Order this document by MC13156/D The MC13156 is a wideband FM IF subsystem targeted at high performance data and analog applications. Excellent high frequency performance is achieved at low cost using Motorola's MOSAIC 1.5 bipolar process. The MC13156 has an onboard grounded collector VCO transistor that may be used with a fundamental or overtone crystal in single channel operation or with a PLL in multichannel operation. The mixer is useful to 500 MHz and may be used in a balanced-differential, or single-ended configuration. The IF amplifier is split to accommodate two low cost cascaded filters. RSSI output is derived by summing the output of both IF sections. A precision data shaper has a hold function to preset the shaper for fast recovery of new data. Applications for the MC13156 include CT-2, wideband data links and other radio systems utilizing GMSK, FSK or FM modulation. * 2.0 to 6.0 Vdc Operation * * * * * * WIDEBAND FM IF SYSTEM FOR DIGITAL AND ANALOG APPLICATIONS SEMICONDUCTOR TECHNICAL DATA DW SUFFIX PLASTIC PACKAGE CASE 751E (SO-24L) 24 1 Typical Sensitivity at 200 MHz of 2.0 V for 12 dB SINAD RSSI Dynamic Range Typically 80 dB High Performance Data Shaper for Enhanced CT-2 Operation Internal 330 and 1.4 k Terminations for 10.7 MHz and 455 kHz Filters FB SUFFIX PLASTIC QFP PACKAGE CASE 873 32 1 Split IF for Improved Filtering and Extended RSSI Range 3rd Order Intercept (Input) of -25 dBm (Input Matched) PIN CONNECTIONS Function Simplified Block Diagram LO In LO Emit 24 23 VEE1 22 CAR Det RSSI 21 20 VEE2 19 DS Hold Data Out DS Gnd DS In 18 17 16 15 Mixer Quad Demod Coil 14 13 Data Slicer Bias 5.0 pF Bias LIM Amp IF Amp 1 2 3 4 5 RF In 1 RF In 2 Mix Out VCC1 IF In 6 7 IF IF DEC 1 DEC 2 8 9 10 IF Out VCC2 LIM In 11 SO-24L QFP RF Input 1 RF Input 2 Mixer Output VCC1 1 2 3 4 31 32 1 2 IF Amp Input IF Amp Decoupling 1 IF Amp Decoupling 2 VCC Connect (N/C Internal) 5 6 7 - 3 4 5 6 IF Amp Output VCC2 Limiter IF Input Limiter Decoupling 1 8 9 10 11 7 8 9 10 Limiter Decoupling 2 VCC Connect (N/C Internal) Quad Coil Demodulator Output 12 - 13 14 11 12, 13, 14 15 16 Data Slicer Input VCC Connect (N/C Internal) Data Slicer Ground Data Slicer Output 15 - 16 17 17 18 19 20 Data Slicer Hold VEE2 RSSI Output/Carrier Detect In Carrier Detect Output 18 19 20 21 21 22 23 24 VEE1 and Substrate LO Emitter LO Base VCC Connect (N/C Internal) 22 23 24 - 25 26 27 28, 29, 30 12 ORDERING INFORMATION LIM LIM DEC 1 DEC 2 Device NOTE: Pin Numbers shown for SOIC package only. Refer to Pin Assignments Table. This device contains 197 active transistors. MC13156DW MC13156FB Operating Temperature Range TA = -40 to +85C Motorola, Inc. 1998 MOTOROLA RF/IF DEVICE DATA Package SO-24L QFP Rev 2.1 1 MC13156 MAXIMUM RATINGS Rating Pin Symbol Value Unit Power Supply Voltage 16, 19, 22 Vdc - VEE(max) TJ(max) -6.5 Junction Temperature 150 C Storage Temperature Range - Tstg -65 to +150 C NOTES: 1. Devices should not be operated at or outside these values. The "Recommended Operating Conditions" table provides for actual device operation. 2. ESD data available upon request. RECOMMENDED OPERATING CONDITIONS Rating Power Supply Voltage @ TA = 25C -40C TA +85C Input Frequency Ambient Temperature Range Input Signal Level Pin Symbol Value Unit 4, 9 16, 19, 22 VCC VEE 0 (Ground) -2.0 to -6.0 Vdc 1, 2 fin TA Vin 500 MHz -40 to +85 C 200 mVrms - 1, 2 DC ELECTRICAL CHARACTERISTICS (TA = 25C, VCC1 = VCC2 = 0, no input signal.) Pin Symbol Total Drain Current (See Figure 2) VEE = -2.0 Vdc VEE = -3.0 Vdc VEE = -5.0 Vdc VEE = -6.0 Vdc 19, 22 ITotal Drain Current, I22 (See Figure 3) VEE = -2.0 Vdc VEE = -3.0 Vdc VEE = -5.0 Vdc VEE = -6.0 Vdc 22 Drain Current, I19 (See Figure 3) VEE = -2.0 Vdc VEE = -3.0 Vdc VEE = -5.0 Vdc VEE = -6.0 Vdc 19 Characteristic Min Typ Max Unit - 3.0 - - 4.8 5.0 5.2 5.4 - 8.0 - - - - - - 3.0 3.1 3.3 3.4 - - - - - - - - 1.8 1.9 1.9 2.0 - - - - 1.0 1.1 1.2 Vdc - 1.7 - mA mA I22 mA I19 mA DATA SLICER (Input Voltage Referenced to VEE = -3.0 Vdc, no input signal; See Figure 15.) Input Threshold Voltage (High Vin) 15 Output Current (Low Vin) Data Slicer Enabled (No Hold) V15 > 1.1 Vdc V18 = 0 Vdc 17 V15 I17 AC ELECTRICAL CHARACTERISTICS (TA = 25C, VEE = -3.0 Vdc, fRF = 130 MHz, fLO = 140.7 MHz, Figure 1 test circuit, unless otherwise specified.) Characteristic Pin Symbol Min Typ Max Unit 1, 14 - - -100 - dBm Conversion Gain Pin = -37 dBm (Figure 4) 1, 3 - - 22 - dB Mixer Input Impedance Single-Ended (Table 1) 1, 2 Rp Cp - - 1.0 4.0 - - k pF Mixer Output Impedance 3 - - 330 - IF RSSI Slope (Figure 6) 20 - 0.2 0.4 0.6 A/dB IF Gain (Figure 5) 5, 8 - - 39 - dB Input Impedance 5 - - 1.4 - k Output Impedance 8 - - 290 - 12 dB SINAD Sensitivity (See Figures 17, 23) fin = 144.45 MHz; fmod = 1.0 kHz; fdev = 75 kHz MIXER IF AMPLIFIER SECTION 2 MOTOROLA RF/IF DEVICE DATA MC13156 AC ELECTRICAL CHARACTERISTICS (continued) (TA = 25C, VEE = -3.0 Vdc, fRF = 130 MHz, fLO = 140.7 MHz, Figure 1 test circuit, unless otherwise