Audio ICs Double cassette tape recorder system preamplifier BA3426AS The BA3426AS is a record / playback system preamplifier for radio cassette decks. It also has a CD input. It has three control switches for function and tape mode switching and mic on / off. It requires far fewer external components than its predecessors which means simplified assembly and overall savings. Applications Dual-cassette radio cassette players. Features 1) Built-in switch for recording / playback equalize. 2) Motor control output provided. 3) CD input. Absolute maximum ratings (Ta = 25C) Recommended operating conditions (Ta = 25C) 300 4) Smoothing capacitors to suppress switching noise are not required. 5) Built-in bias oscillator transistor. Audio ICs BA3426AS Block diagram 301 Audio ICs Pin descriptions 302 BA3426AS Audio ICs BA3426AS Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 5.5V, f = 1kHz, Rg = 680Ω, Tape input = 66dBm, Mic. input = 50dBm, and Radio input = 23dBm, and CD input = 12dBm) 303 Audio ICs 304 BA3426AS Audio ICs BA3426AS 305 Audio ICs Measurement circuit 306 BA3426AS Audio ICs BA3426AS Circuit operation (1) Control pins The control pin inputs and the corresponding states of the various inputs and outputs are summarized in the input/output pin status table that follows. Control pin inputs and corresponding input / output pin states 307 Audio ICs Application example 1 308 BA3426AS Audio ICs BA3426AS Application example 2 309 Audio ICs Operation notes (1) Amplifier oscillation As the BA3426AS incorporates dual-cassette dubbing functions on a single IC, it has extremely high input / output gain. In particular, in normal-speed mode, the gain at around the recording equalizer peaking characteristic fo frequency is about 70dB. The phases of the input and output are reversed to reduce the chance of oscillation due to influence of the PCB pattern, but due consideration must be given to the PCB pattern design to prevent oscillation. In particular, the PCB tracks to the Tape A pins (pins 1 and 4) and Tape B pins (pins 31 and 32) should be sufficiently far apart that there is no coupling capacitance between them, or they should be shieded by having a GND or bias track between them. Electrical characteristics curves 310 BA3426AS (2) Strong RF signals To prevent signal mixing due to strong electric fields, connect a capacitor (of a few hundred pF) to each input pin. These must be connected close to the pins of the IC to have any effect. Design the PCB track layout so that the capacitors can be connected as close to the base of the pins as possible. Audio ICs BA3426AS External dimensions (Units: mm) 311