Optical disc ICs 4-channel BTL driver for CD players BA6297AFP The BA6297AFP is a 4-channel BTL driver for CD player actuators and motors. The preamplifier has both positive and negative input pins and output pins, making this IC suited to a broad range of applications. Applications CD players Features 1) 4-channel BTL driver. 2) HSOP 28-pin package allows for miniaturization of applications. 3) Internal thermal shutdown. Absolute maximum ratings (Ta = 25C) Recommended operating conditions (Ta = 25C) 318 4) Driver gain is adjustable with a single attached resistor. 5) Both positive and negative input pins, for adaptability for a wide range of inputs (including negative phase input). Optical disc ICs BA6297AFP Block diagram Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 8V, f = 1kHz, RL = 8Ω) 319 Optical disc ICs Electrical characteristic curves 320 BA6297AFP Optical disc ICs BA6297AFP Measurement circuit 321 Optical disc ICs Circuit operation The BA6297AFP comprises a 4-channel driver, internal bias amplifier, mute pin and thermal shutdown. (1) Driver The driver uses a buffer to output one of the outputs from its preamplifier with no modification, and uses an inversion amplifier to invert the other output before sending it to the driver buffer. The inversion amplifier’s reference is the bias voltage generated internally (pin 7 voltage), and so the preamplifier output must make the zero level equal to the internal bias voltage. See Figs. 7 and 8 for examples. BA6297AFP (2) Internal bias amplifier Configured as shown in Fig. 9. The internal bias voltage (Vref) is calculated thus : Vref= VCCVF 2 (3) Mute pin (pin 15) The output current is muted when this pin receives the low level or a high impedance. Set the pin voltage at high during normal operation. (4) Thermal shutdown The BA6297AFP has an internal thermal shutdown circuit. Output current is muted when the chip temperature exceeds 175C (typically). 322 Optical disc ICs Operation notes (1) The BA6297AFP has an internal thermal shutdown circuit. Output current is muted when the chip temperature exceeds 175C (typically). (2) If the mute pin (pin 15) voltage is opened or lowered below 0.5V, the output current will be muted. Pin 2 should be pulled up above 2.0V during normal use. During muting, the output pins remain at the internal bias voltage, roughly (VCCVF) / 2. BA6297AFP (3) Be sure to connect the IC to a 0.1µF bypass capacitor to the power supply, at the base of the IC. (4) The radiating fin is connected to the packages internal GND, but should also be connected to an external ground. Application example External dimensions (Units: mm) 323