LA1781M

Ordering number : EN6038A Monolithic Linear IC LA1781M Overview For Car Radios Single-Chip Tuner IC The LA1781M integrates all six blocks required in a car radio tuner on a single chip. Features • Improved noise reduction methods The FM front end provides excellent 3-signal characteristics equivalent to those of the LA1193M. Superlative listenability due to improved medium and weak field noise canceller characteristics. Improved separation characteristics. Anti-birdie filter. Improved AM and FM thermal characteristics. Excellent FM signal meter linearity. Modified N.C. circuit for improved noise rejection. • Double conversion AM tuner (up conversion) Reduces the number of external components required as compared to earlier double conversion tuners, in particular, no crystal is required (when used in conjunction with the LC72144). • Sample-to-sample variation reduction circuit built into the FM IF circuit. (Fixed resistors are used for the SD, keyed AGC, mute on adjustment, ATT, SNC, and HCC functions.) • The LA1781 inherits the block arrangement of the LA1780M and supports pin-compatible designs. Functions • FM front end • Multiplex • FM IF • AM up-conversion • Noise canceller • FM/AM switch • MRC Any and all SANYO Semiconductor Co.,Ltd. products described or contained herein are, with regard to "standard application", intended for the use as general electronics equipment (home appliances, AV equipment, communication device, office equipment, industrial equipment etc.). The products mentioned herein shall not be intended for use for any "special application" (medical equipment whose purpose is to sustain life, aerospace instrument, nuclear control device, burning appliances, transportation machine, traffic signal system, safety equipment etc.) that shall require extremely high level of reliability and can directly threaten human lives in case of failure or malfunction of the product or may cause harm to human bodies, nor shall they grant any guarantee thereof. If you should intend to use our products for applications outside the standard applications of our customer who is considering such use and/or outside the scope of our intended standard applications, please consult with us prior to the intended use. If there is no consultation or inquiry before the intended use, our customer shall be solely responsible for the use. Specifications of any and all SANYO Semiconductor Co.,Ltd. products described or contained herein stipulate the performance, characteristics, and functions of the described products in the independent state, and are not guarantees of the performance, characteristics, and functions of the described products as mounted in the customer' s products or equipment. To verify symptoms and states that cannot be evaluated in an independent device, the customer should always evaluate and test devices mounted in the customer' s products or equipment. 