BA6896FP

Optical disc ICs 4-channel BTL driver for CD players BA6896FP The BA6896FP is a 4-channel BTL driver designed for CD player motor and actuator drives. The internal 5V regulator and standard operational amplifier make this IC suitable for a wide spectrum of applications. FApplications CD players, CD-ROM drives FFeatures 1) HSOP 28-pin package, for application miniaturization. 2) A minimum of attached components. 3) Driver gain is adjustable with a single attached resistor. 4) Internal 5V regulator. (requires attached PNP transistor) FAbsolute maximum ratings (Ta = 25_C) 5) Internal standard operational amplifier. 6) Internal thermal shutdown function. 7) The output current between pins 1 and 2 is mutable with the external mute pin. 382 Optical disc ICs FBlock diagram BA6896FP FPin descriptions 383 Optical disc ICs FPin equivalent circuit diagrams BA6896FP 384 Optical disc ICs FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 8V, f = 1kHz, RL = 8Ω) BA6896FP 385 Optical disc ICs FMeasurement circuit BA6896FP 386 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. 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 BA6896FP 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) Operational amplifier A standard 4558 type. 387 Optical disc ICs FApplication example BA6896FP 388 Optical disc ICs FOperation notes (1) The BA6896FP has an internal thermal shutdown circuit. Output current is muted when the chip temperature exceeds 175_C (typically). (2) The output current can be muted be raising the mute pin (pin 7) voltage above 2.2V. Pin 7 should be open or pulled up above 0.4V during normal operation. (3) Muting also occurs when the bias pin (23 pin) drops below 1.4V (typically). Pin 23 should stay above 1.6V during normal operation. (4) The internal circuits turn off when the supply voltage drops below 4.5V (typically) and start up again when the supply voltage rises above 4.7V (typically). BA6896FP (5) Muting occurs during thermal shutdown, mute-on operations or a drop in the bias pin voltage or supply voltage. In each case, only the drivers are muted. During muting, the output pins remain at the internal bias voltage, roughly (VCC*VF) / 2. (6) Attach a bypass capacitor (roughly 0.1µF) to the power supply, at the base of the IC. (7) The radiating fin is connected to the package’s internal GND, but should also be connected to an external ground. (8) The capacitor between regulator output (pin 6) and GND also serves to prevent oscillation of the IC, so select one with good temperature characteristics. FThermal derating curve FElectrical characteristic curves 389 Optical disc ICs BA6896FP FExternal dimensions (Units: mm) 390