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| Optical disc ICs 4-channel BTL driver for CD players BA6898S / BA6898FP The BA6898S / BA6898FP ICs contain a 4-channel BTL driver , 5V regulator (which requires an externally connected PNP transistor), multi-purpose operational amplifier, and reset output for use with CD players. Also equipped with an input pin for gain adjustment for all channels of the driver block so that the gain can be adjusted to the desired value for your application. Furthermore, a built-in level shift circuit exists to further reduce the amount of external components required. FApplications CD players, CD-ROM, and other optical disc equipment FFeatures 1) 4-channel BTL driver. 2) Gain is adjustable with externally connected resistor. 3) Internal thermal shutdown circuit. 4) Internal 5V regulator (requires external PNP transistor). 5) Internal multi-purpose operational amplifier. 6) Equipped with reset output pin. FAbsolute maximum ratings (Ta = 25_C) 671 Optical disc ICs FBlock diagram BA6898S/BA6898FP 672 Optical disc ICs BA6898S/BA6898FP 673 Optical disc ICs FPin descriptions BA6898S BA6898S/BA6898FP BA6898FP 674 Optical disc ICs FInput / output circuits BA6898S/BA6898FP 675 Optical disc ICs BA6898S/BA6898FP FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 8V, f = 1kHz, RL = 8) 676 Optical disc ICs FMeasurement circuit BA6898S/BA6898FP 677 Optical disc ICs FCircuit operation (1) Driver block The input is the focus and tracking error signals from the servo pre-amplifier and the control signals for the motor system. The input signal is normally centered at 2.5V, and at the pre-amplifier, it undergoes V / I conversion to generate the current corresponding to the input voltage. This is then passed through a resistor and sent to the internal reference voltage block. BA6898S/BA6898FP This results in the output from the pre-amplifier being the signal at the center of the internal reference voltage. Furthermore, at the V / I conversion, forward and reverse phases are generated and the BTL output is then gained through the driver buffer. (2) Regulator block The configuration is that of a normal series-type regulator and the reference voltage is provided internally. A PNP low-saturation transistor is connected externally. 678 Optical disc ICs FApplication example BA6898S/BA6898FP 679 Optical disc ICs FOperation notes (pin Nos. are those for the BA6898S) (1) Relationship between mute and reset output BA6898S/BA6898FP Regulator voltage drop . . . . . If the regulator voltage drops to 4.0V (Typ.) or below, the reset output turns low and the mute turns on. If the voltage then rises again to 4.2V (Typ.), the reset output turns high and the mute turns off. Bias voltage drop . . . . . . . . . . If the bias pin (pin 3) voltage lowers to 1.4V (Typ.) or below, the mute turns on and the reset output turns low. For normal operations, have the voltage at 1.6V or greater. Thermal shutdown . . . . . . . . . When the chip temperature reaches 175_C (Typ.), the mute turns on and the reset output turns low. If the chip temperature then drops below 150_C (Typ.), then the mute turns off and the reset output turns high. Mute (pin 15) . . . . . . . . . . . . . If the mute pin (pin 15) voltage is open or lowers to 0.5V or below, the mute turns on but the reset output does not change. (2) If the voltage of the thermal shutdown, mute ON, or bias pin drops, or if the regulator voltage drops, the mute is activated; however, in these situations, only the drivers are muted. Also, the output pin voltage becomes the internal bias voltage (approx. (VCC*VF) / 2). (3) Connect a bypass capacitor (approx. 0.1F) between the bases of the power supply pins of this IC. (4) Even though pins 16 and 32 are connected to ground within the package, be sure to also connect them to a ground externally as well. FElectrical characteristic curves (5) The capacitor connected between the regulator output pin (pin 14) and GND also serves to prevent oscillation, so be sure to use a capacitor with excellent thermal characteristics. (6) If the regulator is not used, short the regulator output pin (pin 14) to VCC and have the pin for the externally connected transistor base (pin 13) open. (7) Of the ground pins, only pin 18 is not connected to the IC substrate. Therefore, design the PC board pattern so that the potential of GND pin 18 does not go below the substrate GND (including transient conditions). 680 Optical disc ICs BA6898S/BA6898FP FExternal dimensions (Units: mm) 681 |
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