71509 SY PC/32301TN (OT) No.6038-1/48 LA1781M Specifications Maximum Ratings at Ta = 25°C Parameter Maximum supply voltage Symbol VCC1 max VCC2 max Allowable power dissipation Operating temperature Storage temperature Pd max Topr Tstg Pins 6, 40, and 61 Pins 7, 45, 54, 59, and 60 Ta ≤ 55°C Conditions Ratings 9 12 950 -40 to +85 -40 to +150 Unit V V mW °C °C Operating Conditions at Ta = 25°C Parameter Recommended supply voltage Symbol VCC VCCST IND Operating supply voltage range VCC op Conditions Pins 6, 7, 40, 45, 54, 59, 60, and 61 Pin 26 Ratings 8 5 7.5 to 9.0 Unit V V V Electrical Characteristics at Ta = 25°C, VCC = 8V, in the specified test circuit for the FM IF input Parameter Symbol Conditions min FM characteristics At the FM IF input Current drain Demodulation output Pin 31 demodulation output Channel balance Total harmonic distortion Signal-to-noise ratio : IF AM suppression ratio: IF Muting attenuation ICCO-FM VO-FM VO-FM31 CB THD-FM mono S/N-FM IF AMR IF Att-1 Att-2 Att-3 Separation Stereo on level Stereo off level Main total harmonic distortion Pilot cancellation SNC output attenuation HCC output attenuation Sep ST-ON ST-OFF THD-Main L PCAN AttSNC AttHCC-1 AttHCC-2 Input limiting voltage Muting sensitivity SD sensitivity VIN-LIM VIN-MUTE SD-sen1 FM SD-sen2 FM IF counter buffer output Signal meter output VIFBUFF-FM VSMFM-1 VSMFM-2 VSMFM-3 VSMFM-4 Muting bandwidth Mute drive output BW-MUTE VMUTE-100 10.7MHz, 100dBμ, unmodulated. The pin 23 output No input. The pin 24 DC output, unmodulated 50dBμ. The pin 24 DC output, unmodulated 70dBμ. The pin 24 DC output, unmodulated 100dBμ. The pin 24 DC output, unmodulated 100dBμ. The bandwidth when V33 = 2V, unmodulated 100dBμ, 0dBμ. The pin 33 DC output, unmodulated No input, I40 + I45 + I54 + I59 + I60 + I61 10.7MHz, 100dBμ, 1kHz, 100%mod, The pin 15 output 10.7MHz, 100dBμ, 1kHz, 100%mod, The pin 31 output The ratio between pins 15 and 16 at 10.7MHz, 100dBμ, 1kHz 10.7MHz, 100dBμ, 1kHz, 100% mod, pin 15 10.7MHz, 100dBμ, 1kHz, 100% mod, pin 15 10.7MHz, 100dBμ, 1kHz, fm = 1kHz, 30% AM, pin 15 10.7MHz, 100 dBμ, 1kHz. The pin 15 attenuation when V33 goes from 0 to 2V 10.7MHz, 100 dBμ, 1kHz. The pin 15 attenuation when V33 goes from 0 to 2V*1 10.7MHz, 100 dBμ, 1kHz. The pin 15 attenuation when V33 goes from 0 to 2V*2 10.7MHz, 100dBμ, L + R = 90%, pilot = 10%. The pin 15 output ratio The pilot modulation such that V26 < 0.5V The pilot modulation such that V26 > 3.5V 10.7MHz, 100dBμ, L + R = 90%, pilot = 10%. The pin 15 signal 10.7MHz, 100dBμ, pilot = 10%. The pin 15 signal/the pilot level leakage. DIN audio 10.7MHz, 100dBμ, L - R = 90%, pilot = 10%. V28 = 3V → 0.6V, pin 15 10.7MHz, 100dBμ, 10kHz, L + R = 90%, pilot = 10%. V29 = 3V → 0.6V, pin 15 10.7MHz, 100dBμ, 10kHz, L + R = 90%, pilot = 10%. V29 = 3V → 0.1V, pin 15 100dBμ, 10.7MHz, 30% modulation. The IF input such that the input reference output goes down by 3dB The IF input level (unmodulated) when V33 = 2V The IF input level (unmodulated) (over 100mV rms) such that the IF counter buffer output goes on 20 1 0.5 6 33 27 54 54 130 0.0 0.4 2.0 4.7 150 0.00 2.1 1.2 4.1 3.1 0.3 30 5 4.5 10 40 35 62 62 200 0.1 1.0 2.7 5.5 220 0.03 9 8.5 14 47 43 70 70 270 0.3 1.5 3.5 6.2 290 0.20 1.2 6.5 % % % dB dB dB dB dBμ dBμ dBμ dBμ mVrms V V V V kHz V 75 55 5 15 28 30 60 205 190 -1 94 310 295 0 0.3 82 68 10 20 33 40 15 25 38 110 415 380 +1 1.0 mA mVrms mVrms dB % dB dB dB dB dB dB Ratings typ max Unit Continued on next page. No.6038-2/48 LA1781M Continued from preceding page. Parameter