523
Motor driver ICs
3-phase motor driver
BA6840BFS / BA6840BFP-Y / BA6840BFP /
BA6842BFS
The BA6840BFS, BA6840BFP-Y, BA6840BFP, and BA6842BFS are one-chip ICs designed for driving CD-ROM motors.
They are high performance-ICs with a 3-phase, full-wave, pseudo-linear drive system.
F
Applications
CD-ROM / RW, DVD-ROM / PLAYER
F
Features
1) 3-phase, full-wave, pseudo-linear drive system.
2) Start / stop pin; power saving during stop mode.
3) Internal current limit circuit.
4) Internal thermal shutdown circuit.
5) Internal hall bias circuit.
F
Block diagram
524
Motor driver ICs
BA6840BFS / BA6840BFP-Y / BA6840BFP / BA6842BFS
F
Absolute maximum ratings (Ta = 25
_
C)
F
Recommended operating conditions
525
Motor driver ICs
BA6840BFS / BA6840BFP-Y / BA6840BFP / BA6842BFS
F
Electrical characteristics (unless otherwise noted, Ta = 25
_
C, V
CC
= 5V, V
M
= 12V)
527
Motor driver ICs
BA6840BFS / BA6840BFP-Y / BA6840BFP / BA6842BFS
F
Circuit operation
(1)
Hall input
X
output
The 3-phase Hall signal is amplified in the hall amplifiers
and sent to the matrix section, where the signal is further
amplified and combined. After the signal is converted to
a current in the amplitude control circuit, the current is
supplied to the output driver, which then provides a motor
drive current. The phases of the Hall input signal, output
voltage, and output current are shown in Fig. 5.
(2)
Torque control pin
The R
NF
-pin current depends on the torque control input
voltage (EC) as shown in Fig. 6.
(3)
Start / stop pin
The motor is in the run mode when the pin input voltage
is 3.5V or more, and in the idle mode (all output transis-
tors are off) when the voltage is 1.5V or less.
(4)
Power ground pin (R
NF
pin)
The R
NF
pin is the output stage ground pin. Connect a re-
sistor (0.5
recommended) between this pin and the
ground to monitor the output current.
(5)
Phase compensation pin (C
NF
pin)
Connect and adjust a capacitor between this pin and the
ground if the output tends to oscillate.
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