Optical disc ICs 4-channel BTL driver for CD players BA6897S / BA6897FP The BA6897S and BA6897FP are a 4-channel BTL driver for CD player motors and actuators. It has an internal 5V regulator and standard operational amplifier, and is suited to a wide range of applications. Applications CD players, CD-ROM drives Features 1) Minimal number of external components. 2) Driver gain is adjustable with just one attached resistor. 3) Internal 5V regulator (attached PNP transistor necessary). 4) Internal standard operational amplifier. 5) Internal thermal shutdown circuit. Absolute maximum ratings (Ta = 25C) Recommended operating conditions (Ta = 25C) 391 Optical disc ICs Block diagram 392 BA6897S/BA6897FP Optical disc ICs BA6897S/BA6897FP Pin descriptions BA6897S 393 Optical disc ICs BA6897FP 394 BA6897S/BA6897FP Optical disc ICs BA6897S/BA6897FP Input / output circuits 395 Optical disc ICs BA6897S/BA6897FP Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 8V, f = 1kHz, RL = 8Ω) 396 Optical disc ICs BA6897S/BA6897FP Measruement circuit (BA6897S) 397 Optical disc ICs Circuit operation (1) Driver Inputs to the IC are the focus tracking error signal from the servo preamplifier and the control signal from the motor. (2) Regulator This is a typical series regulator that generates a reference voltage internally. A PNP low saturation transistor must be connected. (3) Amplifier General 4558 type. 398 BA6897S/BA6897FP The input signals, which normally center on 2.5V, are V / I converted by the preamplifier, generating a current corresponding to the input voltage. This current is passed through a resistor and into the internal reference voltage component, the preamplifier output being a signal centering on the internal reference voltage. Two systems (positive phase and negative phase) are created during V / I conversion, generating BTL output via the driver buffer. Optical disc ICs BA6897S/BA6897FP Application examples 399 Optical disc ICs 400 BA6897S/BA6897FP Optical disc ICs Operation notes (1) The BA6897S and BA6897FP have an internal thermal shutdown circuit. Output current is muted when the chip temperature exceeds 175C (typically). (2) If the mute pin voltage is opened or lowered below 0.5V, the output current will be muted. The mute pin should be pulled up above 2.0V during normal use. (3) The bias pin is muted when lowered below 1.4V (typically). Make sure it stays above 1.6V during normal use. (4) Muting occurs during thermal shutdown, mute-on operations or a drop in the bias pin voltage or supply volt- BA6897S/BA6897FP age. In each case, only the drivers are muted. During muting, the output pins remain at the internal bias voltage, roughly (VCC–VF) / 2. (5) Be sure to connect the IC to a 0.1µF bypass capacitor to the power supply, at the base of the IC. (6) The radiating fin is connected to the packages internal GND, but should also be connected to an external ground. (7) The capacitor between regulator output (pin 6) and GND also serves to prevent oscillation of the IC, so select one with good temperature characteristics. Electrical characteristic curves 401 Optical disc ICs External dimensions (Units: mm) 402 BA6897S/BA6897FP