LA1787M Sanyo Semiconductor Corporation, LA1787M Datasheet
LA1787M
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LA1787M Summary of contents
Page 1
... Ordering number : ENN6655 Overview The LA1787M integrates all six blocks required in a car radio tuner on a single chip. Functions • FM front end • • Noise canceller • Multiplex • AM up-conversion • FM/AM switch • MRC Features • Improved noise reduction methods — ...
Page 2
... V FM FM-2 SM Signal meter output V FM FM-4 SM Muting bandwidth BW-mute Mute drive output V MUTE-100 LA1787M Symbol Conditions V 1 max Pins 6, 40, and max Pins 7, 45, 54, 59, and ≤ 55°C Pd max Topr Tstg Symbol Conditions V Pins 6, 7, 40, 45, 54, 59, 60, and 61 ...
Page 3
... Note: These measurements must be made using the either the IC-51-0644-824 or KS8277 IC socket (manufactured by Yamaichi Electronics When the resistor between pin 58 and ground is 200 kΩ When the resistor between pin 58 and ground is 30 kΩ. LA1787M Conditions 83 MHz, unmodulated. The input such that the pin 2 voltage is 2 below 83 MHz, unmodulated ...
Page 4
... Noise AGC • Pilot signal compensation circuit • Noise sensitivity setting pin • Function for disabling the noise canceller in AM mode LA1787M Multiplex Functions • Adjustment-free VCO circuit • Level follower type pilot canceller circuit • HCC (high cut control) • ...
Page 5
... Pin 53 VA3 IF counter buffer Pin 23 (10.7 MHz/450 kHz) VA4 MPX OUT Left ch Pin 15 (AF) VA5 MPX OUT Right ch Pin 16 (AF) LA1787M SD, stereo, seek/stop Keyed AGC, Mute ATT HCC, SNC, SASC (MRC) Conversion gain measurement (A) When pilot cancellation is used Pin 2 Pin 26 Pin 24 Pin 27 ...
Page 6
... V Used to control the FET 2 RF AGC second gate. 3 F.E.GND 4 OSC Oscillator connection AM first oscillator This circuit can oscillator up to the 7 AM OSC SW band. An ALC circuit is included. LA1787M Description ANT 1000pF – FET 2nd GATE Equivalent circuit pin ...
Page 7
... Recording circuit used during Memory circuit connection 12 noise canceller operation. 13 Pilot input Pin 13 is the PLL circuit input pin. Ground for the N.C., MPX, and 14 N.C, MPX, MRC, GND MRC circuits. LA1787M Description 0. LPF N.C 12 Equivalent circuit 15k ...
Page 8
... Pilot canceller signal output sample-to-sample variations in the IF output level and other parameters. Pin 18 is the output pin for the 18 Pilot canceller signal output pilot canceller signal. LA1787M Description 15 Equivalent circuit V CC 3.3k 3.3k 16 0.015 F 0.015 F A13562 ...
Page 9
... VCO The oscillator frequency is 912 Hz. KBR-912F108 (Kyocera Corporation) CSB-912JF108 (Murata Mfg. Co., Ltd.) 21 PHASE COMP. 22 PHASE COMP. LA1787M Description Composite signal 4k V REF 15k + 15k 19k Equivalent circuit DECODER 5k 19 30k ...
Page 10
... The voltage V23 switches between three modes as follows. FM reception 2.5 V: Forced SD mode: operates 26 Stereo indicator for the SD pin 0.7 V: Reception mode: stereo AM reception: (two modes: 0 and LA1787M Description 4.9V SW Seek mode SD Reception mode AM reception (two modes: 0 and 5 V) Seek mode Reception mode ...
Page 11
... The high band frequency output is controlled 1-V input. It can also be controlled by the 29 HCC control input MRC output. Use a resistor of at least 100 kΩ when controlling with the pin 32 FM S-meter signal. LA1787M Description 100 28 32 Equivalent circuit V CC ...
Page 12
... Adjust the external 1-kΩ resistor DC input to attenuate the MRC AC input and control the circuit. •The muting time constant is •Noise convergence adjustment 33 Mute drive output •Muting off function LA1787M Description determined by an external RC circuit as described below. Attack time kΩ Release time kΩ ...
Page 13
... Keyed AGC becomes lower than the voltage AM stereo buffer determined by the resistor between pin 39 and ground. This pin also is used as the AM stereo IF buffer pin. LA1787M Description V CC determines the 1 width of the band muting function. Increasing the value narrows the band. ...
