 0.1 µF 10 k 100 k 200 k VEE 100 nF VCC 24.9 k VCC VCC VCC VCC – 1V 100 p 10 k 100 k VCC – 1V 10 nF 100 p 20 p 100 k 36 k 10 k VCC VCC VCC 0.001 µF VCC 0.1 µ H VCC VCC 100 pF 100 p 0.3 µ H MV209 10 p 50 VCC 0.1 µ F VCC MV209 VCC 2N2222A 32 0.001 µ F 0.1 µ H VCC 1 24 VCC 10 k 100 n VEE 10 k VCC 0.1 µF 100 + V 33 µ F EE 200 LPF 10 k 25 VCC VEE 100 n MC13173 ATTEN 10 k VCC F1 VEE 8 330 Ω 50 Ω V CC 0.1 µ F V CC 17 9 16 100 n 1.0 n 0.1 µ F 330 Ω VCC VCC 100 n 0.1 µ F 1.0 n 150 p 1.0 µ H VCC VCC MOTOROLA ANALOG IC DEVICE DATA 0.1 µ F 6.81 k VCC 1.0 n 1.0 n VCC 50 Ω VCC 3 MC13173 CIRCUIT DESCRIPTION General The MC13173 infrared transceiver integrates a split IF wideband FM receiver and an IR LED transmitter into a single IC. The transmitter is comprised of an FSK modulator, harmonic low pass filter, and IR LED driver. The receiver consists of a mixer, IF amplifier and limiting IF, detector, and data slicer. It includes RSSI and carrier detect functions. The transmitter is capable of two modes of operation. It was primarily designed for use in the Communications Mode, which enables point–to–point data links, such as the communication from keyboard to computer, or for the exchange of data between portable computers. In this mode it is capable of 200 kbps half duplex FSK operation. The transmitter can also operate in an “A/V” Mode, which pulses the LED on and off with no carrier. (See Figure 11). Digital Interface Bus The MC13173 is controlled via a six line 3.3 V digital interface bus. That includes three control pins, data in and out pins, and a carrier detect pin. Listed below is a brief description of each pin and its function. Table 1. Digital Interface Pin Descriptions Pin Pin Name Symbol I/O Description 28 Transmit Enable T I High – Transmitter is enabled Low – Transmitter is disabled 27 Data In DI I Data Input – 38.2 kbps Communication Mode 3 Receive Enable R I High – Receiver is enabled Low – Receiver is disabled 22 Data Out DO O Demodulated Output Signal 17 Carrier Detect CD O High – Carrier is present Low – Carrier is not present 26 Transmit Modulation Enable E I High – Transmitter is in A/V Mode Low – Transmitter is in Communications Mode This transceiver was designed for use in battery powered, hand–held consumer products. To minimize power consumption, the digital interface enables individual system blocks to be powered down while not in use. The following diagram shows the mode of the IC and the power state of each circuit block for a given set of control levels. Table 2. Power State Table Control Pins* Circuit Block Power States (See Figures 2 and 3) Master VCO FSK Modulator Off Off Receiver LED Driver Supply Current (Typical) Off Off 10 nA T R E 0 0 0 OFF 0 0 1 OFF Off Off Off Off 70 µA 0 1 X Receive On Off On Off 6.5 mA 1 1 1 Receive On Off On On 7.5 mA 1 1 0 Transmit – Comm Mode On On On On 9.0 mA 1 0 0 Transmit – Comm Mode On On Off On 4.75 mA 1 0 1 Transmit – A/V Mode Off Off Off On 1.5 mA M d Mode * With Data In Pin Low 4 MOTOROLA ANALOG IC DEVICE DATA MC13173 Master VCO/PLL The master VCO provides the reference frequency for the FSK modulator and the LO frequency for the receiver downconverter. With a 32.768 kHz input frequency to the master VCO on Pin 1, the LO frequency for the receiver will be at 12.075 MHz. The reference frequency for the FSK modulator will be at approximately 1.1 MHz. The master VCO and FSK modulator are not used when the transmitter is used in A/V mode, and both are powered down. Receiver Description The single conversion receiver portion of the MC13173 is low power and wideband, and incorporates a split IF. This section includes a mixer, IF amplifier, limiting IF, quadrature detector and data slicer. Mixer The mixer is a double balanced four quadrant