specified.) Characteristic Pin Symbol Min Typ Max Unit 20 - 0.2 0.4 0.6 A/dB Limiter Gain - - - 55 - dB Input Impedance 10 - - 1.4 - k Output Current - Carrier Detect (High Vin) 21 - - 0 - A Output Current - Carrier Detect (Low Vin) 21 - - 3.0 - mA Input Threshold Voltage - Carrier Detect Input Voltage Referenced to VEE = -3.0 Vdc 20 - 0.9 1.2 1.4 Vdc LIMITING AMPLIFIER SECTION Limiter RSSI Slope (Figure 7) CARRIER DETECT Figure 1. Test Circuit MC13156 1:4 (1) TR 1 RF Input 130MHz 50 Mixer 1 Local Oscillator Input 140.7MHz 200m Vrms 24 200 23 2 1.0 n Mixer Output 330 A 3 4 IF Input VEE VCC 22 100 n 21 Bias 5 20 50 VEE 19 A 100 n + 1.0 n Data Slicer Hold Data Output A 17 Bias 8 VEE 1.0 18 Data Slicer 1.0 n 9 Limiter Input 10 SMA RSSI Output A 7 IF Output Carrier Detect A IF Amp 6 1.0 n 1.0 n 330 + 1.0 n 1.0 VCC VEE 16 1.0 n V LIM Amp 15 100 n 1.0 n 50 1.0 n 11 1.0 n 14 12 13 100 k 100 k 5.0 p 150 p (3) 1.0 H NOTES: 1. TR 1 Coilcraft 1:4 impedance transformer. 2. VCC is DC Ground. 3. 1.5 H variable shielded inductor: Toko Part # 292SNS-T1373 or Equivalent. MOTOROLA RF/IF DEVICE DATA 3 MC13156 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 4 MOTOROLA RF/IF DEVICE DATA MC13156 Figure 2. Total Drain Current versus Supply Voltage and Temperature Figure 3. Drain Currents versus Supply Voltage 4.0 I 19 , I 22 DRAIN CURRENTS (mA) 55C 5.5 25C 5.0 -10C 4.5 -40C 4.0 3.5 1.0 MIXER GAIN (dB) TA = 25C TA = 85C 6.0 2.0 3.0 4.0 5.0 6.0 3.2 2.8 2.4 I19 2.0 2.0 3.0 4.0 5.0 6.0 7.0 VEE, SUPPLY VOLTAGE (-Vdc) Figure 4. Mixer Gain versus Input Signal Level Figure 5. IF Amplifier Gain versus Input Signal Level and Ambient Temperature 25.0 40 22.5 38 20.0 TA = 25C 17.5 15.0 10.0 -90 I22 VEE, SUPPLY VOLTAGE (-Vdc) 12.5 36 34 32 -80 -70 -60 -50 -40 -30 -20 VEE = -5.0 Vdc f = 10.7 MHz 26 -65 -10 85C 55C 25C -10C -40C 30 28 -60 -55 -50 -45 -40 -35 -30 Pin, IF INPUT SIGNAL LEVEL (dBm) Figure 6. IF Amplifier RSSI Output Current versus Input Signal Level and Ambient Temperature Figure 7. Limiter Amplifier RSSI Output Current versus Input Signal Level and Temperature 17.5 TA = 25 to 85C VEE = -5.0 Vdc f = 10.7 MHz -10C -40C 15.0 12.5 10.0 7.5 5.0 2.5 0 -50 -40 -30 -20 -10 Pin, IF INPUT SIGNAL LEVEL (dBm) MOTOROLA RF/IF DEVICE DATA 0 10 LIMITER AMPLIFIER RSSI OUTPUT CURRENT ( A) Pin, RF INPUT SIGNAL LEVEL (dBm) 20.0 IF AMPLIFIER RSSI CURRENT ( A) 3.6 1.6 1.0 7.0 IF AMPLIFIER GAIN (dB) TOTAL DRAIN CURRENT, I TOTAL (mA) 6.5 30 25 TA = 25 to 85C VEE = - 5.0 Vdc f = 10.7 MHz -10C -40C 20 15 10 5.0 0 -70 -60 -50 -40 -30 -20 -10 0 10 Pin, INPUT SIGNAL LEVEL (dBm) 5 6 19 10 12 11 9 22 23 24 4 Linear Amplifier 1 RFin1 1.0 k 2 RFin2 1.0 k Mixer 7 1.4 k Quadrature Detector 14 Demod 32 k 6 IFdec2 32 k IFdec1 Mix IFin 5 3 Output Quad coil 5.0 p 13 330 IF Amplifier 16 k 8 400 290 DS in 15 RSSI 20 Out Data Slicer IFout RSSI 64 k 64 k Carrier Detect Output 21 64 k 28 18 16 17 Carrier Detect DSHold DSGnd DS Output Figure 8. VEE2 LIM in LIMdec2 LIMdec1 V CC2 VEE1 Oemitter LO base VCC1 Local Oscillator Figure 8. MC13156DW Internal Circuit Schematic MC13156 MOTOROLA RF/IF DEVICE DATA MC13156 CIRCUIT DESCRIPTION General The MC13156 is a low power single conversion wideband FM receiver incorporating a split IF. This device is designated for use as the backend in digital FM systems such as CT-2 and wideband data links with data rates up to 500 kbaud. It contains a mixer, oscillator, signal strength meter drive, IF amplifier, limiting IF, quadrature detector and a data slicer with a hold function (refer to Figure 8, Simplified Internal Circuit Schematic). Current Regulation Temperature compensating voltage independent current regulators are used throughout. Mixer The mixer is a double-balanced four quadrant multiplier and is designed to work up to 500 MHz. It can be used in differential or in single-ended mode by connecting the other input to the positive supply rail. Figure 4 shows the mixer gain and saturated output response as a function of input signal drive. The circuit used to measure this is shown in Figure 1. The linear gain of the mixer is approximately 22 dB. Figure 9 shows the mixer gain versus the IF output frequency with the local oscillator of 150 MHz at 100 mVrms LO drive level. The RF frequency is swept. The sensitivity of the IF output of the mixer is shown in Figure 10 for an RF input drive of 10 mVrms at 140 MHz and IF at 10 MHz. The single-ended parallel equivalent input impedance of the mixer is Rp ~ 1.0 k and Cp ~ 4.0 pF (see Table 1 for details). The buffered output of the mixer is internally loaded resulting in an output impedance of 330 . Local Oscillator The on-chip transistor operates with crystal and LC resonant elements up to 220 MHz. Series resonant, overtone crystals are used to achieve excellent local oscillator stability. 