Page 14
... Note: The LC capacitor must L.C. pin The cutoff frequency f determined by the following formula. f Inserting a 1-MΩ resistor between 43 Pilot detector pin 43 and V to mono mode. LA1787M Description connected between this pin and V (pin 40). CC This is because the detector DET circuit operates referenced ...
Page 15
... V This is because the IF amplifier operates referenced output The IF amplifier load AM antenna damping I46 = 6 mA (maximum) 46 drive output This is the antenna damping Wide band AGC input current. LA1787M Description DET = 2.2 µF 300 kΩ 10 Ω = 2.2 µ Equivalent circuit V CC ...
Page 16
... Due to the high gain of the limiter amplifer, care must be taken when 50 IF bypass choosing the grounding point for input the limiter amplifer input capacitor to prevent oscillation input The input impedance is 2 kΩ. LA1787M Description V CC Pin 3.3 F For AGC use 330 0 ...
Page 17
... N-AGC IN Muting attenuation The output current I55 is 50 µA, adjustment pin and V55 varies depending on the value of the external resistor. The SD function operates by comparing V55 with the S-meter voltage. LA1787M Description IF OUT IF amplifier = 330 Ω 330 Ω OUT IF IN Pin (pin 40) ...
Page 18
... First mixer input 1st MIX 62 The input impedance is about INPUT 10 kΩ. Crystal oscillator circuit 10 AM 2nd OSC The Kinseki, Ltd. HC-49/U-S and a C LA1787M Description 1ST. AMP must be kept separated from the lines for pins 59 and 60. SD and the AM/ voltage ...
Page 19
... F 1 SNC DRIVE HCC MUTE F 1 NC-IN 8200pF ADJ OUT DET LEVEL AM 50k METER FM 100k 0.022 LA1787M F 0. 0.22 30k 5pF 10pF F 0.01 6800pF + OSC COUNTER 1ST AM FF GATE TRIG AGC BUFF BUFF INPUT 38k<0 PICAN AMP FF AMP NOISE ...
Page 20
... FM 22k 6.8k AGC KEYED F 0.22 F 100 CHCC 2200pF 0.022 DET PILOT 2.2 IF7 180k ADJ OR MUTE 15k F 3.3 330 200 50 + LA1787M 100k 100k 100k + + 330 30 20k F 0.022 F 47 100k 200k F 0.022 30k 6.8mH + 10k 1M F 0.015 CH. RIGHT F 0.015 CH. LEFT GND N.C.MPX + 10k ...
Page 21
... S/N-AM Total harmonic distortion (AM) THD- Signal meter output (AM Oscillator buffer output V OSCBUFF AM-1 W-AGCsen 1 Wide band AGC sensitivity W-AGCsen 2 SD-sen1 AM SD sensitivity SD-sen2 AM IF buffer output V IFBUFF-AM LA1787M SW1 SW2 SW3 - OFF - OFF ON b OFF ON b OFF ON b OFF ...
Page 22
... Notes on the LA1781M, LA1784M, and LA1787M The LA1784M is a version of the LA1781M that uses an external oscillator circuit, and has the same characteristics as the LA1781M. The LA1787M is a version of the LA1784M that features improved characteristics. LA1781M This product is a version of the LA1781M with the oscillator circuit removed ...
Page 23
... This makes it easier to adjust the separation. Change in Separation (LA1781M): First IF Input Time after power on — minutes LA1787M 80 100 120 140 Change in Separation (LA1787M): First IF Input Time after power on — minutes No. 6655-23/54 ...
Page 24
... However, this requires 4 more external parts than the LA1781M: 1 transistor and 3 resistors/capacitors LA1787M/1784M FM OSC 3. Gain distribution The table below shows the gain distribution of the LA1780M, LA1784M, and LA1787M. (These are measured values.) Compared to the LA1784M, the total gain is lower. 1st MIX (10.7) LA1780M 10 dB LA1784M 7 ...
Page 25
... Notes on interference rejection characteristics • Intermodulation characteristics The LA1787M applies two high-band AGC functions to prevent IM (the generation of intermodulation). These are the narrow AGC (pin 58: mixer input detection type) and the wide AGC (for the pin 55 input), and this results in the antenna frequency characteristics shown in figure 2. The levels at which the AGC functions turn on are determined by the capacitors attached at pins 55 and 58. f — ...
Page 26
... Frequency, f — MHz LA1787M • Effective in resolving second-channel attenuation problems. ) that is • Allows effective resolution of second-channel attenuation problems without 23 degrading three-signal characteristics. • Seek operations may stop incorrectly due to the occurrence of intermodulation. • possible to prevent the occurrence of intermodulation in the RF tuning circuit and antenna in the presence of strong interfering stations, and blocking oscillation due to AGC operation can be prevented ...