multiplier. It can be driven either differentially or single–ended by connecting the unused input to the positive supply rail. The buffered output is internally loaded for an output impedance of 330 Ω for use with a standard ceramic filter. IF Amplifier The first IF amplifier section is composed of three differential stages with the second and third stages contributing to the RSSI. This section has internal DC feedback and external input decoupling for improved symmetry and stability. The total gain of the IF amplifier block is approximately 40 dB. The fixed internal input impedance is 330 Ω for use with a 10.7 MHz ceramic filter. The output of the IF amplifier is buffered and the impedance is 330 Ω. Limiter The limiter section is similar to the IF amplifier section, except that four stages are used with the last three contributing to the RSSI. This IF limiting amplifier section drives the quadrature detector internally. RSSI/Carrier Detect The received signal strength indicator (RSSI) outputs a current proportional to the log of the received signal amplitude. The RSSI current output is derived by summing the currents from the IF and limiting amplifier stages. An external resistor sets the output voltage range. The carrier detect threshold is set at approximately 1.2 Vdc. When the RSSI level exceeds that threshold, the MOTOROLA ANALOG IC DEVICE DATA carrier detect output will go high. A large resistor may be added externally between the comparator output and the positive input for hysteresis. Quadrature Detector The demodulator is a conventional quadrature type with an external LC tank driven through an internal 5 pF capacitor. The output is buffered to give an output impedance of less than 1.0 kΩ at an average DC level of around 1.1 V. Data Slicer The data slicer is designed to square up the data signal. It is self centering at about 1.1 V, and clips at about 0.75 V and 1.45 V. There is a short time constant for large peak–to–peak voltage swings or when there is a change in DC level at the detector output. The time constant is longer for small signals or for continuous bits of the same polarity which drift close to the threshold voltage. Transmission Description The MC13173 uses a dual modulus PLL to frequency shift key (FSK) modulate the baseband digital input signal, producing the necessary logic high and low frequencies for transmission. The transmit frequency for a logic high is 1.427 MHz, and the frequency for a low is 1.317 MHz with a 32.768 kHz reference frequency. FSK Modulator In the communications mode, the FSK modulator uses the reference frequency from the Master VCO to produce the two frequencies required for a logic high and a logic low. In the A/V mode, the FSK modulator is not used and is powered down. LED Driver Stage A low pass filter following the FSK modulator removes the undesired harmonic frequencies from the square–wave output of the divider circuits in PLLs. The resulting sinusoidal waveforms are fed into a unity gain difference amplifier, which drives the base of an external transistor, modulating the IR LED. In A/V mode, the data is input directly into the inverting input of the op amp, and the low pass filter is not used. 5 MC13173 DOCUMENT CONTAINS SCANNED IMAGES WHICH COULD NOT BE PROCESSED FOR PDF FILES. FOR COMPLETE DOCUMENT WITH IMAGES PLEASE ORDER FROM MFAX OR THE LITERATURE DISTRIBUTION CENTER 6 MOTOROLA ANALOG IC DEVICE DATA MC13173 Figure 2. Transmitter Block Diagram VCC fR VCC PFD/ Charge Pump ÷2 PFD/ Charge Pump LED Driver Stage fM1 FSK Modulator Master VCO ÷67 fLO ÷12 ÷13 ÷11 fM2 Harmonic LPF LED Driver ÷10 VCC Data In (Comm Mode) Data In (A/V Mode) fR = 32.768 kHz fLO = 67 X 11 fR 2 13 f 11 X 10 LO 12 Data Low: fM2 = f 11 X 10 LO Data High: fM1 = Figure 3. Receiver Block Diagram fR ÷2 PFD/ Charge Pump Master VCO Receiver fLO ÷11 ÷67 VReg1 Carrier Detect VCC Mixer IF Amplifier Limiter VReg2 RSSI Detector Data Output RF Input VCC MOTOROLA ANALOG IC DEVICE DATA 7 MC13173 Table 3. PIN FUNCTION DESCRIPTION (TA = 25°C, VCC = 5.0 Vdc, fREF = 32.768 kHz, fMOD = 32.768 kHz) Pin Symbol Description 1 12 M VCO for Master PLL. Internal Equivalent Circuit Waveform VCC (Measured using a low capacitance FET probe. Standard oscilloscope probes can pull oscillator off frequency. See Figure 14.) 