FM FE Mixer input N-AGC on input W-AGC on input Conversion gain Oscillator buffer output NC Block NC input (pin 30) Gate time Noise sensitivity NC effect TGATE SN SN-NC f = 1kHz, for a 1μs, 100-mVp-o pulse The level of a 1kHz, 1μs pulse input that starts noise canceller operation. Measured at pin 30. The pulse rejection effect provided by the noise canceller. For a repeated 1μs wide pulse, frequency = 10kHz, 150mVp-o. The ratio of the FM mode pin 15 output referenced to the AM mode pin 15 output (effective value) Multipath rejection circuit MRC input (pin 27) MRC output MRC operating level VMRC MRC-ON V24 = 5V The pin 32 input level at f = 70kHz such that pin 24 goes to 5V and pin 27 goes to 2V 2.2 10 2.3 15 2.4 20 V mVrms 5 55 40 μs mVp-o VNAGC VWAGC A. V VOSCBUFF-FM 83MHz, unmodulated. The input such that the pin 2 voltage is 2.0V or below 83MHz, unmodulated. The input such that the pin 2 voltage is 2.0V or below. (When the keyed AGC is set to 4.0V.) 83MHz, 80dBμ, unmodulated. The FE CF output No input 81 104 19 85 88 110 30 110 95 116 48 165 dBμ dBμ mVrms mVrms Symbol Conditions min Ratings typ max Unit AM characteristics AM ANT input Practical sensitivity Detector output Pin 31 detector output AGC F.O.M. Signal-to-noise ratio Total harmonic distortion Signal meter output S/N-30 VO-AM VO-AM31 VAGC-FOM S/N-AM THD-AM VSMAM-1 VSMAM-2 Oscillator buffer output Wide band AGC sensitivity 1MHz, 30dBμ, fm = 1kHz, 30% modulation, pin 15 1MHz, 74dBμ, fm = 1kHz, 30% modulation, pin 15 1MHz, 74dBμ, fm = 1kHz, 30% modulation, pin 31 1MHz, 74dBμ, referenced to the output, the input amplitude such that the output falls by 10dB. Pin 15 1MHz, 74dBμ, fm = 1kHz, 30% modulation 1MHz, 74dBμ, fm = 1kHz, 80% modulation No input 1MHz, 130dBμ, unmodulated 0.0 3.5 185 92 83 24 24 200 20 130 110 59 47 195 175 64 52 0.3 0.2 4.4 230 98 89 30 30 290 104 95 36 36 1 0.5 6.1 270 230 69 dB mVrms mVrms dB dB % V V mVrms dBμ dBμ dBμ dBμ mVrms VOSCBUFF-AM1 No input, the pin 15 output W-AGCsen1 W-AGCsen2 1.4MHz, the input when V46 = 0.7V 1.4MHz, the input when V46 = 0.7V (seek mode) 1MHz, the ANT input level such that the IF counter output turns on. SD-sen2AM 1MHz, the ANT input level such that the SD pin goes to the on state. 1MHz, 74dBμ, unmodulated. The pin 23 output SD sensitivity SD-sen1AM IF buffer output VIFBUFF-AM Note : These measurements must be made using the either the IC-51-0644-824 or KS8277 IC socket (manufactured by Yamaichi Electronics). *1. When the resistor between pin 58 and ground is 200kΩ. *2. When the resistor between pin 58 and ground is 30kΩ. No.6038-3/48 LA1781M Package Dimensions unit : mm (typ) 3159A Allowable power dissipation, Pd max -- mW 17.2 14.0 48 49 33 32 1000 950 900 800 700 600 500 400 300 200 100 0 --40 --20 0 20 40 60 80 100 Pd max -- Ta Mounted on a specified board : 40 × 80 × 1.3mm3 glass epoxy board Independent IC 14.0 64 1 0.8 (1.0) (2.7) 17 16 0.35 0.15 17.2 0.8 Ambient temperature, Ta -- °C 3.0max 0.1 SANYO : QIP64E(14X14) Function List 1. FM Front End (Equivalent to the Sanyo LA1193) (1) Double input type double balanced mixer (2) Pin diode drive AGC output (3) MOSFET second gate drive AGC output (4) Keyed AGC adjustment pin (5) Differential IF