3rd overtone crystals are used through about 65 to 70 MHz. Operation from 70 MHz up to 180 MHz is feasible using the on-chip transistor with a 5th or 7th overtone crystal. To enhance operation using an overtone crystal, the internal transistor's bias is increased by adding an external resistor from Pin 23 to VEE. -10 dBm of local oscillator drive is needed to adequately drive the mixer (Figure 10). The oscillator configurations specified above, and two others using an external transistor, are described in the application section: 1) A 133 MHz oscillator multiplier using a 3rd overtone 1) crystal, and 2) A 307.8 to 309.3 MHz manually tuned, varactor controlled 2) local oscillator. RSSI The Received Signal Strength Indicator (RSSI) output is a current proportional to the log of the received signal MOTOROLA RF/IF DEVICE DATA amplitude. The RSSI current output is derived by summing the currents from the IF and limiting amplifier stages. An external resistor at Pin 20 sets the voltage range or swing of the RSSI output voltage. Linearity of the RSSI is optimized by using external ceramic or crystal bandpass filters which have an insertion loss of 8.0 dB. The RSSI circuit is designed to provide 70+ dB of dynamic range with temperature compensation (see Figures 6 and 7 which show RSSI responses of the IF and Limiter amplifiers). Variation in the RSSI output current with supply voltage is small (see Figure 11). Carrier Detect When the meter current flowing through the meter load resistance reaches 1.2 Vdc above ground, the comparator flips, causing the carrier detect output to go high. Hysteresis can be accomplished by adding a very large resistor for positive feedback between the output and the input of the comparator. 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 39 dB at 10.7 MHz. Figure 5 shows the gain and saturated output response of the IF amplifier over temperature, while Figure 12 shows the IF amplifier gain as a function of the IF frequency. The fixed internal input impedance is 1.4 k. It is designed for applications where a 455 kHz ceramic filter is used and no external output matching is necessary since the filter requires a 1.4 k source and load impedance. For 10.7 MHz ceramic filter applications, an external 430 resistor must be added in parallel to provide the equivalent load impedance of 330 that is required by the filter; however, no external matching is necessary at the input since the mixer output matches the 330 source impedance of the filter. For 455 kHz applications, an external 1.1 k resistor must be added in series with the mixer output to obtain the required matching impedance of 1.4 k of the filter input resistance. Overall RSSI linearity is dependent on having total midband attenuation of 12 dB (6.0 dB insertion loss plus 6.0 dB impedance matching loss) for the filter. The output of the IF amplifier is buffered and the impedance is 290 . 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. The fixed internal input impedance is 1.4 k. The total gain of the limiting amplifier section is approximately 55 dB. This IF limiting amplifier section internally drives the quadrature detector section. 7 MC13156 Figure 10. Mixer IF Output Level versus Local Oscillator Input Level Figure 9. Mixer Gain versus IF Frequency -5.0 MIXER IF OUTPUT LEVEL (dBm) 20 MIXER GAIN (dB) 15 VEE = -3.0 Vdc Vin = 1.0 mVrms (-47 dBm) RO = 330 Rin = 50 BW(3.0 dB) = 21.7 MHz fIF = fLO - fRF fLO = 150 MHz VLO = 100 mVrms 10 5.0 0 -5.0 0.1 1.0 10 VEE = -3.0 Vdc TA = 25C -10 -15 -20 -25 -30 fRF = 140 MHz; fLO = 150 MHz RF Input Level = -27 dBm (10 mVrms) Rin = 50 ; RO = 330 -35 -40 -45 -50 100 -40 -30 fIF, IF FREQUENCY (MHz) Figure 11. RSSI Output Current versus Supply Voltage and RF Input Signal Level 15 10 TA = 25C 50 IF AMPLIFIER GAIN (dB) I 20 , RSSI OUTPUT CURRENT ( A) Vin = -20 dBm 20 0 Figure 12. IF Amplifier Gain versus IF Frequency 30 25 -10 60 40 35 -20 LO DRIVE (dBm) -40 dBm -60 dBm -80 dBm 10 -100 dBm 2.0 30 Vin = 100 V Rin = 50 RO = 330 BW(3.0 dB) = 26.8 MHz TA = 25C 20 10 5.0 0 1.0 40 3.0 4.0 5.0 6.0 0 0.1 7.0 1.0 VEE, SUPPLY VOLTAGE (-Vdc) 10 100 f, FREQUENCY (MHz) V 14 , RECOVERED AUDIO OUTPUT (mVrms) Figure 13. Recovered Audio Output Voltage versus Supply Voltage 400 300 200 fmod = 1.0 kHz fdev = 75 kHz fRF = 140 MHz RF Input Level = 1.0 mVrms TA = 25C 100 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 VEE, SUPPLY VOLTAGE (-Vdc) 8 MOTOROLA RF/IF DEVICE DATA MC13156 Quadrature Detector The quadrature detector is a doubly balanced four quadrant multiplier with an internal 5.0 pF quadrature capacitor to couple the IF signal to the external parallel RLC resonant circuit that provides the 90 degree phase shift and drives the quadrature detector. A single pin (Pin 13) provides for the external LC parallel resonant network and the internal connection to the quadrature detector. The bandwidth of the detector allows for recovery of relatively high data rate modulation. The recovered signal is converted from differential to single ended through a push-pull NPN/PNP output stage. Variation in recovered audio output voltage with supply voltage is very small (see Figure 