1 VEE 2, 21, 23 VEE DC ground. Should be connected to a continuous ground plane on the PCB. 3 R Receive Enable Pin. See Tables 1 & 2. 4, 5 RF In1 RF In2 RF Input to the mixer. 1.375 MHz average carrier frequency with ± 50 kHz deviation. VCC 4 5 VEE 6 Mixer Out 10.7 MHz IF VCC ZO = 330 Ω RF In = – 20 dBm Modulation = 32.768 kHz 6 VEE 7, 12 VCC Supply voltage and RF ground, should be decoupled to VEE. 8 IF In IF input impedance is 330 Ω. RF In = – 20 dBm Modulation = 32.768 kHz VCC 10 8 9 VEE 8 MOTOROLA ANALOG IC DEVICE DATA MC13173 Table 3. PIN FUNCTION DESCRIPTION (continued) (TA = 25°C, VCC = 5.0 Vdc, fREF = 32.768 kHz, fMOD = 32.768 kHz) Pin Symbol 9, 10 IF Dec IF decoupling as shown in Figure 15. 11 IF Out IF Output. Internal Equivalent Circuit Description Waveform See Circuit for Pin 8. VCC ZO = 330 Ω. –20 dBm RF input level. Output is sinusoidal with lower drive levels. 11 VEE 13 Lim In Limiter input. VCC ZIn = 330 Ω. 15 13 14, 15 Lim Dec External limiter decoupling as shown in application circuit. 14 VEE 16 RSSI Received Signal Strength Indicator Output. (See Figure 13) 17 Carrier Detect Logic output of the carrier detect comparator. 17 VEE 18 Quad Coil Quadrature tuning circuit. 18 VCC Modulated 10.7 MHz IF. Measured with a low capacitance FET probe. 5p VEE 19 Demod Demodulated signal output measured at the pin (before filtering). VCC Modulation = 32.768 kHz sine wave. 19 VEE MOTOROLA ANALOG IC DEVICE DATA 9 MC13173 Table 3. PIN FUNCTION DESCRIPTION (continued) (TA = 25°C, VCC = 5.0 Vdc, fREF = 32.768 kHz, fMOD = 32.768 kHz) Pin Symbol Description 20 Data Slicer In Input from the receiver demodulated output. 22 Data Out Internal Equivalent Circuit Waveform Output from the receiver data slicer. Modulation = 32.768 kHz sine wave. RF input driven by frequency generator. See also Figure 10. 24 LED Driver Feedback Feedback for the LED driver op amp. 25 IR LED Driver Output of the unity gain output buffer in Communications Mode. See Figure 11 for transmit output in A/V mode. VCC 24 Modulation = 32.768 kHz square wave. 25 25 k . VEE 26 E Transmit Modulation Enable. See Tables 1 & 2. 27 Data In Modulation input for transmit data. 28 T Transmit Enable pin. See Tables 1 & 2. 29 14 MHz Ref VCO for FSK Modulator phase locked loop. (Measured using a low capacitance FET probe. Standard oscilloscope probes can pull oscillator off frequency. See Figure 14.) VCC 29 No modulation (Data In low). VEE 10 MOTOROLA ANALOG IC DEVICE DATA MC13173 Table 3. PIN FUNCTION DESCRIPTION (continued) (TA = 25°C, VCC = 5.0 Vdc, fREF = 32.768 kHz, fMOD = 32.768 kHz) Pin Symbol Description 30 Tx PLL Phase detector output for the FSK Modulator. Internal Equivalent Circuit Waveform (With loop closed and locked.) No modulation (Data In low). VCC 30 With 32.768 kHz square wave modulation. VEE Note: Probing the output of the phase detectors directly may disturb the loop. It is best to probe the output of the op amp when evaluating loop response. 31 Ma PLL Output of the phase detector charge pump for the Master PLL. VCC (With loop closed and locked.) 