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Ordering number : EN873F
Monolithic Linear IC
LA1235
FM IF System Applications
Overview
The LA1235 is a high integrated IC developed for use in high S/N, low distortion FM IF system applications. This IC features S/N=88dB, distortion factor=0.015% and has almost all functions required for FM tuner IF stage. The IF amplifier and limiter stage consist of 6 stages of double ended differential amplifier having an excellent AMR, and this stage is followd by the signal meter driver which consists of 4 stages of level detector, thereby creating extended linearity up to strong input. The FM detector stage consists of a double balanced quadrature detector to which a low frequency preamplifire and a muting controller are attached. The muting drive stage consists of an OR circuit for weak signal muting drive output which detects signal intensity and detuning muting drive output which detects S curve DC output and enables the prevention of noise at the time of weak signal and detuning. Further, the weak signal muting drive output circuit contains a Schmitt circuit having hysteresis and enables the prevention of muting malfunction due to amplitude component at the time of weak signal. The AFC output and tuning meter drive stage is of current drive type which makes it possible to adjust AFC sensitivity and muting band width by means of an external resistor, and the built-in tuning meter null (short) circuit foreces the tuning meter to be [0] when th IF amplifier stops working. The IF amplifier stop circuit, being a circuit to stop the FM IF amlifier at the time of AM reception, makes it possible to decrease shock noise due to FM-AM receiving mode switchover.
Package Dimensions
unit: mm 3006B-DIP16
[LA1235]
SANYO: DIP16
Functions
* IF amplifier, Limiter. * Quadrature detection. * AF preamplifier. * Signal intesity muting drive output. * Detuning muting drive output. * AF signal muting circuit. * Signal meter drive output. * AFC, tuning meter drive output. * IF amplifier stop circuit. * Tunig meter null circuit.
Features
* High S/N (88dB typ.). * Low distortion (0.015% typ.). * Weak signal muting dirve output having hysteresis. * Tuning mete null (short) circuit. * Signal meter dirve output having wide dynamic range. * High limiting sensitivity. * Built-in constant-voltage regulated circuit (Operating voltage : 10 to 14V).
SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110 JAPAN O2097HA (KT)/63095HA (KOTO) /O076AT/8044KI, TS/4241KI/3091KI No.873-1/12
LA1235 Specifications Maximum Ratings at Ta=25C
Parameter Maximum supply voltage Input voltage Supply current Flow-in current Flow-out current Allowable power dissipation Operating temperature Storage temperature Symbol VCCmax VIN ICC I5 I10 I13 Pd max Topr Tstg Pin 11 Pins 1 to 2 Pin 11 Pin 5 Pin 10 Conditions Ratings 16 1 40 3 2 2 650 -20 to +70 -40 to +125 Unit V Vp-p mA mA mA mA mA C C
Recommended Operating Conditions at Ta=25C
Parameter Recommended supply voltage Symbol VCC Conditions Ratings 10 to 14 Unit V
Operating Characteristics at Ta=25C, VCC=12V, f=10.7MHz
Parameter Quiescent current Current drain Detection output S/N -3dB limiting sensitivity Muting sensitivity Muting attenuation Muting bandwidth Muting driving output Total harmonic distortion AM supperssion ratio Signal meter driving output VIN(lim) VIN(mute) mute(att) Symbol ICCO ICC VO Quiescent VIN=100dB VIN=100dB, 400Hz, 100% mod. VIN=100dB, 400Hz, 100% mod. VO : -3dB, 400Hz, 100% mod. V12=5.6V, R16=56k, R15=50k VIN=100dB, 400Hz, 100% mod. V5=3.5V BW(mute) VIN=100dB, V12=3V Quiescent V12(1) V12(2) THD AMR V13(1) V13(2) V13(3) V13(4) Offset voltage Tuning meter null voltage IF-off voltage V6-10 V7-10 I15(IF off) VIN=100dB VIN=100dB, 400Hz, 100% mod. VIN=80dB, FM =400Hz, 100% mod, AM =1kHz, 30% mod. Quiescent VIN=35dB VIN=70dB VIN=100dB Quiescent, pin 6 to 10 Quiescent, pin 7 to 10 V2-3=1V 1.3 2.2 -0.8 -0.4 -50 5.6 0 0.1 2.0 3.5 0 0 +5 0.1 0.5 2.9 5.0 +0.8 +0.4 +50 7.5 V V V V V V mV V 45 120 5.6 200 6.2 0 0.015 60 330 6.8 0.3 0.05 kHz V V % dB 80 310 82 Conditions Ratings min typ 21 22 430 88 25 40 100 31 50 max 30 31 Unit mA mA dB dB dB dB