13). The output drive capability is approximately 9.0 A for a frequency deviation of 75 kHz and 1.0 kHz modulating frequency (see Application Circuit). Data Slicer The data slicer input (Pin 15) is self centering around 1.1 V with clamping occurring at 1.1 0.5 Vbe Vdc. It is designed to square up the data signal. Figure 14 shows a detailed schematic of the data slicer. The Voltage Regulator sets up 1.1 Vdc on the base of Q12, the Differential Input Amplifier. There is a potential of 1.0 Vbe on the base-collector of transistor diode Q11 and 2.0 Vbe on the base-collector of Q10. This sets up a 1.5 Vbe (~ 1.1 Vdc) on the node between the 36 k resistors which is connected to the base of Q12. The differential output of the data slicer Q12 and Q13 is converted to a single-ended output by the Driver Circuit. Additional circuitry, not shown in Figure 14, tends to keep the data slicer input centered at 1.1 Vdc as input signal levels vary. The Input Diode Clamp Circuit provides the clamping at 1.0 Vbe (0.75 Vdc) and 2.0 Vbe (1.45 Vdc). Transistor diodes Q7 and Q8 are on, thus, providing a 2.0 Vbe potential at the base of Q1. Also, the voltage regulator circuit provides a potential of 2.0 Vbe on the base of Q3 and 1.0 Vbe on the emitter of Q3 and Q2. When the data slicer input (Pin 15) is MOTOROLA RF/IF DEVICE DATA pulled up, Q1 turns off; Q2 turns on, thereby clamping the input at 2.0 Vbe. On the other hand, when Pin 15 is pulled down, Q1 turns on; Q2 turns off, thereby clamping the input at 1.0 Vbe. The recovered data signal from the quadrature detector is ac coupled to the data slicer via an input coupling capacitor. The size of this capacitor and the nature of the data signal determine how faithfully the data slicer shapes up the recovered signal. The time constant is short for large peak to peak voltage swings or when there is a change in dc level at the detector output. For small signal or for continuous bits of the same polarity which drift close to the threshold voltage, the time constant is longer. When centered there is no input current allowed, which is to say, that the input looks high in impedance. Another unique feature of the data slicer is that it responds to various logic levels applied to the Data Slicer Hold Control pin (Pin 18). Figure 15 illustrates how the input and output currents under "no hold" condition relate to the input voltage. Figure 16 shows how the input current and input voltage relate for both the "no hold" and "hold" condition. The hold control (Pin18) does three separate tasks: 1) With Pin 18 at 1.0 Vbe or greater, the output is shut off (sets high). Q19 turns on which shunts the base drive from Q20, thereby turning the output off. 2) With Pin 18 at 2.0 Vbe or greater, internal clamping diodes are open circuited and the comparator input is shut off and effectively open circuited. This is accomplished by turning off the current source to emitters of the input differential amplifier, thus, the input differential amplifier is shut off. 3) When the input is shut off, it allows the input capacitor to hold its charge during transmit to improve recovery at the beginning of the next receive period. When it is turned on, it allows for very fast charging of the input capacitor for quick recovery of new tuning or data average. The above features are very desirable in a TDD digital FM system. 9 MC13156 Figure 14. Data Slicer Circuit 9 15 VCC DS In 8.0 k 8.0 k Data Out 17 Q15 Q14 Q10 Q3 36 k Q20 Q1 Q12 Q5 Q13 36 k Q7 Q2 Q8 16 DS Gnd 32 k Q4 Q18 Q6 Q11 Q9 Q19 Q17 Q16 64 k 16 k VEE 16 k 64 k 64 k 19 Input Diode Clamp Circuit (Q1 to Q9) Voltage Regulator (Q10, Q11) Differential Input Amplifier (Q12, Q13) Figure 15. Data Slicer Input/Output Currents versus Input Voltage 0.1 0.5 -0.1 -0.5 -0.3 -0.5 0.6 Input Current (I15) 0.8 1.0 VEE = -3.0 Vdc V18 = 0 Vdc (No Hold) 1.2 1.4 V15, INPUT VOLTAGE (Vdc) 10 1.6 -1.5 VEE = -3.0 Vdc I 15 , INPUT CURRENT ( A) 1.5 Output Current (I17) 150 I 17 , OUTPUT CURRENT (mA) I 15 , INPUT CURRENT (mA) 0.3 18 DS Hold Figure 16. Data Slicer Input Current versus Input Voltage 2.5 0.5 Driver and Output Circuit (Q14, Q20) 100 50 0 -50 No Hold Hold -2.5 1.8 Hold V18 1O No Hold V18 = 0 Vdc -100 -1.0 -0.5 0 0.5 1.0 1.5 2.0 2.5 3.0 V15, INPUT VOLTAGE (Vdc) MOTOROLA RF/IF DEVICE DATA MC13156 Figure 17. MC13156DW Application Circuit + 1.0 (6) 0.146 MMBR5179 15 k 100 p MC13156 7.5 p 144.455 MHz RF Input 68 p 50 p Mixer 1 (1) 0.1 SMA (5) 0.82 24 5.6 k 470 43 p 133.755 MHz Osc/Tripler 23 2 10 n (4) 3rd O.T. XTAL 1.0 k 10 n 3 (2) 10.7 MHz Ceramic Filter 4 22 VEE VCC 21 Bias 100 k 5 10 n 47 k IF Amp 6 VEE 430 19 10 n Data Slicer Hold 18 7 Data Slicer 10 k Bias 8 VCC RSSI Output 20 10 n 10 n Carrier Detect 17 Data Output (2) 10.7 MHz Ceramic Filter 9 10 VCC VEE LIM Amp 16 100 n 15 180 p 10 n 100 k 11 14 100 k 430 10 n 13 12 5.0 p 150 p + 10 k (3) 1.5 VCC 1.0 NOTES: 1. 0.1 H Variable Shielded Inductor: Coilcraft part # M1283-A or equivalent. 2. 