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LA1136 AM Tuner System for Car Radios and Home Stereos

LA1137 KIA6037


Overview
 The LA1136N/NM and LA1137N/NM are high-performance AM electronic tuner ICs offering sophisticated functions. They are especially suited for use in car radio and home stereo (antenna: loop) applications.

Functions
 . MIX
. OSC (with ALC)
. IF amplifier
. Detector
. AGC (normal)
. RF wide-band AGC
. Auto search stop signal (Signal meter output)
. Local oscillation buffer output
. IF band switching circuit (for LA1136N only)
. IF count buffer
. Stop detector output (can be set independently)
. Tweet prevention circuit
. AGC (RF, IF) time constant switching circuit
. IF AGC circuit
. Pin-diode driver
. AM stereo decoder IF output (for LA1136N only)
. Circuit preventing incorrect seek operation

Features
 . Excellent cross modulation characteristic: Meets the requirements for preventing not only adjacent-channel interference but also interference caused by all channels within broadcast band.
. Narrow-band signal meter output: Usable as auto search stop signal. Has linearity up to 100 dBµ.
. Local oscillation buffer output: Facilitates designing of electronic tuner system, frequency display, etc.
. OSC (with ALC): Improves tracking error because oscillation output is stabilized at a low level (350 mVrms: LA1137N) for varactor diode.
. MIX: Double-balanced differential MIX meeting the requirements for preventing spurious interference, IF interference.
. Good characteristic at high input: 130 dBµ input fm = 400 Hz 80%mod THD = 0.5% typ.
. High S/N: Good S/N at medium input (55 dB typ).
. Usable sensitivity: (S/N = 20 dB input): 25 dBµ (when using 2SK715 )
. V CC variation compensation: Less variation in gain, distortion: 8 to 12 V
. AM stereo capability (LA1136N only)
. IF band switching circuit on chip; controlled by microcontroller
. Oscillating circuit for AM stereo; SUB S/N improved to 6 dB
. IF output for AM stereo decoder
. Improved tweet characteristics: 10 dB increase, controlled by microcontroller
. Improved cross modulation characteristics, especially sensitivity suppression characteristics: 15 dB improvement, wide-band AGC operation even for SW band interference
. Improved low-frequency modulation distortion
. Improved temperature characteristics: S-meter, SD sensitivity
. Faster RF AGC response: RF: 1/3; IF: 1/8 (compared to predecessors)
. Improved capability for driving external RF AGC transistors: I B max = 200 µA
. Measures to prevent incorrect seek operation
.IF count buffer on chip; controlled by microcontroller
.Time constant switching circuit on chip for RF and IF
AGC
.IF AGC clear circuit on chip
.Measures that prevent stopping one station too soon





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