Motor driver ICs
3-phase motor driver for
CD-ROMs
BA6849FP / BA6849FP-Y / BA6849FM /
BA6849FS
The BA6849 series are ICs developed for CD-ROM spindle motor drives. These ICs possess a short brake and reverserotation brake for two types of brake functions, and also contain FG output and rotation direction detection (FR) circuits,
making them high-functionality and high-performance ICs.
Applications
CD-ROM, CD-R, CD-RW, DVD-ROM, and DVD-RAM
Features
1) Three-phase, full-wave, pseudo-linear drive system.
2) Built-in power save and thermal shutdown functions.
3) Built-in current limiter and Hall bias circuits.
4) Built-in FG output.
5) Built-in rotation direction detector.
6) Built-in reverse rotation prevention circuit.
7) Built-in short brake pin.
Absolute maximum ratings (Ta = 25C)
863
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
Recommended operating conditions (Ta = 25C)
Block diagram
864
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
Pin descriptions
BA6849FP/BA6849FM BA6849FP-Y
865
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
MA6849FS
866
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
Input / output circuits
(1) Power save
(2) Torque command input
(3) Torque output (A
(4) Hall input (H
1
1, A2, and A3)
, H1–, H2, H2–, H3, H3–)
867
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
(5) Hall bias
(6) FG output
(7) FR Output
(8) Short brake
868
Note: Resistance values are typical values.
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 5V, VM1 = 12V, VM2 = 12V)
869
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
Circuit operation
(1) Hall input to coil output
The phase relationship between the Hall input signals and the output current and voltage is shown in Fig.9. The motor
position data input via the Hall pins is amplified by the Hall amplifier, and formed into waveforms by the matrix
block.These signals are input to the output driver that supplies the drive current to the motor coils.
870
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
(2) Torque command
NF pin voltage with respect to the torque command
The R
C) is as follows:
(E
(3) Reverse rotation detection function
The reverse detection circuit construction is shown in
Fig.11.
(1) Forward (E
C < ECR)
The phase relationship between the Hall input signals
H2
and H3 becomes as shown in Fig.9, and the reverse rotation detection circuit does not operate.
(2) Reverse (E
The phase relationship between the signals H
3
is opposite that for forward operation, and the re-
H
C > ECR)
2
and
verse rotation detection circuit operates. The output
goes OFF, and becomes open circuit.
The I / O gain (G
EC) from the EC pin to the RNF pin (output
current) is determined by the R
G
EC = 0.255 / RNF [A / V]
The torque limit current I
TL = 0.35 / RNF [A]
I
TL is given by:
NF detector resistor.
871
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
(4) Short brake
When 3.5V or more is applied to the short brake pin, the
upper-side output transistors of all go off, and the lowerside output transistors go on. Short braking operates regardless of the torque command signal.
Application example
(5) Other circuits
When 3.5V or more is applied to the power save pin, all
circuits are on. When 1.5V or less is applied, the IC enters power save mode. Also, the Hall bias pins turn on
and off with the power save pin.
872
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
Operation notes
(1) Power save
The power save input is an I / O circuit like the own
shown in Fig.1.
The thermal derating characteristics of the power save
pin is –8mV / C, and the resistance will fluctuate between ±30% so be careful of the input voltage range.
(2) Hall input
The input circuit shown in Fig.4 is used for the Hall inputs.
The Hall elements can be connected either in series or
in parallel.
(3) Thermal shutdown (TSD)
When the junction temperature reaches 175C, the A
A
2, and A3 coil outputs go open circuit. The thermal shut-
down has approximately 15C of hysteresis.
1,
Electrical characteristics curves
873
Motor driver ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
External dimensions (Units: mm)
874
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