10.7 MHz Ceramic Filter: Toko part # SK107M5-A0-10X or Murata Erie part # SFE10.7MHY-A. 3. 1.5 H Variable Shielded Inductor: Toko part # 292SNS-T1373. 4. 3rd Overtone, Series Resonant, 25 PPM Crystal at 44.585 MHz. 5. 0.814 H Variable Shielded Inductor: Coilcraft part # 143-18J12S. 6. 0.146 H Variable Inductor: Coilcraft part # 146-04J08. MOTOROLA RF/IF DEVICE DATA 11 MC13156 APPLICATIONS INFORMATION Component Selection The evaluation PC board is designed to accommodate specific components, while also being versatile enough to use components from various manufacturers and coil types. Figures NO TAG and NO TAG show the placement for the components specified in the application circuit (Figure 17). The applications circuit schematic specifies particular components that were used to achieve the results shown in the typical curves and tables but equivalent components should give similar results. Input Matching Networks/Components The input matching circuit shown in the application circuit schematic is passive high pass network which offers effective image rejection when the local oscillator is below the RF input frequency. Silver mica capacitors are used for their high Q and tight tolerance. The PC board is not dedicated to any particular input matching network topology; space is provided for the designer to breadboard as desired. Alternate matching networks using 4:1 surface mount transformers or BALUNS provide satisfactory performance. The 12 dB SINAD sensitivity using the above matching networks is typically -100 dBm for fmod = 1.0 kHz and fdev = 75 kHz at fIN = 144.45 MHz and fOSC = 133.75 MHz (see Figure 23). It is desirable to use a SAW filter before the mixer to provide additional selectivity and adjacent channel rejection and improved sensitivity. The SAW filter should be designed to interface with the mixer input impedance of approximately 1.0 k. Table 1 displays the series equivalent single-ended mixer input impedance. Local Oscillators VHF Applications - The local oscillator circuit shown in the application schematic utilizes a third overtone crystal and an RF transistor. Selecting a transistor having good phase noise performance is important; a mandatory criteria is for the device to have good linearity of beta over several decades of collector current. In other words, if the low current beta is suppressed, it will not offer good 1/f noise performance. A third overtone series resonant crystal having at least 25 ppm tolerance over the operating temperature is recommended. The local oscillator is an impedance inversion third overtone Colpitts network and harmonic generator. In this circuit a 560 to 1.0 k resistor shunts the crystal to ensure that it operates in its overtone mode; thus, a blocking capacitor is needed to eliminate the dc path to ground. The resulting parallel LC network should "free-run" near the crystal frequency if a short to ground is placed across the crystal. To provide sufficient output loading at the collector, a high Q variable inductor is used that is tuned to self resonate at the 3rd harmonic of the overtone crystal frequency. The on-chip grounded collector transistor may be used for HF and VHF local oscillator with higher order overtone crystals. Figure 18 shows a 5th overtone oscillator at 93.3 MHz and Figure 19 shows a 7th overtone oscillator at 148.3 MHz. Both circuits use a Butler overtone oscillator configuration. The amplifier is an emitter follower. The crystal is driven from the emitter and is coupled to the high impedance base through a capacitive tap network. Operation at the desired overtone frequency is ensured by the parallel resonant circuit formed by the variable inductor and the tap capacitors and parasitic capacitances of the on-chip transistor and PC board. The variable inductor specified in the schematic could be replaced with a high tolerance, high Q ceramic or air wound surface mount component if the other components have good tolerances. A variable inductor provides an adjustment for gain and frequency of the resonant tank ensuring lock up and startup of the crystal oscillator. The overtone crystal is chosen with ESR of typically 80 and 120 maximum; if the resistive loss in the crystal is too high, the performance of the oscillator may be impacted by lower gain margins. Table 1. Mixer Input Impedance Data (Single-ended configuration, VCC = 3.0 Vdc, local oscillator drive = 100 mVrms) 12 Frequency (MHz) Series Equivalent Complex Impedance (R + jX) () Parallel Resistance Rp () Parallel Capacitance Cp (pF) 90 190 - j380 950 4.7 100 160 - j360 970 4.4 110 130 - j340 1020 4.2 120 110 - j320 1040 4.2 130 97 - j300 1030 4.0 140 82 - j280 1040 4.0 150 71 - j270 1100 4.0 160 59 - j260 1200 3.9 170 52 - j240 1160 3.9 180 44 - j230 1250 3.8 190 38 - j220 1300 3.8 MOTOROLA RF/IF DEVICE DATA MC13156 A series LC network to ground (which is VCC) is comprised of the inductance of the base lead of the on-chip transistor and PC board traces and tap capacitors. Parasitic