Optical disc ICs 4-channel BTL driver for CD players BA5931FP The BA5931FP is a 4-channel BTL driver designed for CD player motors and actuators. The 28-pin HSOP package allows for application miniaturization. FApplications CD players, CD-ROM drives FFeatures 1) Internal drivers for focus coils, tracking coils, spindle motors, feed motors and loading. 2) HSOP 28-pin package allows for miniaturization of applications. FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions (Ta = 25_C) 278 3) Low number of external components. 4) Driver gain is adjustable with a single attached resistor. 5) Internal thermal shutdown circuit. Optical disc ICs BA5931FP Block diagram Pin descriptions 279 Optical disc ICs Input / output circuits 280 BA5931FP Optical disc ICs BA5931FP FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 8V, RL = 8Ω, Vb = 2.5V) 281 Optical disc ICs Measurement circuit 282 BA5931FP 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 BA5931FP 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. 283 Optical disc ICs (2) BA5931FP Switching the loading motor driver output mode (VCC = 8V) Note: Loading driver gain = 0dB (3) Setting the loading driver voltage (forward mode) Note: The loading output voltage will not exceed the power supply’s maximum output voltage, even if set above this maximum voltage. The example above applies only when setting below the maximum output voltage. Maximum output voltage for the power supply can be output by opening the loading input pin (19 pin). 284 Optical disc ICs BA5931FP Application example 285 Optical disc ICs FOperation notes (1) The BA5931FP has a thermal shutdown circuit. The output current is muted when the chip temperature rises above 175_C (typically). (2) The IC is muted when the bias pin (pin 23) is lowered below 1.4V (typically). Make sure it stays between 1.6V and 6.5V during normal use. (3) Muting occurs during thermal shutdown or a drop in the bias pin voltage. In each case, only the drivers are FElectrical characteristic curves 286 BA5931FP muted. During muting, the output pins remain at the internal bias voltage, (approx VCC / 2). (4) Connect the IC to a 0.1µF bypass capacitor between power supplies, at the base of the IC. (5) The radiating fin is connected to the package’s internal GND, but should also be connected to an external ground. Optical disc ICs BA5931FP External dimensions (Units: mm) 287