31 VEE 32 32 kHz Ref Input to 32.768 kHz reference. Filtered from TTL oscillator using application circuit in Figure 15. Approximately 1.0 Vp–p triangle wave at 32.768 kHz. VCC 32 VEE MOTOROLA ANALOG IC DEVICE DATA 11 MC13173 Typical Performance Over Temperature (Measured using test circuit in Figure 1) Figure 5. Normalized IF Amp Gain versus Temperature Figure 4. Normalized Mixer Gain versus Temperature 1.0 NORMALIZED IF AMP GAIN NORMALIZED MIXER GAIN 1.0 0.5 0 –0.5 0 50 –0.5 –1.0 – 50 100 Figure 7. Maximum Pull–Down Current versus Temperature (Pin 25) 0 50 100 140 130 120 110 100 90 80 70 60 – 50 0 50 100 TA, AMBIENT TEMPERATURE (°C) TA, AMBIENT TEMPERATURE (°C) Figure 9. Data Slicer and Carrier Detect Threshold Voltages versus Temperature Figure 8. Supply Current versus Temperature – 4.5 1.5 VTH, THRESHOLD VOLTAGE (V) ICC , SUPPLY CURRENT (mA) 100 Figure 6. Maximum Pull–Up Current versus Temperature (Pin 25) 6.0 – 5.0 Transmit Communications Mode – 5.5 – 6.0 Receive Mode – 6.5 0 50 TA, AMBIENT TEMPERATURE (°C) 12 50 TA, AMBIENT TEMPERATURE (°C) 6.5 –7.0 – 50 0 TA, AMBIENT TEMPERATURE (°C) 7.0 5.5 – 50 0 IO , MAXIMUM PULL–DOWN CURRENT ( µ A) IO , MAXIMUM PULL–UP CURRENT (mA) –1.0 – 50 0.5 100 1.25 Carrier Detect Data Slicer 1.0 0.75 – 50 0 50 100 TA, AMBIENT TEMPERATURE (°C) MOTOROLA ANALOG IC DEVICE DATA MC13173 APPLICATIONS INFORMATION The MC13173 transceiver is specially designed to operate from a 32.768 kHz reference which is readily available in most computer applications. The frequency synthesizer on chip generates a receiver local oscillator frequency and the transmit mark and space frequencies from this fixed reference frequency, eliminating the need for additional crystals or manual tuning. Large divide ratios are needed to generate these frequencies, however. For example, the receiver LO frequency is 368.5 times the 32.768 kHz reference frequency. This requires that the reference frequency be both accurate and stable. A two percent error in the reference frequency would pull the LO off frequency by over 240 kHz, putting the IF frequency out of the usable bandwidth of the filters and discriminator. For this reason, a 32.768 kHz oscillator circuit has been included on the demonstration board design. Although TTL crystal oscillators are available, this oscillator circuit uses an inexpensive tuning fork crystal and a hex inverter to generate a square wave reference frequency, which is then filtered and level adjusted to a 1.0 Vp–p triangle wave to drive pin 32. A TTL Clock Oscillator could also be used with the filter circuit as shown. Frequency Synthesizer The recommended op amp for the external loop filter is the MC33202. For low voltage operation, (VCC ≤ 3.3 V) an op amp that is rail–to–rail on both the input and output is advisable to obtain the widest possible output voltage range without distortion. Sufficient distortion from the op amp such as phase reversal on the output caused by overdriving the inputs could prevent the loop from locking to the reference. In debugging the loop filter, it is important to note that the FSK Modulator phase locked loop will not lock until the Master VCO is locked to the reference. If the application circuit in Figure 15 is used, both loops should lock without the need for any additional tweaking. Since the VCO has ± 2.0 MHz of range using the MV209 varactor diode (see Figure 11), neither precision components nor tuning should be required. To ensure both loops are operating properly, first evaluate each VCO with the loop open and a voltage equal to VCC/2 applied to the resistor in series with the varactor. Since there is a relatively small capacitance (<40 pF) in series with the LC tank circuit, the VCO pin is sensitive to any parasitic capacitance. Thus when using a standard oscilloscope probe having 10 to 20 pF capacitance it is difficult to measure the VCO frequency without