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Ordering number : EN737F
Monolithic Linear IC
LA1245
AM Electronic Tuner
Overview
Package Dimensions
LA1245 is a high performance IC to be used as an AM unit : mm electronic tuner. It provides an automatic search-stop 3021B-DIP20S signal, local oscillator buffer-output, and the low level local oscillation, as well as providing all other functions required of an AM tuner. Moreover, the stable local oscillation from LW to SW facilitates the use of many band.
[LA1245]
Functions
· RF amplifier · MIX · OSC (with ALC) · Detection · IF amplifier · AGC · Local oscillation buffer-output · Signal meter driving output (also used as an automatic search stop-signal) · etc.
SANYO: DIP20S
Features
· Narrow-band signal meter · Local oscillation buffer-output · OSC (with ALC) · RF amplifier · MIX · Low noise · Compensation for VCC fluctuation · Low shock noise : Available as an automatic search-stop signal (also available as a wide-band signal meter). Signal meter output=1/2 frequency ±1.5kHz typ. : Facilitates the design of electronic tuning systems and frequency representation. : The oscillation output is stabilized at a low level (350 mVrms) for a varactor diode, and tracking error is minimized. : Excellent in usable sensitivity by incorporating low-noise transistors in cascode circuit (45dB/m typ). : Double balanced differential MIX prevents the influence of spurious radiation and IF interferences (IF interference = 85dB typ). : Excellent in S/N for intermediate input (57dB typ). : Allows little gain fluctuation and little distoriton fluctuation (8 to 16 V). : Able to decrease the shock noise by selecting AGC time constant when changing VCC-on and/or switching the mode.
SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110 JAPAN 63097HA (KOTO)/33194HO/N050JK/8044KI,TS3173KI/O020KI No.737-1/11
LA1245 Specifications Maximum Ratings at Ta=25°C
Parameter Supply voltage Output voltage Input voltage Supply current Output high drive current Allowable power dissipation Operating temperature Storage temperature Parameter Recommended supply voltage Symbol VCCmax Vo VI ICCmax I18 I20 Pd max Topr Tstg Symbol VCC Conditions Pin 8, 14 Pin 5, 7 Pin 3 Pin 5+7+8+14 Pin 18 Pin 20 See Figure 2 Conditions Ratings 16 24 5.6 32 5 2 700 20 to +70 40 to +125 Ratings 12 Unit V V V mA mA mA mA °C °C Unit V
Recommended Operating Conditions at Ta=25°C
Operating Characteristics at Ta=25°C, VCC=12V, fr=1MHz, fm=400Hz, at specified test circuit
(based on application circuit).
Parameter Current drain Detection output Signal to noise ratio Total harmonic distortion Signal meter output Input at signal meter output=1V Local oscillation-buffer output Symbol ICC1 ICC2 Vo1 Vo 2 S/N1 S/N2 THD1 THD2 VSM1 VSM3 VIN1 Vosc quiescent 107 dBµ input 23 dBµ input, mod. 30% 80 dBµ input, mod. 30% 23 dBµ input, mod. 30% 80 dBµ input, mod. 30% 80 dBµ input, mod. 30% 107 dBµ input, mod. 30% quiescent 107 dBµ input VSM output=1V 3.0 19.0 250 Conditions Ratings min 16.0 19.0 27.5 15.5 16 52 typ 25.0 29.0 23.0 12.5 20 57 0.4 0.3 0 4.5 25.0 350 Ratings min typ 2.5 2 10 ±1.5 4.5/+7 45 85 40 max 1.0 1.0 0.5 7.0 31.0 max 35.0 40.0 18.5 9.5 Unit mA mA dBm dBm dB dB % % V V dBµ mVrms
Reference Characteristics
Parameter Signal meter output Total harmonic distortion Local oscillation fluctuation within a band Signal meter band width* Selectivity IF interference Image frequency interference ratio VSM-BW1 VSM-BW2 Symbol VSM2 THD3 Vosc Conditions 40 dBµ input 112 dBµ input, mod.30% VoscL (522kHz) to VoscH (1647kHz) 80 dBµ input, 1/2 output frequency 80 dBµ input, 1/10 output frequency ±10kHz at 30% mod. fr=600kHz fr=1400kHz kHz kHz dB dB dB Unit V % mVrms
* BFB450C4 N (Murata, Co.,) was used as a narrow band filter. (Note) 0 dBm=775mV, 0 dBu=1µV.
