Optical disc ICs 4-channel BTL driver for CD players BA6392FP The BA6392FP is a 4-channel BTL driver for CD player motors and actuators. It has an internal primary filter, and can be directly connected (without attached components) to the servo PWM output of all drivers other than the spindle driver. The BA6392FP is pin compatible with the BA6297AFP. Applications CD players, CD-ROM drives Features 1) HSOP 28-pin package allows for miniaturization of applications. 2) PWM input is filtered by the internal primary filter, eliminating the need for attached resistors and capacitors, thereby helping reduce the number of components. Resistor and capacitor time constants can also be changed with attached components. Absolute maximum ratings (Ta = 25C) Recommended operating conditions (Ta = 25C) 324 3) Internal thermal shutdown circuit. 4) Internal mute circuit. Optical disc ICs BA6392FP Block diagram 325 Optical disc ICs Pin descriptions 326 BA6392FP Optical disc ICs BA6392FP Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 8V, f = 1kHz, RL = 8Ω) 327 Optical disc ICs BA6392FP Input / output circuits Circuit operation (1) Fig. 3 shows the inputs from the digital servo IC for CH1-CH3 drivers (all drivers except the spindle). SW1 is on when the forward input signal (HIGH level, over 2.4V) is present. SW2 is on when the reverse input signal is present (Fig. 2) The constant current (I1) at this time enters the RC and generates an integral waveform based on the duty of the input waveform. The BTL is output from BUF1 and BUF2 (Fig. 4). 328 To maintain the HIGH level with forward (or reverse) input, the DC voltage generated at point A is : I1 R 2.5V (reverse : 2.5V) This is the voltage generated relative VREF. The setting is such that a voltage differential of 5V is generated between output pins. The time constant is : R C = 2.4µsec Optical disc ICs This can be increased by inserting a capacitor between point A (pins 3, 11 and 18) and VREF. The constant current (Iconst) given in the electrical characteristics refers to I1 and I2 in Fig. 2. BA6392FP Operation notes (1) The BA6392FP has an internal thermal shutdown circuit. Output current is muted when the chip temperature exceeds 180C (typically). (2) The output current can also be muted by lowering the mute pin (pin 15) voltage below 0.5V. (3) All four driver output channels are muted during thermal shutdown, muting and a drop in bias pin voltage. No other components are muted. (2) CH4 driver (spindle driver) Pins 23 and 25 are shorted inside the IC. Bias amplitudes are the primary type of inputs assumed. The level shift circuit converts the pre-stage amplifier output (centered on the bias level and impressed on pins 23 and 25) to positive and negative amplitudes centered on VREF. The level shift circuit’s output is BTL-output from the buffer amplifier. Because of the high input impedance, the IC is designed to accommodate a filter comprising attached resistors and capacitors. (Example) For secondary filters 329 Optical disc ICs Electrical characteristics curves 330 BA6392FP Optical disc ICs BA6392FP External dimensions (Units: mm) 331