oscillations often occur in the 200 to 800 MHz range. A small resistor is placed in series with the base (Pin 24) to cancel the negative resistance associated with this undesired mode of oscillation. Since the base input impedance is so large a small resistor in the range of 27 to 68 has very little effect on the desired Butler mode of oscillation. The crystal parallel capacitance, Co, provides a feedback path that is low enough in reactance at frequencies of 5th overtone or higher to cause trouble. Co has little effect near resonance because of the low impedance of the crystal motional arm (Rm-Lm-Cm). As the tunable inductor which forms the resonant tank with the tap capacitors is tuned off the crystal resonant frequency, it may be difficult to tell if the oscillation is under crystal control. Frequency jumps may occur as the inductor is tuned. In order to eliminate this behavior an inductor (Lo) is placed in parallel with the crystal. Lo is chosen to resonant with the crystal parallel capacitance (Co) at the desired operation frequency. The inductor provides a feedback path at frequencies well below resonance; however, the parallel tank network of the tap capacitors and tunable inductor prevent oscillation at these frequencies. UHF Application Figure 20 shows a 318.5 to 320 MHz receiver which drives the mixer with an external varactor controlled (307.8 to 309.3 MHz) LC oscillator using an MPS901 (RF low power transistor in a TO-92 plastic package; also MMBR901 is available in a SOT-23 surface mount package). With the 50 k 10 turn potentiometer this oscillator is tunable over a range of approximately 1.5 MHz. The MMBV909L is a low voltage varactor suitable for UHF applications; it is a dual back-to-back varactor in a SOT-23 package. The input matching networ k us es a 1:4 impedanc e matching transformer (Recommended sources are Mini-Circuits and Coilcraft). Using the same IF ceramic filters and quadrature detector circuit as specified in the applications circuit in Figure 17, the 12 dB SINAD performance is -95 dBm for a fmod = 1.0 kHz sinusoidal waveform and fdev 40 kHz. This circuit is breadboarded using the evaluation PC board shown in Figures NO TAG and NO TAG. The RF ground is VCC and path lengths are minimized. High quality surface mount components were used except where specified. The absolute values of the components used will vary with layout placement and component parasitics. RSSI Response Figure 24 shows the full RSSI response in the application circuit. The 10.7 MHz, 110 kHz wide bandpass ceramic filters (recommended sources are TOKO part # SK107M5-AO-10X or Murata Erie SFE10.7MHY-A) provide the correct bandpass insertion loss to linearize the curve between the limiter and IF portions of RSSI. Figure 23 shows that limiting occurs at an input of -100 dBm. As shown in Figure 24, the RSSI output linear from -100 dBm to -30 dBm. The RSSI rise and fall times for various RF input signal levels and R20 values are measured at Pin 20 without 10 nF filter capacitor. A 10 kHz square wave pulses the RF input signal on and off. Figure 25 shows that the rise and fall times are short enough to recover greater than 10 kHz ASK data; with a wider IF bandpass filters data rates up to 50 kHz may be achieved. The circuit used is the application circuit in Figure 17 with no RSSI output filter capacitor. Figure 18. MC13156DW Application Circuit fRF = 104 MHz; fLO = 93.30 MHz 5th Overtone Crystal Oscillator (4) 0.135 H 33 (2) 10 p 104 MHz SMA Mixer 120 p RF Input 27 p 1 24 2 23 (1) 0.1 3.0 p 1.0 H (3) 10 n 4.7 k 3 + 1.0 VEE 30 p 5th OT XTAL 22 10 n To Filter VCC NOTES: 1. 0.1 H Variable Shielded Inductor: Coilcraft part # M1283-A or equivalent. 2. Capacitors are Silver Mica. 3. 5th Overtone, Series Resonant, 25 PPM Crystal at 93.300 MHz. 4. 0.135 H Variable Shielded Inductor: Coilcraft part # 146-05J08S or equivalent. MOTOROLA RF/IF DEVICE DATA 13 MC13156 Figure 19. MC13156DW Application Circuit fRF = 159 MHz; fLO = 148.30 MHz 7th Overtone Crystal Oscillator (4) 76 nH + 1.0 33 (2) 5.0 p 159 MHz RF Input (1) 0.08 H SMA 27 p Mixer 50 p 1 24 2 23 3 22 0.22 H 47 p 10 n 4.7 k 470 VEE (3) 7th OT XTAL 10 n VCC To IF Filter NOTES: 1. 0.08 H Variable Shielded Inductor: Toko part # 292SNS-T1365Z or equivalent. 2. Capacitors are Silver Mica. 3. 7th Overtone, Series Resonant, 25 PPM Crystal at 148.300 MHz. 4. 76 nH Variable Shielded Inductor: Coilcraft part # 150-03J08S or equivalent. Figure 20. MC13156DW Varactor Controlled LC Oscillator 4.7 k MPS901 (1) 1:4 Transformer 6.8 p 47 k VVCO + 1.0 (6) 318.5 to 320 MHz RF Input (2) 50 k 1.0 M 0.1 Mixer 1 24 2 23 24 p 20 p (4) MMBV909L SMA 12 k 24 p (3) 18.5 nH 1.8 k 3 VEE 22 1.0 n 307.8-309.3 MHz LC Varactor Controlled Oscillator VCC = 3.3 Vdc (Reg) NOTES: 1. 1:4 Impedance Transformer: Mini-Circuits. 2. 50 k Potentiometer, 10 turns. 3. Spring Coil; Coilcraft A05T. 4. Dual Varactor in SOT-23 Package. 5. All other components are surface mount components. 