590 mVrms
V7-10(null) V5=7.5V, pin 7 to 10
No.873-2/12
LA1235 Reference Pin Voltage
Pin No. V1 V2 V3 V6 V7 V8 V10 V12 V13 V15 V16 Condition Pin voltage (V) 2.6
6.2 Quiescent 5.9 6.2
0
Test Circuit
Unit (resistance : , capacitance : F)
No.873-3/12
LA1235
* Setting of muting sensitivity, hysteresis width (Refer to the equivalent circuit block diagram and application circuit). Muting sensitivity and hysteresis width are set arbitarily by varying resistors R204 and R205 connected to pins 15 and 16, respectively. Muting sensitivity is set by varying R204 ; and if R204 is made larger, muting sensitivity will shift to the weak signal side. Hysteresis width is set by varying R205 ; and if R205 is made larger, hysteresis width will narrow. Next, how to set muting sensitivity is concretely described as follows. In case of using R204=50k (semifixed resistor) and R 205 =56k, the upper limit of current I 16 , 50 A, delivered from the signal meter driver at which muting is turned ON is obtained from the first quadrant of Table for muting adjustable lower limit calculation. Muting is turned ON at I1650A. If I1650A, muting is already turned ON at a point of input being stronger than the setting input and it is impossible to adjust muting at the setting input. Therefore, I16>50A is required at the setting input. The input at which a sample with a small I16 output meets 50A is obtained as VIN=47dB. This input is the maximum value of muting sensitivity, that is to say, the lower limit at with muting can be set. The data for sample with a Small I16 shown in this Table is colose to the minimum value, but since samples with values less than this munimum value may occur, a margin of some dB must be allowed. From the above, the minimum value for muting setting (muting ON input) becomes 50dB for R204 (semifixed resistor)=50k and R205=56k.
No.873-4/12
LA1235
* Setting of muting circuit constnats Drive current to be output at muting drive output pin 12 is 0.75mA typ., but approximately 0.4mA may be caused by variations in characteristic or changes in temperature (smaller at higher temperatures). It is desirable to design the circuit so that the total current to be output from pin 12 at the time of muting ON does not exceed 0.35mA. When driving the muting circuit of the LA1235, the muting drive current (input current at pin 5) must be considered besides this total output current. The muting drive current of the LA1235 is 0.2mA max. Thus, the muting constants are obrained as follows. If the muting drive current is IR2070.2mA, R20714k occurs and the total current It is shown by the following expression. 4.8V It=IR206+IR207= 6.2V + R206 R206+10k
Muting Circuit
(10k : Input resistance at pin 5, Refer to the above figure.)
If R207=10k is taken with the variation s in voltage V12 at pin 12 and input resistance 10k at pin 5 considered, R20656.4k is obtained, and then R206=68k and R207=10k are obtained. * Setting of C112 (Capacitance between pin 12 and ground) C112 influences S/N and muting attenuation. S/N is improved 0.5 to 2.0dB by changing C112 from 1F to 100F. Muting attenuation becomes as shown in Mute (att) - fm (next page) characteristic. This phenomenon occurs because the output at pin 7 appears at pin 6 through pin 10 and capacitance C110 between pin 7 and ground also exerts influence. The relation between muting attenuation andC110 is such that if C110=2.2F and C112=220F, attenuation at modulation frequency 100Hz becomes -80dB.
AF Output Circuit
No.873-5/12
LA1235 Sample Printed Circuit Pattern
(Cu-coated area 70x60mm2)
Equivalent Circuit Block Diagram and Sample Application Circuit
No.873-6/12
LA1235 Description of external parts
Part Function No. R201 Input resistance (Rg) R202 S meter adjust R203 Muting sensitivity adjust R204 R205 R206 Effect If decreased If increased Causes matching wigh circuit of preceding stage. Current drain increases. S meter pointer is off zero point. (Observe max. rating). (In case of voltage drive type).
