BA6398

Optical disc ICs 4-channel BTL driver for CD players BA6398FP The BA6398FP is a 4-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. FApplications CD players and CD-ROM drives FFeatures 1) 28-pin HSOP package allows for miniaturization of applications. 2) Low number of external components. 3) Driver gain is adjustable with a single attached resistor. FAbsolute maximum ratings (Ta = 25_C) 4) Internal 5V regulator. (requires attached PNP transistor) 5) Internal standard operational amplifier. 6) Internal thermal shutdown circuit. FRecommended operating conditions (Ta = 25_C) 340 Optical disc ICs FBlock diagram BA6398FP 341 Optical disc ICs FPin descriptions BA6398FP 342 Optical disc ICs FInput / output circuits BA6398FP 343 Optical disc ICs FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 8V, f = 1kHz, RL = 8Ω) BA6398FP 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 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. 344 Optical disc ICs (2) Regulator This is a typical series regulator that generates a reference voltage internally. A PNP low saturation types transistor must be connected. BA6398FP (3) Operational amplifier A standard 4558 type. FApplication example 345 Optical disc ICs FOperation notes (1) The BA6398FP has an internal thermal shutdown circuit. Output current is muted when the chip temperature exceeds 175_C (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 4.5V (typically), and starts up again when the voltage rises above 4.7V (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. BA6398FP (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. FElectrical characteristic curves 346 Optical disc ICs FElectrical characteristic curves BA6398FP FExternal dimensions (Units: mm) 347