6. Ferrite beads through loop of 24 AWG wire. 14 MOTOROLA RF/IF DEVICE DATA MC13156 The 12 dB SINAD performance is -109 dBm for a fmod = 1.0 kHz and a fdev = 4.0 kHz. The RSSI dynamic range is approximately 80 dB of linear range (see Figure 22). 45 MHz Narrowband Receiver The above application examples utilize a 10.7 MHz IF. In this section a narrowband receiver with a 455 kHz IF will be described. Figure 21 shows a full schematic of a 45 MHz receiver that uses a 3rd overtone crystal with the on-chip oscillator transistor. The oscillator configuration is similar to the one used in Figure 17; it is called an impedance inversion Colpitts. A 44.545 MHz 3rd overtone, series resonant crystal is used to achieve an IF frequency at 455 kHz. The ceramic IF filters selected are Murata Erie part # SFG455A3. 1.2 k chip resistors are used in series with the filters to achieve the terminating resistance of 1.4 k to the filter. The IF decoupling is very important; 0.1 F chip capacitors are used at Pins 6, 7, 11 and 12. The quadrature detector tank circuit uses a 455 kHz quadrature tank from Toko. Receiver Design Considerations The curves of signal levels at various portions of the application receiver with respect to RF input level are shown in Figure 26. This information helps determine the network topology and gain blocks required ahead of the MC13156 to achieve the desired sensitivity and dynamic range of the receiver system. In the application circuit the input third order intercept (IP3) performance of the system is approximately -25 dBm (see Figure 27). Figure 21. MC13156DW Application Circuit at 45 MHz 1.8 H + 1.0 (6) 33 p 45 Hz RF Input SMA (1) 0.33 H 10 n Mixer 1 24 56 p 10 n 470 k 23 2 39 p 1.2 k 3 (2) 455 kHz Ceramic Filter 4 VCC 10 k 10 n 21 Bias RSSI Output 10 n 47 k IF Amp 6 VEE 0.1 19 10 n Data Slicer Hold 18 7 Data Slicer 1.2 k 10 k 17 Bias 8 Carrier Detect 100 k 20 0.1 (4) 3rd OT XTAL 44.545 MHz 22 VEE 5 VCC (5) 0.416 H 180 p Data Output (2) 455 kHz Ceramic Filter 9 VCC VEE 100 n 15 10 0.1 16 LIM Amp 100 k 14 11 1.0 n 0.1 Audio To C-Message Filter and Amp. 100 k 13 12 5.0 p 27 k NOTES: 1. 0.33 H Variable Shielded Inductor: Coilcraft part # 7M3-331 or equivalent. 2. 455 kHz Ceramic Filter: Murata Erie part # SFG455A3. 3. 455 kHz Quadrature Tank: Toko part # 7MC8128Z. 4. 3rd Overtone, Series Resonant, 25 PPM Crystal at 44.540 MHz. 5. 0.416 H Variable Shielded Inductor: Coilcraft part # 143-10J12S. 6. 1.8 H Molded Inductor. MOTOROLA RF/IF DEVICE DATA + 180 p (3) 680 H VCC = 2.0 to 5.0 Vdc 1.0 15 MC13156 Figure 23. S + N/N versus RF Input Signal Level 1.8 10 1.6 0 1.4 fRF = 45.00 MHz VCC = 2.0 Vdc 12 dB SINAD @ -109 dBm (0.8 Vrms) (See Figure 21) 1.2 1.0 S + N, N (dB) RSSI OUTPUT VOLTAGE (Vdc) Figure 22. RSSI Output Voltage versus Input Signal Level 0.8 S+N VCC = 5.0 Vdc fdev = 75 kHz fmod = 1.0 kHz fin = 144.45 MHz (See Figure 17) -10 -20 -30 0.6 -40 0.4 -120 -50 -110 -100 N -100 -80 -60 -40 -20 0 20 t r , t f , RSSI RISE AND FALL TIMES ( s) RSSI OUTPUT VOLTAGE (Vdc) 0.8 VCC = 5.0 Vdc fc = 144.455 MHz fLO = 133.755 MHz Low Loss 10.7 MHz Ceramic Filter (See Figure 17) 0.6 0.4 35 30 25 20 15 10 5.0 0 -100 -80 -60 -40 -20 0 0 SIGNAL INPUT LEVEL (dBm) Figure 26. Signal Levels versus RF Input Signal Level -40 -30 -20 E E E E E E CC E CC E CC E E E E E E C E C E C E -20 E E E E E CC E CC E CC E -40 tr tf tr tf tr tf @ 22 k @ 22 k @ 47 k @ 47 k @ 100 k @ 100 k E CC E CC E CC E CC E CC E E CC -60 -80 RF INPUT SIGNAL LEVEL (dBm) 10 LO Level = -2.0 dBm (See Figure 17) MIXER IF OUTPUT LEVEL (dBm) IF Output Limiter Input -20 POWER (dBm) -50 Figure 27. 1.0 dB Compression Pt. and Input Third Order Intercept Pt. versus Input Power 0 -30 -40 -50 -60 -90 -80 -70 -60 -50 RF INPUT SIGNAL LEVEL (dBm) 16 -60 Figure 25. RSSI Output Rise and Fall Times versus RF Input Signal Level 1.0 -70 -100 -70 Figure 24. RSSI Output Voltage versus Input Signal Level 1.2 -10 -80 RF INPUT SIGNAL (dBm) 1.4 0.2 -120 -90 SIGNAL INPUT LEVEL (dBm) -40 -30 0 -10 -20 VCC = 5.0 Vdc fRF1 = 144.4 MHz fRF2 = 144.5 MHz fLO = 133.75 MHz PLO = -2.0 dBm (See Figure 17) 1.0 dB Comp. Pt. = -37 dBm IP3 = -25 dBm -30 -40 -50 -60 -70 -100 -80 -60 -40 -20 0 RF INPUT POWER (dBm) MOTOROLA RF/IF DEVICE DATA MC13156 BER TESTING AND PERFORMANCE * Data rate = 100 kbps * Filter cutoff frequency set to 39% of the data rate or 39 kHz. * Filter type is a 5 pole equal-ripple with 0.5 phase error. * VCC = 4.0 Vdc * Frequency deviation = 32 kHz. MOTOROLA RF/IF DEVICE DATA 10 -1 BER, BIT ERROR RATE Description The test setup shown in Figure 29 is configured so that the function generator supplies a 100 kHz clock source to the bit error rate tester. This device generates and receives a repeating data pattern and drives a 5 pole baseband data filter. The filter effectively reduces harmonic content of the baseband data which is used to modulate the RF generator which is running at 144.45 MHz. Following processing of the signal by the receiver (MC13156), the recovered baseband