BA6897

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. FApplications CD players, CD-ROM drives FFeatures 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. FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions (Ta = 25_C) 391 Optical disc ICs FBlock diagram BA6897S/BA6897FP 392 Optical disc ICs FPin descriptions BA6897S BA6897S/BA6897FP 393 Optical disc ICs BA6897FP BA6897S/BA6897FP 394 Optical disc ICs FInput / output circuits BA6897S/BA6897FP 395 Optical disc ICs BA6897S/BA6897FP FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 8V, f = 1kHz, RL = 8Ω) 396 Optical disc ICs FMeasruement circuit (BA6897S) BA6897S/BA6897FP 397 Optical disc ICs FCircuit operation (1) Driver Inputs to the IC are the focus tracking error signal from the servo preamplifier and the control signal from the motor. 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. (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 Optical disc ICs FApplication examples BA6897S/BA6897FP 399 Optical disc ICs BA6897S/BA6897FP 400 Optical disc ICs FOperation notes (1) The BA6897S and BA6897FP have an internal thermal shutdown circuit. Output current is muted when the chip temperature exceeds 175_C (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. FElectrical characteristic curves 401 Optical disc ICs BA6897S/BA6897FP FExternal dimensions (Units: mm) 402