R207
R208 R209 R210 R211 R212
C101 C102 C103 C104 S meter output bypass C105 Muting drive output C106 bypass Muting drive output C107 smooth C108 C109 C110 C111 C112 C113 L1 AF output LPF AFC output LPF
Muting sensitivity shifts to weak input side. Hysterisis adjunt Large hysteresis. Small hysteresis. Muting drive circuit load Insufficient drive of detuning muting. When driveing muting of LA3390 (MPX), make less than 200k to prevent malfunction. Abnormal detuning muting Muting time constant Muting response delay. attenuation waveform and abnormal sound at the time of low frequency modulation. IF-off voltage applying Large flow-in current at pin 5 IF-off does not occur. resistnace (Observe max. rating). (IF-off voltage7.5V). AFC, detuning muting Large detuning muting bandwidth. Small detuning muting bandwidth. band width, tuning meter deflection adjust Detection coil damping Small detection output. Large detection output. S curve linearity Find such a value as to cause minimum distortion (THD). correction IF amplifier bypass Unstable IF amplifier.
IF system may be unstable. If low frequency AM compoent is generated in IF signal, weak signal muting flutters. Abnormal detuning muting attenuation waveform and abnormal sound at the time of low frequency modulation. Unstable IF system.
Muting response delay.
Muting response delay.
With MPX connected, separation worsens.
Muting attenuation worsens and Detunig muting response delay. detuning muting bandwidth narrows.
Constant voltage circuit S/N, muting attenuation worsen. smooth Power supply bypass Unstable IF system. Power supply choke Unstable IF system.
Proper cares in using IC
* Connect the ground side of bypass capacitors of pins 2, 3 to an area close to pin 4. * Connect the ground side of bypass capacitors of pins 6, 7, 10, 13, 16 to an area close to pin 14. * Use the shortest possible wires for detection coil-to-pins 8, 9, 10 connection. * Pin 13, being used for signal meter drive output, can be also used multipath detection because IF signal envelope detected is output at this pin.
No.873-7/12
LA1235 Coil specifications
Supplier Sumida Damping resistance Remarks R211 R212 235S01 4.7k 3.3k Containing fixed inductance 26F. SNY-074-1919A 7.5k 2.4k Containing fixed inductance 26F. (Improvement in temperature characteristic). Q228CEL-1077B 13k 3.0k Containing fixed inductance Coil name
Toko
V12 - f
V7 to 10 - f
No.873-8/12
LA1235
No.873-9/12
LA1235
No.873-10/12
LA1235
Cain distribution of application circuit
If IC anone is operated without front end, the tuning meter deflects toward plus side at the time of no input. This phenomenon is caused by the fact that the noise component to be applied to the quadrature multiplication circuit is not syummetric with respect to 10.7MHz but is shifted toward lower frequency side because the frequency characteristic of IF amplifier attenuates at high frequencies and the phase shift circuit is of low-pass type. If the formt end is attached and the noise which passes through the narrowband filter of IF stage and spreads symmetrically with respect to 10.7MHz is stronger than the noise generated inside the IC, the tuning meter reads 0.As the gain of the front end is decreased, input limiting sensitivity and usable sensitivity worsen abruptly. This phenomenon is caused by the fact that since the tuning meter is set to 0 at the time of no input the tuning point of the quadrature circuit must be shifted toward lower frequency side than 10.7MHz and the demodulation output waveform is deformed asymmetrically at an input in the vicinity of usable sensitivity. However, if the gain of the front end is too increased, the signal meter poiter does not return to zero point at the time of no signal.
Sample Application Circuit
Unit (resistance : , capacitance : F)
No.873-11/12
LA1235
No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of which may directly or indirectly cause injury, death or property lose. Anyone purchasing any products described or contained herein for an above-mentioned use shall: Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all damages, cost and expenses associated with such use: Not impose any responsibilty for any fault or negligence which may be cited in any such claim or litigation on SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees jointly or severally. Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for volume production. 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 October, 1997. Specifications and information herein are subject to change without notice.
No.873-12/12

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