amplifier (6) Wide band AGC sensitivity setting pin, and narrow band AGC sensitivity setting pin (7) Local oscillator 2. FM IF (1) IF limiter amplifier (2) S-meter output (also used for AM) 6-stage pickup (3) Multipath detection pin (shared FM signal meter) (4) Quadrature detection (5) AF preamplifier (6) AGC output (7) Band muting (8) Weak input muting (9) Soft muting adjustment pin (10) Muting attenuation adjustment pin (11) IF counter buffer output (also used for AM) (12) SD (IF counter buffer on level) adjustment pin (13) SD output (active high) (also used for AM) 3. Noise Canceller (1) High-pass filter (first order) (2) Delay circuit based low-pass filter (fourth order) (3) Noise AGC (4) Pilot signal compensation circuit (5) Noise sensitivity setting pin (6) Function for disabling the noise canceller in AM mode 4. Multiplex Functions (1) Adjustment-free VCO circuit (2) Level follower type pilot canceller circuit (3) HCC (high cut control) (4) Automatic stereo/mono switching (5) VCO oscillation stop function (AM mode) (6) Forced monaural (7) SNC (stereo noise controller) (8) Stereo display pin (9) Anti-birdie filter 5. AM (1) Double balanced mixer (1st, 2nd) (2) IF amplifier (3) Detection (4) RF AGC (narrow/wide) (5) Pin diode drive pin (6) IF AGC (7) Signal meter output (also used for FM) (8) Local oscillator circuits (first and second) (9) Local oscillator buffer output (10) IF counter buffer output (also used by the FM IF) (11) SD (IF counter buffer on level) adjustment pin (12) SD output (active high) (also used for AM) (13) Wide AGC (14) Detection output frequency characteristics adjustment pin (low cut, high deemphasis) (15) AM stereo buffer 6. MRC (multipath noise rejection circuit) 7. AM/FM switching output (linked to the FM VCC) No.6038-4/48 LA1781M Operating Characteristics and Symbols Used in the Test Circuit Diagrams (1) Switches (SW) Switch on = 1, SW off = 0 There are two switches that use signal transfer. 1) SW2 : switches between the mixer input and the IF input. 2) SW4 : switches between noise canceler input and IF output + noise canceler input. (2) Types of SG used PG1 (AC1) AC2 AC3 AC4 AC5 Used for noise canceler testing. A pulse generator and an AF oscillator are required. Used for FM front end testing. Outputs an 83MHz signal. Used for FM IF, noise canceler, and MPX testing. Outputs a 10.7MHz signal. Stereo modulation must be possible. Used for AM testing. Outputs 1 MHz and 1.4MHz signals. Used with the MRC. Can also be used for AF and OSC. (3) Power supply VCC VCC1 VCC2 VCC3 8V 5V 0.1V/0.7V/2V/4V 0.1V/0.6V/2V These levels must be variable. SD, stereo, seek/stop Keyed AGC, Mute ATT HCC, SNC, SASC (MRC) (4) (a) Switches Parameter SW1 SW2 SW3 SW4 SW5 SW6 SW7 SW8 SW9 SW10 AM/FM switching. The FE VCC is supplied to pin 62. FM IF switching. Pin 51/FE output For conversion gain testing For switching between noise canceler input and IF output + noise canceler. High-speed SD SEEK/STOP (IF BUFF ON/OFF) MUTE ATT 200kΩ MUTE ATT 30kΩ For pilot cancellation testing Mute off (pin 33) High-speed SD STOP MUTE 200kΩ MUTE 30kΩ When pilot cancellation is used MUTE OFF Other/purposes Seek (IF buffer output) OFF OFF When pilot cancellation is not used MUTE ON