sinewave (data) is AC coupled to the data slicer. The data slicer is essentially an auto-threshold comparator which tracks the zero crossing of the incoming sinewave and provides logic level data at its ouput. Data errors associated with the recovered data are collected by the bit error rate receiver and displayed. Bit error rate versus RF signal input level and IF filter bandwidth are shown in Figure 28. The bit error rate data was taken under the following test conditions: 10 -3 Figure 28. Bit Error Rate versus RF Input Signal Level and IF Bandpass Filter VCC = 4.0 Vdc Data Pattern = 2E09 Prbs NRZ Baseband Filter fc = 50 kHz fdev = 32 kHz IF Filter BW 110 kHz IF Filter BW 230 kHz 10 -5 10 -7 -90 -85 -80 -75 -70 RF INPUT SIGNAL LEVEL (dBm) Evaluation PC Board The evaluation PCB is very versatile and is intended to be used across the entire useful frequency range of this device. The center section of the board provides an area for attaching all SMT components to the circuit side and radial leaded components to the component ground side (see Figures NO TAG and NO TAG). Additionally, the peripheral area surrounding the RF core provides pads to add supporting and interface circuitry as a particular application dictates. 17 MC13156 Figure 29. Bit Error Rate Test Setup Function Generator Bit Error Rate Tester RF Generator Wavetek Model No. 164 HP3780A or Equivalent HP8640B Clock Out Gen Clock Input Rcr Clock Input Rcr Data Input Generator Input Modulation Input RF Output 5 Pole Bandpass Filter Data Slicer Output Mixer Input MC13156 UUT 18 MOTOROLA RF/IF DEVICE DATA MC13156 OUTLINE DIMENSIONS FB SUFFIX PLASTIC QFP PACKAGE CASE 873-01 ISSUE A L 0.20 (0.008) D S H A-B V M B 0.20 (0.008) L 0.05 (0.002) A-B -B- -A- M C A-B S D S 16 S 17 24 25 B 32 P B DETAIL A 9 1 8 -A-, -B-, -D- -D- DETAIL A A 0.20 (0.008) M C A-B D S S 0.05 (0.002) A-B S 0.20 (0.008) M H A-B S D F BASE METAL S M DETAIL C N J C E -H- -C- SEATING PLANE H M G 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 RF/IF 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 6.95 7.10 6.95 7.10 1.40 1.60 0.273 0.373 1.30 1.50 0.273 --- 0.80 BSC --- 0.20 0.119 0.197 0.33 0.57 5.6 REF 6_ 8_ 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 1.00 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 6_ 8_ 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 19 MC13156 OUTLINE DIMENSIONS DW SUFFIX PLASTIC PACKAGE CASE 751E-04 (SO-24L) ISSUE E -A- 24 NOTES: 1. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. 2. CONTROLLING DIMENSION: MILLIMETER. 3. DIMENSIONS A AND B DO NOT INCLUDE MOLD PROTRUSION. 4. MAXIMUM MOLD PROTRUSION 0.15 (0.006) PER SIDE. 5. DIMENSION D DOES NOT INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL BE 0.13 (0.005) TOTAL IN EXCESS OF D DIMENSION AT MAXIMUM MATERIAL CONDITION. 13 -B- 12X P 0.010 (0.25) 1 M B M 12 24X D J 0.010 (0.25) M T A S B S F R C -T- SEATING PLANE M 22X G K X 45 _ DIM A B C D F G J K M P R MILLIMETERS MIN MAX 15.25 15.54 7.40 7.60 2.35 2.65 0.35 0.49 0.41 0.90 1.27 BSC 0.23 0.32 0.13 0.29 0_ 8_ 10.05 10.55 0.25 0.75 INCHES MIN MAX 0.601 0.612 0.292 0.299 0.093 0.104 0.014 0.019 0.016 0.035 0.050 BSC 0.009 0.013 0.005 0.011 0_ 8_ 0.395 0.415 0.010 0.029 Motorola reserves the right to make changes without further notice to any products herein. Motorola makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Motorola assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. "Typical" parameters which may be provided in Motorola data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be validated for each customer application by customer's technical experts. Motorola does not convey any license under its patent rights nor the rights of others. Motorola products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Motorola product could create a situation where personal injury or death may occur. Should Buyer purchase or use Motorola products for any such unintended or unauthorized application, Buyer shall indemnify and hold Motorola and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Motorola was negligent regarding the design or manufacture of the part. Motorola and are registered trademarks of Motorola, Inc. Motorola, Inc. is an Equal Opportunity/Affirmative Action Employer. Mfax is a trademark of Motorola, Inc. How to reach us: USA / EUROPE / Locations Not Listed: Motorola Literature Distribution; P.O. Box 5405, Denver, Colorado 80217. 1-303-675-2140 or 1-800-441-2447 JAPAN: Nippon Motorola Ltd.: SPD, Strategic Planning Office, 141, 4-32-1 Nishi-Gotanda, Shagawa-ku, Tokyo, Japan. 03-5487-8488 Customer Focus Center: 1-800-521-6274 Mfax: RMFAX0@email.sps.mot.com - TOUCHTONE 1-602-244-6609 ASIA/PACIFIC: Motorola Semiconductors H.K. Ltd.; 8B Tai Ping Industrial Park, Motorola Fax Back System - US & Canada ONLY 1-800-774-1848 51 Ting Kok Road, Tai Po, N.T., Hong Kong. 852-26629298 - http://sps.motorola.com/mfax/ HOME PAGE: http://motorola.com/sps/ 20 MC13156/D MOTOROLA RF/IF DEVICE DATA