Optical disc ICs
4-channel BTL driver for CD players
The BA6798S is a 4-channel H-bridge BTL driver for CD players and actuators. The 5V regulator and internal standard
operational amplifier make this IC suited to a broad range of applications.
CD players and CD-ROM drives
1) 4-channel BTL driver.
2) SDIP M 24-pin package for high package power.
Absolute maximum ratings (Ta = 25C)
3) Internal thermal shutdown circuit.
4) Driver gain is adjustable with a single attached resistor.
5) Internal 5V regulator. (requires attached PNP transistor)
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Block diagram
Pin descriptions
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Pin equivalent circuit diagrams
Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 8V, f = 1kHz, RL = 8Ω)
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Measurement circuit
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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.
(2) Regulator
This is a typical series regulator that generates a reference voltage internally. A PNP low saturation transistor
must be connected.
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. Both positive and negative phases are created during V / I conversion, generating BTL output via the driver buffer.
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Application example
Operation notes
(1) The BA6798S has an internal thermal shutdown circuit. Output current is muted when the chip temperature
exceeds 175C (typically).
(2) If the mute pin (pin 6) voltage is opened or lowered
below 0.5V, the output current will be muted. Pin 6 should
be pulled up above 2.0V during normal use.
(3) The bias pin (pin 17) is muted when lowered below
1.4V (typically). Make sure it stays above 1.6V during
normal use.
(4) 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 (VCCVF / 2).
(5) 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).
(6) Be sure to connect the IC to a 0.1µF bypass capacitor to the power supply, at the base of the IC.
(7) The capacitor between regulator output (pin 7) and
GND also serves to prevent oscillation of the IC, so select
one with good temperature characteristics.
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Electrical characteristic curves
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External dimensions (Units: mm)