ON FM FE IF OUT (A) Conversion gain measurement (A) AC1 (A) OFF AM AC3 (B) Other/purposes Other/purposes (b) Trimmers (variable resistors) VR1 VR2 Separation adjustment Pilot cancellation adjustment (5) Test Points (a) DC voltages VD1 VD2 VD3 VD4 VD5 VD6 VD7 FM RF AGC voltage AM/FM SD, AM Tweet, FM stereo indicator AM/FM S-meter MRC output Mute drive output AM antenna damping voltage N.C. Gate time Pin 2 Pin 26 Pin 24 Pin 27 Pin 33 Pin 46 Pin 8 (b) AC voltages VA1 VA2 VA3 VA4 VA5 AM/FM OSC Buff First IF output IF counter buffer MPX OUT Left ch MPX OUT Right ch Pin 4 Pin 53 → CF → pin 51 load level (10.7MHz) Pin 23 (10.7MHz/450kHz) Pin 15 (AF) Pin 16 (AF) No.6038-5/48 LA1781M Pin Descriptions Pin No. 1 Pin function Antenna damping drive Pin description An antenna damping current flows when the RF AGC voltage (pin 2) reaches VCC - VD. ANT RF AGC Equivalent circuit VCC Pin 62 1000pF 100Ω 1 1000pF 100Ω 300Ω 2 RF AGC Used to control the FET second gate. VCC FET 2ND GATE 12kΩ 2 DAMPING DRIVER + ANT N AGC DET KEYED AGC W AGC DET VCC 3 4 F.E.GND OSC Oscillator connection. The transistor and capacitors required for the oscillator circuit are integrated on the chip. 4 VCC 25pF VT 2kΩ 20pF 7 AM OSC AM first oscillator. This circuit can oscillator up to the SW band. An ALC circuit is included. 7 VCC ALC Continued on next page. No.6038-6/48 LA1781M Continued from preceding page. Pin No. 8 9 Pin function Noise AGC sensitivity AGC adjustment Pin description After setting up the medium field (about 50dBμ) sensitivity with the noise sensitivity setting pin (pin 8), set the weak field (about 20 to 30dBμ) sensitivity with the AGC adjustment pin (pin 9). 200Ω 3kΩ 3kΩ 15kΩ Equivalent circuit 8 3kΩ 0.01μF 1MΩ 9 + 0.47μF 11 12 Memory circuit connection Recording circuit used during noise canceller operation. 0.01μF 6800pF 3.9kΩ 13 12 VCC 11 Differential amp Gate circuit LPF 13 Pilot input Pin 13 is the PLL circuit input pin. VCC 30kΩ PLL N.C 12 13 0.01μF 14 N.C, MPX, MRC, GND Ground for the N.C., MPX, and MRC circuits. Continued on next page. No.6038-7/48 LA1781M Continued from preceding page. Pin No. 15 16 Pin function MPX output (left) MPX output (right) Pin description Deemphasis 50μs : 0.015μF 75μs : 0.022μF Equivalent circuit VCC 3.3kΩ 3.3kΩ 15 0.015μF 16 0.015μF 17 Pilot canceller signal output Adjustment is required since the pilot signal level varies with the sample-to-sample variations in the IF output level and other parameters. 20kΩ 10kΩ VCC 6.7kΩ 17 0.01μF 100kΩ 18 18 Pilot canceller signal output Pin 18 is the output pin for the pilot canceller signal. VCC 1.5kΩ 17 0.01μF 100kΩ 18 19 Separation adjustment pin Use a trimmer to adjust the subdecoder input level. (The output level is not modified in mono and main modes.) Composit signal 5kΩ DECODER 19 30kΩ 0.047μF Continued on next page. No.6038-8/48 LA1781M Continued from preceding page. Pin No. 20 VCO Pin function Pin description The oscillator frequency is 912Hz. KBR-912F108 (Kyocera Corporation) CSB-912JF108 (Murata Mfg. Co., Ltd.) VREF Equivalent circuit CSB 912 JF104 20 10pF 21 22 PHASE COMP. PHASE COMP. VREF 15kΩ + 15kΩ 19kΩ 21 + + 22 23 IF counter buffer seek/stop switching This pin functions both as the IF counter