Optical disc ICs 5-channel BTL driver for CD players BA6395AFP The BA6395AFP is a 5-channel BTL driver for CD player motors and actuators. This IC has an internal 5V regulator, and is suited to a wide range of applications. Applications CD players and CD-ROM drives Features 1) Internal drivers for focus coils, tracking coils, spindle motors, feed motors and loading. (The loading and spindle motor output pins are dual-use output pins and are switched between drivers using a control input.) 2) HSOP 28-pin package allows for miniaturization of applications. Absolute maximum ratings (Ta = 25C) Recommended operating conditions (Ta = 25C) 462 3) Low number of external components. 4) Driver gain is adjustable with a single attached resistor. 5) Internal 5V regulator. (requires attached PNP transistor) 6) Internal thermal shutdown circuit. Optical disc ICs BA6395AFP Block diagram 463 Optical disc ICs Pin descriptions 464 BA6395AFP Optical disc ICs BA6395AFP Input / output circuits 465 Optical disc ICs Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 8V, f = 1kHz, RL = 8Ω) 466 BA6395AFP 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. 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 BA6395AFP 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. 467 Optical disc ICs 4. Channel 2 / loading motor driver output mode switching (VCC = 8V) 468 BA6395AFP Optical disc ICs BA6395AFP (5) Loading motor driver voltage setting Example : Forward motor ∗ Loading driver output voltage cannot be set higher than the maximum output voltage for the power supply. The example above applies only age for the power supply can be output by opening the loading pin (pin 19). when setting below the maximum output voltage. Maximum output volt- Application example 469 Optical disc ICs Operation notes (1) The BA6795AFP has an internal thermal shutdown circuit. Output current is muted when the chip temperature exceeds 175C (typically). (2) If the mute pin (pin 7) voltage is opened or lowered below 0.5V, the output current will be muted. Pin 7 should be pulled up above 2.0V during normal use. (3) The bias pin (pin 23) is muted when lowered below 1.4V (typically). make sure it stays above 1.6V during normal use. (4) The driver circuit shuts down when the supply voltage drops below 4.3V (typically), and starts up again when the voltage rises above 4.5V (typically). (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. Thermal derating curves 470 BA6395AFP (6) The internal input resistor has a positive temperature coefficient of roughly 2000ppm / degree, and so when changing the gain using an attached resistor, gain will also change at a rate of roughly 2000ppm / degree. There is virtually no gain variation due to temperature when using the internal input resistor. (7) Be sure to connect the IC to a 0.1µF bypass capacitor to the power supply, at the base of the IC. (8) The radiating fin is connected to the package’s internal GND, but should also be connected to an external ground. (9) The capacitor between regulator output (pin 6) and GND also serves to prevent oscillation of the IC, so select one with good temperature characteristics. Optical disc ICs BA6395AFP External dimensions (Units: mm) 471