Datasheet BA6798S Datasheet (ROHM)

Optical disc ICs

4-channel BTL driver for CD players

BA6798S

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.

Applications
CD players and CD-ROM drives

Features

1) 4-channel BTL driver.

2) SDIP M 24-pin package for high package power.

Absolute maximum ratings (Ta = 25C)

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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Optical disc ICs BA6798S

Block diagram

Pin descriptions

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Optical disc ICs BA6798S

Pin equivalent circuit diagrams

Electrical characteristics (unless otherwise noted, Ta = 25C, V

CC = 8V, f = 1kHz, RL = 8Ω)

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Optical disc ICs BA6798S

Measurement circuit

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Optical disc ICs BA6798S

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
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.

(2) Regulator
This is a typical series regulator that generates a refer­ence voltage internally. A PNP low saturation transistor
must be connected.

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Optical disc ICs BA6798S

Application example

Operation notes

(1) The BA6798S has an internal thermal shutdown cir­cuit. Output current is muted when the chip temperature
exceeds 175C (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 (V
(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.

CCVF / 2).

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Optical disc ICs BA6798S

Electrical characteristic curves

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Optical disc ICs BA6798S

External dimensions (Units: mm)

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