buffer (AC output) and as the seek/stop switch pin. The voltage V23 switches between the following three modes. During FM reception : 5V : 0V : Seek mode Reception mode AM reception (two modes : 0 and 5V) 5V : 0V : Seek mode Reception mode STOP IF BUFF. Forced SD:2.5V SEEK 5V SD circuit 23 51kΩ SW + -- 4.9V + -- 50kΩ + -- AM MUTE VCC IF counter buffer 1.3V 10kΩ 150Ω 2.5V : Forced SD mode 50F Continued on next page. No.6038-9/48 LA1781M Continued from preceding page. Pin No. 24 Pin function AM/FM signal meter output. 32 Dedicated FM signal meter In AM mode, pin 32 outputs a 1mA current. Thus the HCC circuit is turned off. AM S-meter 10kΩ 10kΩ 24 AM/FM SW FM S-meter 32 Pin description Fixed-current drive signal meter Equivalent circuit VCC Outputs a 1-mA current during AM reception MRC AM/FM SW 26 Stereo indicator for the SD pin The voltage V23 switches between three modes as follows. FM reception : 5V : The SD pin operates linked to the IF counter buffer. 2.5V : Forced SD mode: operates as the SD pin. 0.7V : Reception mode: stereo indicator AM reception : (two modes : 0 and 5V) 5V : 0V : Operates as the seek SD pin. Reception mode. Not used. 100kΩ VDD 26 Seek/stop switching AM/FM SD Stereo indicator 27 MRC control voltage time constant The MRC detector time constant is determined by a 100Ω resistor and C2 when discharging and by the 2μA current and C2 when charging. 2μA VCC VCC 27 100Ω + C2 Pin 28 28 SNC control input The sub-output is controlled by a 0 to 1V input. VREF 28 Continued on next page. No.6038-10/48 LA1781M Continued from preceding page. Pin No. 29 Pin function HCC control input Pin description The high band frequency output is controlled by a 0 to 1V input. It can also be controlled by the MRC output. Use a resistor of at least 100kΩ when controlling with the pin 32 FM S-meter signal. Equivalent circuit VREF 32 29 1μF + 30 Noise canceller input Pin 30 is the noise canceller input. The input impedance is 50kΩ. FM detector output VCC 31 AM/FM detector output Pin 31 is the AM and FM detector output In FM mode, this is a low-impedance output. In AM mode, the output impedance is 10kΩ. To improve the low band separation, use a coupling capacitor of over 10μF. 31 10kΩ VCC AM detector 1μF + 30 Noise canceller 50kΩ 4.2V 32 IF S-meter output and MRC DC input FM S-meter output block MRC AC input block Adjust the external 1kΩ resistor to attenuate the MRC AC input and control the circuit. VCC 32 10kΩ + 1 μF 1kΩ MRC input Continued on next page. No.6038-11/48 LA1781M Continued from preceding page. Pin No. 33 Pin function Mute drive output Pin description •The muting time constant is determined by an external RC circuit as described below. Attack time : TA = 10kΩ × C1 Release time : TR = 50kΩ × C1 •Noise convergence adjustment The noise convergence can be adjusted when there is no input signal by inserting a resistor between pin 33 and ground. •Muting off function Ground pin 33 through a 4kΩ resistor. SOFT MUTE HOLE DET Band muting 50kΩ SD circuit SEEK OFF 10kΩ 33 VCC 50kΩ MUTE AMP. + Equivalent circuit C1 0.1μF 34 35 36 37 AGC QD output QD input VREF •The resistor R1 determines the width of the band muting function. Increasing the value of R1 narrows the band. Reducing the value of R1 widens the band. VCC 0.1μF VREF R1 C 37 R2 36 35 34 •Null voltage When tuned, the voltage between pins 34 and 37, V34 - 37, will be 0V. The band muting function turns on when |V34 - 37| ≥ 0.7V. V37 = 4.9V VCC Quadrature detector HOLE DET 3pF 390Ω 1kΩ IF limiter amplifier Band muting 38 FM SD ADJ A 130μA current flows from pin 38 and, in conjunction with the external resistance R, determines the comparison voltage. 