shifting its frequency. A low capacitance FET probe used with a frequency counter will enable you to accurately measure the VCO frequency without altering it in the process. The free running frequency of the VCO should be approximately on frequency when the loop is open and the varactor is biased at mid–supply. The VCO for the Master PLL should run at 12.05 MHz. The free running frequency of the FSK Modulator should be at 13.72 MHz, midway between the two VCO frequencies needed to generate the transmit mark and space frequencies. The FSK Modulator loop is only active when the transmitter is enabled and the device is in the communications mode (see Tables 1 & 2). If either the “T” pin is low or the “E” pin is high, the VCO will be off and you will see no oscillation on Pin 29. Once the loops are closed, the VCO frequencies should track the reference frequency within the hold–in range of the MOTOROLA ANALOG IC DEVICE DATA loop. Although the FSK Modulator loop is dependent on the Master VCO, the Master VCO is completely independent of the FSK Modulator. In fact, the FSK Modulator can be powered down (see Table 2) without affecting the Master VCO operation. In the application circuit in Figure 15 a single reference voltage for both op amps in the loop filters is provided by two diodes to VCC. If the Master VCO is affected by the FSK Modulator loop, this generally indicates a problem with the common reference voltage to the op amp, and may mean the diodes are in backwards. Once the loops are closed you should see a phase detector output such as is shown in the Pin Function Description in Table 3. If the VCO was on frequency when the loop was open, the phase detector outputs should swing around mid supply and not hit against either the positive or negative rail. Latching to VCC or VEE may indicate the loop filter circuitry is not implemented correctly. Due to the digital design of the phase detectors, the transmitter can only transition between mark and space frequencies on a clock edge. On the receive side this may be seen as a double image on the detector output, with a discrete time delay which does not vary with the frequency of the data input (see Figure 10). This is a normal consequence of using a digital phase detector and should not be confused with jitter from the data slicer. Figure 10. Receive Data Output (Data Transmitted from Companion MC13173) Transmitter The light emitting diode (LED) driver in the transmitter is capable of 6.0 to 10 mA of pull–up current. Selection of the external transistor and biasing resistor will depend on the LEDs used. Typical infrared LEDs require 50 to 100 mA of current and have a forward voltage of 1.5V. Sufficient current is needed to obtain the maximum power output without distorting the output by overdriving the LED. Key specifications include rise and fall time, wavelength, beam width (generally given in half–angle), maximum power output and efficiency. Choice of wavelengths is generally determined by cost and power efficiency, which may vary between vendors. The LEDs used in this application are at 880 nm and were chosen for best efficiency. However LEDs in general are very inefficient, converting only 1 or 2 percent of the electrical power into optical power. Multiple LEDs can be used to increase transceiver range. 