Rohm BA6849FP-Y 3-phase motor driver for cd-rom Datasheet

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
Pin descriptions
BA6849FP / BA6849FM
BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
BA6849FP-Y
865
Motor driver ICs
MA6849FS
866
BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
Motor driver ICs
BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
Input / output circuits
(1) Power save
(3)
Torque output (A1, A2, and A3)
(4)
Hall input (H1, H1–, H2, H2–, H3, H3–)
(2)
Torque command input
867
Motor driver ICs
BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
(5)
Hall bias
(7)
FR Output
(6)
FG output
(8)
Short brake
Note: Resistance values are typical values.
868
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
The RNF pin voltage with respect to the torque command
(EC) is as follows:
The I / O gain (GEC) from the EC pin to the RNF pin (output
current) is determined by the RNF detector resistor.
GEC = 0.255 / RNF [A / V]
The torque limit current ITL is given by:
ITL = 0.35 / RNF [A]
(3)
Reverse rotation detection function
The reverse detection circuit construction is shown in
Fig.11.
(1) Forward (EC < 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 (EC > ECR)
The phase relationship between the signals H2 and
H3 is opposite that for forward operation, and the reverse rotation detection circuit operates. The output
goes OFF, and becomes open circuit.
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
872
(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.
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 A1,
A2, and A3 coil outputs go open circuit. The thermal shutdown has approximately 15C of hysteresis.
Electrical characteristics curves
873
Motor driver ICs
External dimensions (Units: mm)
874
BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS
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