374
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.
F
Applications
CD players and CD-ROM drives
F
Features
1) 4-channel BTL driver.
2) SDIP M 24-pin package for high package power.
3) Internal thermal shutdown circuit.
4) Driver gain is adjustable with a single attached resis-
tor.
5) Internal 5V regulator. (requires attached PNP tran-
sistor)
F
Absolute maximum ratings (Ta = 25
_
C)
376
Optical disc ICs
BA6798S
F
Pin equivalent circuit diagrams
F
Electrical characteristics (unless otherwise noted, Ta = 25
_
C, V
CC
= 8V, f = 1kHz, R
L
= 8
)
378
Optical disc ICs
BA6798S
F
Circuit operation
(1)
Driver
Inputs to the IC are the focus tracking error signal from
the servo preamplifier and the control signal from the mo-
tor.
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 sig-
nal centering on the internal reference voltage. Both pos-
itive and negative phases are created during V / I conver-
sion, generating BTL output via the driver buffer.
(2)
Regulator
This is a typical series regulator that generates a refer-
ence voltage internally. A PNP low saturation transistor
must be connected.
PDF 
ZIP