Page 27
... Figure 8 on the next page shows the actual operation of the circuit. f — AGC on Level (ANT input) 110 100 –5 –4 –3 –2 – — MHz LA1787M AGC sensitivity 1 2 Narrow AGC sensitivity (Desired station field strength) Fig when V < 0 98.1 MHz fu = 98.1 MHz + ...
Page 28
... The antenna damping current from the pin due to the pin diode flows when the V2 pin reaches the V level. • The narrow AGC operates as follows. When pin V39 > pin V24: The narrow AGC turns off. When pin V39 < pin V24: The narrow AGC turns on. LA1787M – ...
Page 29
... The LA1787M includes two AGC circuits in its front end block. — Antenna input limiter using a pin diode. — FET second gate control The AGC input pin is pin 59, and the AGC circuit turns on when a signal of about 30 mVrms is input. AGC activation The pin diode drive circuit turns on when V applied to the antenna circuit ...
Page 30
... VT 20pF • Figure 12 shows the type of FM first IF amplifier used in this IC differential single-stage amplifier. 330 TO MIX 56 Specifications Input impedance: 330 Ω Output impedance: 330 Ω Gain LA1787M V CC Fig 330 + 330 – Fig. 12 AM/FM 5 OSC BUFFER OUT ...
Page 31
... Larger V 24 values Smaller values over 0 signal V 23AC IF count OFF buffer V 23DC 5 V New LA1784M functionality: LA1787M R + – – count buffer count output 2.5V 5V Fig. 13 S-meter over 0 ...
Page 32
... Attack Release Fig Sensitivity Adjustment Resistance between the pin and ground — k LA1787M A12080 Mute Muting time constants amp Attack: 10 kΩ 50k Release: 50 kΩ A11766 Fig. C33 C33 No. 6655-32/54 ...
Page 33
... The noise convergence with no input is determined by the pin 58 voltage. 58 100 R 58 A11764 A11765 Fig. 20 LA1787M IF buffer IF amp 5 V Test system capacitance The 10.7 MHz feeds back through ground. Fig. 18 Fig.19 DET out The attenuation can be set by making R33 smaller as listed in the table above ...
Page 34
... Forcing this pin to the ground level turns muting off. Detector 0 output 1 When the pin is at the ground level, the noise convergence will and the –3 dB limiting sensitivity will be about Fig. 24 LA1787M Fig.21 DET out 200 Mute amp. Quadrature detector (VCA) Mute ...
Page 35
... MHz, a search operation will not stop at 98.0 MHz. Since V the situations shown in figure 27 and 28, even though Hall detection would normally not operate and SD would be high, in this IC the Hall detection circuit will operate, V signal will go low, thus preventing incorrect stopping of the search. LA1787M Fig. ...
Page 36
... SA208 + LA1787M IF Input Characteristics Fig.29 –100 –80 –60 –40 –20 –120 With the resistor between pins 36 and 37 open. With resistor between pins 36 and 37. 104 106 Fig. 97.9 MHz 400 Hz, 22.5 kHz dev 98.1 MHz kHz, 22 ...
Page 37
... Resistor R BW between pins 34 and 37 — • AM AGC system The LA1787M RF AGC circuit takes its input from three sources: the WIDE AGC pin (pin 46), the MIDDLE AGC pin (pin 49) and NARROW AGC. There is also an IF AGC circuit 1st MIX 10.7MHz CF ...
Page 38
... FET input when a strong signal is applied to the antenna circuit. The level at which the AGC circuit turns on can be adjusted to an arbitrary level with the wide band AGC adjustment resistor. A delayed AGC on level can be handled by reducing the value of the adjustment resistor. 0.022 100 H LA1787M Fig.33 Wide AGC Operates for wide band interference 1200 Fig ...
Page 39
... SD and the IF buffer are operated by comparing the S-meter level (V24) and the 5 V reference voltage as shown in figure 36. S-meter 100 k Figure 37 shows the relationship between the AM SD, the IF count buffer, and the S-meter. V 24PIN 23AC V 23DC Pin 55 adjustment pin LA1787M AM IF Comparator + – IF buff amp 0. buffer Seek 5 V Fig ...
Page 40
... Therefore, R31 is used to lower the AM detector output level and C31 determines the AM high band frequency characteristics. FM detector AM detector Noise canceler input • AM stereo system pins 45 IF AMP. LA1787M R31 Fig the AM stereo decoder V CC GND ...