13 MC13173 Disabling the transmitter via the data bus turns off the output of the LED driver, removing the base current from the external transistor and thereby turning off the IR LED. Because of the high current drawn by the LED, this offers considerable power savings when the transmitter is not in use and can be easily controlled by a microcontroller with no additional circuitry. In the “A/V” transmit mode, the data output is on/off keyed, with the LED on for a data high, and off for a data low. It is a baseband signal, with no carrier present (see Figure 11). harmonics. In the application circuit in Figure 15, Toko filters with a bandwidth of 330 kHz or 360 kHz are recommended to accommodate higher data rates. If the IF filters are too narrow, the recovered signal may have noise on the peaks (see Figure 12). Figure 12. Receive Data Output Figure 11. LED Driver Output in A/V Mode Receiver The receiver portion of the MC13173 is similar to the design of Motorola’s MC13156 Wideband FM Receiver. Instead of using the mixer to downconvert from a higher RF frequency, this application is designed to upconvert the 1.372 MHz input to a 10.7 MHz IF. The wide deviation, relative to the RF input frequency, requires a low Q tuned circuit to recover this bandwidth: Q [ BWfc 3 dB , where f c + 1.372 MHz By Carson’s Rule, the BW = 2(fdev + fmod). Since for mark/space frequencies of 1.317 MHz and 1.427 MHz the deviation is fixed at ±50 kHz, the bandwidth for a 50 kHz square wave (100 kbps) would be 200 kHz, and the tuned input requires a Q of less than 7. The low Q of the tank circuit reduces both the selectivity and the sensitivity of the receiver. For a Q of 7, the resistor required across the 56 µH inductor can be calculated: R = QXL = (7) • (2π) • (1.372 E6) • (56 E–6) R = 3.3 kΩ The RSSI has over 70 dB of dynamic range and 20 µA of current range. The RSSI output provides the input to the carrier detect comparator (see Figure 13) and a logarithmic output proportional to the input signal level. It can, therefore, be used to recover amplitude shift keyed (ASK) data. The key specifications for the infrared detectors are response time, sensitivity, acceptance angle, and wavelength. Some vendors offer detectors in a black package with a built–in daylight filter. Although the transparent packages offer better sensitivity, the detectors with the daylight filter offer a much better signal to noise ratio. Response time (or maximum frequency) of the system is generally limited by the capability of the emitters rather than the detectors. For this application, a rise and fall time of 500 ns is sufficient. Design and Layout Considerations Although the frequencies in this design are low by RF standards, careful layout and good decoupling are still good practice. The high gain limiter and IF blocks should be decoupled as shown in the application circuit as near the IC as possible for best receiver performance. Also the TTL levels from the reference oscillator and the wide current swing applied to the IR LEDs can easily be picked up on VCC, creating problems for the sensitive phase detector circuits and receiver RF inputs. Avoid long parallel traces and use plenty of decoupling to keep the supply rail clean. The 10.7 MHz ceramic filters also need to be wide enough to pass the full frequency range which will include some 14 MOTOROLA ANALOG IC DEVICE DATA MC13173 Typical Performance (Measured using Application Circuit in Figure 15) Figure 14. VCO Frequency versus Varactor Voltage Figure 13. RSSI Output Current versus RF Input Level 16 15 25 VCO FREQUENCY, (MHz) RSSI OUTPUT CURRENT (µ Adc) 30 20 15 10 14 FSK Modulator 13 12 Master PLL 11 10 5.0 – 140 –120 – 100 – 80 – 60 – 40 – 20 9.0 – 0.5 20 0 0 1.0 0.5 1.5 2.0 2.5 3.00 3.5 VARACTOR VOLTAGE (V) RF INPUT LEVEL (dBm) Figure 15. Application Circuit MC33202 VCC 110 k 10 nF VCC VCC 1.0 nF 110 k 100 k X1 1.0 nF 2.0 M VEE 220 k 10 k 100 nF 24 k VCC 220 k 24 k VCC VCC VCC 10 p 3.9 µH 270 p 20 k VCC VCC 1.0 n MV209 10 k SFH485–2 VCC VCC 0.68 + µF MV209 470 p MPS3904 62 k 4.7 µH 32 25 1 VCC 10 k VCC 24 V V 100 n CC CC VCC 10 k 10 k 100 p 2.2 k 8.2 k 82 µH 390 p 100 n 15 k SFH206K MPF102 3.6 k F1 180 p 2.0 k 510 VCC 8 17 9 16 100 n VCC 2.2 n NOTES: 1) F1 & F2 – 10.7 MHz ceramic filter, Toko 107MA–AE–10 1.0 n (360 kHz), Toko 107M0 AE–10 (330 kHz) or equivalent. 