No.737-2/11
LA1245 Using the automatic search-stop signal
Signal Meter-driving output circuit is equivalent to Figure. 1, signal meter driving output (abbreviated as VSM) is narrowed in band width and can be used as an automatic search-stop signal when a narrow band series resonator is connected to pin 15. VSM can be adjusted with R208 and R211 both in wide band and narrow band since R208 is inversely proportional to VSM, while R211 is proportional to VSM. R208 is related to the Q of narrow band signal meter. When the resistance of R208 is increased, the Q will be damped and the band width increased. On the other hand, R211 used as the output impeadance of VSM and affects the cut-off frequency and time constant of low pass filter for VSM and the meter drive impedance. The time constant and the cut-off frequency fc can be expressed as follows : = (C114+C115+CS) (R211//Rin) 1 fc = 2 A semi-fixed resistor is recommended to be used as R211 to cope with the fluctuation of VSM. Refer to Figure. 3 for the value of the semi-fixed resistor since this depends upon VSM and R208. Figure. 3 shows the lowest limit of the semi-fixed resistor in relation to R208 with the parameter of VSM set point, and the value of the semi-fixed resistor will be equal to or greater than that shown in Figure. 3. For example, when VSM=5V and R208=240, R211 becomes 28k. Thus, the value of the semi-fixed resistor is determined to be about 30k. When the value of VSM is too large, it is limited and saturated to the source voltage so it is recommended to follow the condition of VSMVCC2(V). When a narrow band serial resonator is used, include the resonant impedance to determine the value of R208.
No.737-3/11
LA1245
Notes on LA1245 usage
1. When suddenly tuned to a broadcasting station of intermediate or high field strength, a large current of high frequency flows into the signal meter circuit, causing the local oscillator malfunctions and abnormal noises. To eliminate this : · Use R208240 for manual tuning type. · Use R20882, and use the local oscillation coil at the 1/3 tap (except SW) for electronic tuning type (which uses a narrow band filter). 2. Use the bias on the condition RF VCCIF VCC, since abnormal noise levels might be caused when detuning a strong input on the codition RF VCC>IF VCC. 3. Use the signal meter driving output (VSM) at VSMVCC2 (V) to avoid saturation caused by VCC. 4. Use 1/2 or more tap of LW and MW oscillation coil to improve S/N and the detuning characteristics of the distortion ratio. 5. Use the full-tap of SW oscillation coil, to allow the sag in oscillation power by the decreasing of Q. 6. Avoid the coupling of the antenna tuning circuit and the local oscillating circuit so as not to leak the local oscillation into the antenna tuning circuit. 7. Connect the detection capacitor C113 between pin 13 (output) and pin 14 (VCC) to avoid the leakage of the IF signal into the GND line. Connection between pin 13 and pin 12 (GND) increases the tweet interference and deteriorates the usable sensitivity. Moreover, depending on the positions of C113 and the bar antenna, higher harmonics having twice or three times the frequency of the IF signal may pass into the antenna and cause tweet interference, and in extreme cases oscillation might be cause. To prevent this : · Shorter lead wires and connect them near 13 and 14 pins. · Place C113 far from the antenna.
No.737-4/11
LA1245
8. When a cable or something similar is connected to a local oscillation buffer (pin 20), which is equivalent to connecting a capacitor of about 20pF, the output from the buffer will be of sawtooth waves, causing the level low at the short wave band. To prevent this, connect a resistor between pin 20 and GND, which will increase the operating current of the buffer amplifier. Since the maximum current obtained from pin 20 is 2mA, the suitable resistance between pin 20 and GND is 1.5k. 9. Use a semi-fixed resistor for R211 to allow the fluctuation of VSM. 10. When changing an IFT or using an RF tuner, select a filter and related circuits according to the following conditions. The input levels of each terminal where 30% modulated detection output of 25dBm is obtained are as follows : Pin 11 input when Rg=520 (470 + 50) 75dBµ Pin 9 input when Rg=50 53dBµ Pin 6 input when Rg=50 48dBµ Pin 3 input when Rg=50 22dBµ Slight change in IFT, however, will be covered by changing the constant of resistors R202 and R204. 11. When the coupling coefficient of the local oscillation coil is small and an anti-resonance point of about 100MHz is present or the stray capacitance between pin 19 and pin 20 is large, the buffer output (pin 20) may be subject to parasitic oscillation of about 100MHz. In this case, connect a capacitor of about 30pF between pin 20 and GND. To observe parasitic oscillation, connect a capacitor of 5pF in series with the probe. If the probe is connected direct to pin 20, the input capacitance of the probe causes parasitic oscillation to stop, which makes it impossible to observe.
Sample Application Circuit 1
Unit (resistance : , capacitance : F) No.737-5/11
LA1245
No.737-6/11
LA1245
No.737-7/11
LA1245
Sample Application Circuit 2 : Using variable capacitance diodes
No.737-8/11
LA1245
Sample Application Circuit 3 : Rejecting IFT (II)
Following 2 changes are recommended as C-conpling without IFT (II)
Comparison of characteristics varying parts.
No.737-9/11
LA1245
Peripheral Parts
(1) Bar Antenna (34H-052-869 Sumida Co.,)
(2) Bar Antenna (C-4698 Coil Snake Co.,)
(3) Osc coil
No.737-10/11
LA1245
(4) Variable Capacitor (C123A Alps Co.,)
c max c min 326.8 pF 6.7 pF
(5) Variable Capacitor Diode (SVC332 Sanyo) (6) IFT (I) (CMFQ-021A Toko Co.,)
(7) IFT (II)
(8) Narrow Band Resonator (BFB450C4 N Murata Co.,)
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 June, 1997. Specifications and information herein are subject to change without notice.
No.737-11/11