Stereo FM/AM Receiver CXA1538

Description Of Stereo FM/AM Receiver CXA1538

The CXA1538M/N/S is high performance one-chip bipolar ICs designed for FM stereo/AM radios. These include an FM/AM front end, FM/AM IF amplifier, FM/AM detection output and FM stereo demodulator output. Pin 4 is the stereo indicator and VCO check pin. Therefore, in stereo mode (when stereo indicator drive Tr Q2 is switched on), pin 4 voltage lowers down, Q1 is cut off and VCO oscillation waveform can not be seen. In AM mode as well, the oscillation waveform can not be seen as VCO turns off. 


Adjust the free run frequency at 76 kHz ±50 Hz. This IC has a built-in auto blend circuit and a MONO switch is not required as a rule. This circuit controls the separation in proportion to the signal level and reduces noise automatically for stereo reception below the mid electric field when the electric field strength reaches lower than about 40 dBμ. When the electric field strength turns below 10 to 15 dBμ, MONO operation is automatically activated. To switch MONO mode on externally, ground pin 3 with 33 Kohm. This IC has a built-in soft muting circuit. As shown in the following I/O characteristics diagram, 23 dB (Typ.) muting is applied and noise level reduced during weak electric field and out of tune instances.

Features Of Stereo FM/AM Receiver CXA1538

• Low current consumption (In FM mode ID=11.0 mA, in AM mode 8.5 mA, VCC=6.0 V)
• Built-in LED drive circuit for tuning
• Built-in LED drive circuit for stereo indicator
• Built-in muting circuit for the FM band
• Few external parts