38 R SD ADJ 130μA + -- SD Comparator 24 S-meter Continued on next page. No.6038-12/48 LA1781M Continued from preceding page. Pin No. 39 Pin function Keyed AGC AM stereo buffer Pin description The keyed AGC operates when the voltage created by dividing the pin 24 S-meter output voltage by the 6.4 and 3.6kΩ resistors becomes lower than the voltage determined by the resistor between pin 39 and ground. Comparator 3.6kΩ S-meter 6.4kΩ 24 Equivalent circuit This pin also is used as the AM stereo IF buffer pin. KEYED AGC + -- 1.3V VCC 90μA 39 AM IF out 50pF 150Ω 41 HCC capacitor The HCC frequency characteristics are determined by the external capacitor connected at this pin. + VCC 20kΩ 20kΩ 41 2200pF 42 AM L.C. pin This pin is used to change the frequency characteristics of the unneeded audio band under 100Hz in AM mode to produce a clear audio signal. Note : The LC capacitor must be connected between this pin and VCC (pin 40). This is because the detector circuit operates referenced to VCC. The cutoff frequency fC is determined by the following formula. fC = 1/2π × 50kΩ × C Inserting a 1MΩ resistor between pin 43 and VCC will force the IC to mono mode. 19kHz∠0° BIAS VCC C 42 VCC DET 50kΩ 1kΩ + -- 50kΩ 1kΩ 43 Pilot detector VCC 30kΩ 30kΩ + 30kΩ 43 1μF + Continued on next page. No.6038-13/48 LA1781M Continued from preceding page. Pin No. 44 IF AGC Pin function Pin description G1 ; Used for time constant switching during seeks. • Reception τ = 2.2μF × 300kΩ • Seek τ = 2.2μF × 10Ω The external capacitors are connected to VCC. This is because the IF amplifier operates referenced to VCC. 50kΩ IF AGC DET 50kΩ 42 0.022μF + Equivalent circuit VCC C 2.2μF 240kΩ 44 VCC G1 SEEK ON 10Ω 45 IF output The IF amplifier load Pin 40 VCC 45 Pin 40 VCC DET 46 AM antenna damping drive output Wide band AGC input I46 = 6mA (maximum) This is the antenna damping current. 50pF 46 100Ω VCC 20kΩ VCC W.AGC AMP. ANT DAMPING DRIVER 47 FM muting on level adjustment Modify the value of the external resistor to adjust the muting on level. 30kΩ R 47 VCC 140μA Pin 24 + -- Inverter MUTE Continued on next page. No.6038-14/48 LA1781M Continued from preceding page. Pin No. 48 57 RF AGC Pin function RF AGC bypass Pin description RF AGC rectification capacitor The low frequency distortion is determined as follows : Increasing C48 and C57 improves the distortion but makes the response slower. Reducing C48 and C57 aggravates the distortion but makes the response faster. + Equivalent circuit VCC 5.6V 10kΩ 48 3.3μF + -- Antenna damping For AGC use 57 + 47μF 50 51 IF bypass FM IF input Due to the high gain of the limiter amplifer, care must be taken when choosing the grounding point for the limiter amplifer input capacitor to prevent oscillation. 