2) Tunable shielded inductors: 56 µH Toko A119ANS–T1042Z 1.0 µH Toko 292KNS–T1372Z 82 µH Toko A119ANS–T1044Z 1.5 µH Toko 292KNS–T1373Z 3) Crystal – 32.768 kHz C – Type tuning fork crystal. Digikey part number SE3201 or equivalent. 4) LEDs and Detectors SFH484–2, SFH485–2 and SFH206K are made by Siemens. 5) Optimum bias resistor depends on the LEDs used. 6) May be fixed or tunable. MOTOROLA ANALOG IC DEVICE DATA 33 n 10 k VCC 33 n 3.0 k VCC 100 n 10 (See Note 5) 2.2 M MC13173 220 p 56 µH SFH484–2 20 k 36 k 1.0 µF 100 µH (See µ Note 6) 10 + VCC 100 nF VCC 10 k 200 p 10 k 1.0 k 10 nF 1N4001 MC74HCU04 VCC 1.0 µ + 100 k 100 n 1.0 n VCC 1.5 µ VCC F2 1.0 n 150 p 110 k 1.0 n 47 k 0.01 µF VCC 15 MC13173 Figure 16. Detailed Internal Block Diagram 32K 32 12M 1 D 27 E 26 CLK_DIV2 D_en PFD OSC MaPLL 31 2 VEE1 3R MXR 4 RFin1 5 RFin2 DIV11 DIV67 6 MIXout 7 VCC1 8 IFin E_en 9 IFdec1 10 IFdec2 PFD TxPLL 30 IF DIV12_13 11 IFout 12 VCC2 13 LIMin OSC DIV10 14 LIMdec1 15 LIMdec2 LIM LPF_DRV LED Driver 25 RSSI LED Feedback 24 16 RSSI T 28 17 Carrier Detect 14M 29 DET 18 Quad Coil 19 Demod 20 DSin 21 VEE2 DS 22 DATAout 23 VEE3 16 MOTOROLA ANALOG IC DEVICE DATA MC13173 OUTLINE DIMENSIONS FTB SUFFIX PLASTIC TQFP PACKAGE CASE 873–01 L 24 17 B DETAIL A 32 D S H A–B V M L 0.20 (0.008) –B– –A– 0.20 (0.008) M C A–B 0.05 (0.002) A–B S D S 16 S 25 B 9 1 P B 8 –D– A 0.20 (0.008) M C A–B 0.05 (0.002) A–B –A–,–B–,–D– S D S D S DETAIL A S 0.20 (0.008) H A–B M S F BASE METAL DETAIL C M J C E –H– –C– SEATING PLANE H M G N DATUM PLANE 0.01 (0.004) D 0.20 (0.008) M C A–B S D S SECTION B–B VIEW ROTATED 90° CLOCKWISE U T R –H– DATUM PLANE K X DETAIL C MOTOROLA ANALOG IC DEVICE DATA Q NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DATUM PLANE –H– IS LOCATED AT BOTTOM OF LEAD AND IS COINCIDENT WITH THE LEAD WHERE THE LEAD EXITS THE PLASTIC BODY AT THE BOTTOM OF THE PARTING LINE. 4. DATUMS –A–, –B– AND –D– TO BE DETERMINED AT DATUM PLANE –H–. 5. DIMENSIONS S AND V TO BE DETERMINED AT SEATING PLANE –C–. 6. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION. ALLOWABLE PROTRUSION IS 0.25 (0.010) PER SIDE. DIMENSIONS A AND B DO INCLUDE MOLD MISMATCH AND ARE DETERMINED AT DATUM PLANE –H–. 7. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.08 (0.003) TOTAL IN EXCESS OF THE D DIMENSION AT MAXIMUM MATERIAL CONDITION. DAMBAR CANNOT BE LOCATED ON THE LOWER RADIUS OR THE FOOT. DIM A B C D E F G H J K L M N P Q R S T U V X MILLIMETERS MIN MAX 7.10 6.95 7.10 6.95 1.60 1.40 0.273 0.373 1.50 1.30 — 0.273 0.80 BSC 0.20 — 0.119 0.197 0.57 0.33 5.6 REF 8° 6° 0.119 0.135 0.40 BSC 5° 10° 0.15 0.25 8.85 9.15 0.15 0.25 5° 11° 8.85 9.15 1.0 REF INCHES MIN MAX 0.274 0.280 0.274 0.280 0.055 0.063 0.010 0.015 0.051 0.059 — 0.010 0.031 BSC 0.008 — 0.005 0.008 0.013 0.022 0.220 REF 8° 6° 0.005 0.005 0.016 BSC 5° 10° 0.006 0.010 0.348 0.360 0.006 0.010 5° 11° 0.348 0.360 0.039 REF 17 MC13173 Motorola reserves the right to make changes without further notice to any products herein. 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How to reach us: USA / EUROPE / Locations Not Listed: Motorola Literature Distribution; P.O. Box 20912; Phoenix, Arizona 85036. 1–800–441–2447 or 602–303–5454 JAPAN: Nippon Motorola Ltd.; Tatsumi–SPD–JLDC, 6F Seibu–Butsuryu–Center, 3–14–2 Tatsumi Koto–Ku, Tokyo 135, Japan. 03–81–3521–8315 MFAX: [email protected] – TOUCHTONE 602–244–6609 INTERNET: http://Design–NET.com ASIA/PACIFIC: Motorola Semiconductors H.K. Ltd.; 8B Tai Ping Industrial Park, 51 Ting Kok Road, Tai Po, N.T., Hong Kong. 852–26629298 18 ◊ *MC13173/D* MOTOROLA ANALOG IC DEVICE DATA MC13173/D