Page 41
... However, note that the FM separation characteristics in the high band and the AM frequency characteristics will change 2.5OU IF audio output kHz,180 kHz dev –2.5OU –19.00 s Fig. 43 LA1787M as the reference, C42 must be connected – –20 To pin 31 A12087 – ...
Page 42
... The pilot canceler signal waveform (pin 19 kHz signal that contains no third harmonic as shown in figure 48. Since this signal has the same phase as the pilot signal, no capacitor is required between pin 18 and ground. Since it has no third harmonic component, excellent pilot cancellation can be acquired in both the left and right channels by adjusting with a variable resistor. LA1787M VO (dB) A12090 Fig ...
Page 43
... MRC Noise amplifier High-pass filter with kHz + amplifier An external transistor equivalent to the 2SC536 is required Reason: A QMRC level shifter is required to allow a simplified MRC circuit to be used in the LA1787M. Fig. 50 Larger A12094 100 QMRC 27 + C27 V CC ...
Page 44
... As a result the noise exclusion efficiency was reduced by this delay in the rise time. In the LA1787M, this rise time was shortened by implementing the circuit that determines the gate time in logic, allowing it to reliably exclude noise. ...
Page 45
... Gain Distribution (FM) This section investigates the gain in each block in the LA1787M when the Sanyo recommended circuits are used. (Test conditions) Ambient temperature: 26°C Antenna and mixer input frequency: 98.1 MHz First and second IF input frequency: 10.7 MHz The input levels when will be as follows. ...
Page 46
... This section investigates the gain in each block in the LA1787M when the Sanyo recommended circuits are used. (Test conditions) Ambient temperature: 26°C Antenna and mixer input frequency: 1 MHz First and second mixer input frequency: 10.7 MHz Second IF input frequency: 450 kHz The gains at each stage will be as follows. ...
Page 47
... IF input 75 300 10.7 MHz [AM] • First mixer input 0.022 • IF input 0.022 450 kHz LA1787M • First IF input 10.7 MHz Actual measurement A11775 0.022 F 51 330 50 0.022 F A11777 • Second mixer input 62 A11778 • Del input ...
Page 48
... OSC 2 f OSC 1st MIX 10.71 MHz 1st OSC 10.7 MHz LA1787M 2nd MIX CF CF 450K 300 XBUFF LC72144 AM 1st IF Step 10.25 MHz 10.7 MHz 10 kHz, 11 kHz 10.35 MHz 10.8 MHz 9 kHz, 10 kHz 2nd OSC 10.26 MHz ...
Page 49
... amplifier (RC875-222J) 0.1ø2UEW [FM Block (SA-1060 OSC (SA-1052 DET (SA-208 LA1787M AM OSC (SA-359 IF2 (SA-1063 ANT IN (SA-1048 ANT (SA-1061 ...
Page 50
... Block (V666SNS-208AQ ø0.1–2UEW OSC (V666SNS-205APZ ø0.12–2UEW DET (DM600DEAS-8407GLF 0.07ø2MUEW LA1787M AM OSC (V666SNS-214BY 0.1ø2UEW IF2 (7PSGTC-5002Y 0.05ø3UEW ANT IN (385BNS-027Z ANT (V666SNS-209BS) 3 ...
Page 51
... FM RF (000021064 OSC (000021066 62.7nH DET (010021075 1 3-4 : 120pF 1 6 LA1787M AM OSC (000021056 5 IF2 (000021059 180pF ANT IN (000021062 100 ANT (000021065) ...
Page 52
... LA1787M Antenna input — dBµ Antenna input — dBµ Input — dBµ Mixer input — dBµ Antenna input — dBµ Antenna input — dBµ Input — dBµ First IF input — dBµ No. 6655-52/54 ...
Page 53
... AM DC Characteristics 7 8 AGC MHz 6.0 5.0 4.0 3.0 2.0 1.0 0 – 100 ANT input, IN — dB LA1787M Frequency, — MHz Ambient temperature, Ta — °C AM I/O Characteristics 8 MHz mod = 1 k 30% 0 –20 –40 –60 –80 –100 – ANT input, IN — Distortion 7 ...
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... SANYO believes information herein is accurate and reliable, but no guarantees are made or implied regarding its use or any infringements of intellectual property rights or other rights of third parties. This catalog provides information as of July, 2002. Specifications and information herein are subject to change without notice. LA1787M AM Second-Channel Interference 20 40 kHz desire mod ON ...