50 0.022μF 330Ω 51 2.6V 10kΩ 10kΩ IF in 52 IF input The input impedance is 2kΩ. 2kΩ 100Ω 52 53 56 IF amplifier output IF amplifier input • Input and output pin or the first IF amplifier • Inverting amplifier V56 = 2V Input impedance : RIN = 330Ω V53 = 5.3V Output impedance ROUT = 330Ω 2.75V 300Ω IF OUT 53 VCC 300Ω IF IN 56 Continued on next page. No.6038-15/48 LA1781M Continued from preceding page. Pin No. 54 49 Pin function Mixer output : 130μA Mixer input Pin description The mixer coil connected to the pin 54 mixer output must be wired to VCC (pin 40). The pin 49 mixer input Impedance is 330Ω 54 Pin 40 VCC Pin 40 VCC Equivalent circuit OSC 49 330Ω 55 W-AGC IN AM SD ADJ Pins 55 and 58 include built-in DC cut capacitors. The AGC on level is determined by the values of the capacitors C1 and C2. Pin 55 functions as the SD sensitivity adjustment pin in AM mode. The output current I55 is 50μA, and V55 varies depending on the value of the external resistor. The SD function operates by comparing V55 with the S-meter voltage. MIX IN 58 C2 C1 55 30pF Pin 62 VCC W-AGC N-AGC 58 N-AGC IN Muting attenuation adjustment pin 50pF 50μA MIX OUT + -- AM SD Signal meter 59, 60 63, 64 Mixer output Mixer input Double balanced mixer. Pins 59 and 60 are the mixer 10.7MHz output 59 1ST.IF OSC Pins 63 and 64 are the mixer input. This is an emitter insertion type circuit, and the amount of insertion is determined by the capacitors C1 and C2. Note :The lines for pins 63 and 64 must be kept separated from the lines for pins 59 and 60. RF AMP 5pF C2 64 5pF 620Ω 620Ω 30Ω 60 VCC VCC C1 63 Continued on next page. No.6038-16/48 LA1781M Continued from preceding page. Pin No. 6 switching Pin function Front end VCC AM/FM Pin description Pin 6 functions both as the FM front end VCC and the AM/FM switching circuit. V6 voltage Mode FM.F.E AGC 100kΩ 8V 3 GND 3.3V SD + Equivalent circuit VCC 6 510Ω + -- AM/FM switching circuit When 8V → FM OPEN → AM 62 1st MIX INPUT First mixer input The input impedance is about 10kΩ. to RF Amp. 62 10kΩ AM 1st MIX 2.1V 10 AM 2nd OSC Crystal oscillator circuit The Kinseki, Ltd. HC-49/U-S and a CL of 20pF must be used. 10kΩ 5.6V 20pF to 2nd MIX 33pF 10 X tal No.6038-17/48 LA1781M Block Diagram VCC GND 0.022μF TO AM STEREO (IF OUT) 6.8kΩ KEYED AGC 30kΩ FM SD ADJ. PILOT DET AM LC 0.47μF 10kΩ + 0.022μF 2200pF 100μF 0.22μF VREF IF7 1 μF + + 0.47μF 3.3μF 11kΩ 2.2μF CHCC 0.022μF 30Ω 620Ω 0.022μF 1MH 100μH + RFAGC 48 240kΩ 47 46 ANT D 45 44 43 42 0.1μF 40 39 38 10kΩ QD IN AFC IN + + QD OUT + 41 37 36 35 34 MUTE DRIVE 1μF 33 FM 1kΩ 49 FM IF IN 50 51 52 53 54 AM SD ADJ AM MIX OUT 20kΩ FM WB AGCIN FE IF IN 55 56 MIX OSC OSC BUFF MUTE AMP 32 31 30 HOLE DET MUTE DRIVE DC-C AFC DET CLAMP IF BUFF MRC 27 26 HCC 25 29 28 100kΩ 50kΩ AM LEVEL ADJ METER DET OUT FC18 15pF 15pF 100μH 100kΩ 30MH 0.022μF 47μF + 220Ω 100Ω BUFF DET L.C. IF AGC AMVSM AM SD 1μF 0.022μF IF limiter amplifier Q.DET + 8200pF AM HC 1μF NC-IN HCC SNC 1μF + ANTD 0.022μF FM IF OUT + + RF AGC WB AGC TWEET IF AM/FM REG SW SNC 10kΩ GND 510kΩ AM IF IN FMVSM FM SD 100kΩ 5V + GND AM/FM S-METER 0.47μF + SEEK→AM/FM SD STOP→FM ST IND. AM FM VREF 300Ω 200kΩ 0.022μF 2kΩ VCC 30Ω 60 MUTE ATT 59 330Ω 57 62pF 58 W.B.AGC RF AGC SEEK SW SD/ST IND VCO STOP MAIN HC AMP INPUT FF 19k