Rohm BA6858AFP Three-phase motor driver for cd-rom Datasheet

Motor driver ICs
Three-phase motor driver for
CD-ROMs
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
The BA6858A and BA6859A series are ICs developed for CD-ROM spindle motor drives. In addition to the functions
of the BA6849 series, (short brake, reverse-rotation prevention circuit, rotation direction dector, and FG output), the
BA6858A and BA6859A series have a built-in brake mode switching pin. With torque command input, these series are
compatible with the DSP3.3V. In addition, the BA6858A series has an FG composite output.
Applications
CD-ROM, CD-R, CD-RW, DVD-ROM, and DVD-RAM
Features
1) Three-phase, 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.
Absolute maximum ratings (Ta = 25C)
848
6)
7)
8)
9)
Built-in reverse rotation prevention circuit.
Built-in short brake pin.
Built-in brake mode switching pin.
DSP3.3V compatible.
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Motor
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BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
Recommended operating conditions (Ta = 25C)
Block diagram
BA6858AFP / BA6858AFM
849
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Pin descriptions
BA6858AFP / BA6858AFM
850
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
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BA6859AFP / BA6859AFM
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
BA6859AFP-Y
851
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BA6859AFS
852
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
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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
853
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
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(5)
Hall bias
(7)
FG2 Output
(6)
FG output
(8)
FR output
(9)
Short brake
854
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Motor
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BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
(10) Brake mode
Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 5V, VM = 12V)
855
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856
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
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Motor
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BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
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.11. 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.
857
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Motor
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BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
(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 = 0.35 / 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.13.
(1) Forward (EC < ECR)
The phase relationship between the Hall input signals
H2 and H3 becomes as shown in Fig.11, 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.
858
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(4) Short brake
When 2.5V or more is applied to the short brake pin, the
top-side output transistors of all phases go off, and the
bottom-side output transistors go on. This applies braking to the motor. Short braking operates regardless of the
torque command signal.
(5) Brake mode switching
When 2.5V or more is applied to the BR pin, the brake
mode for when EC > ECR can be changed.
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
(6) Power save
When 2.5V or more is applied to the power save pin, all
circuits are on. When 1.0V or less is applied, the IC enters power save mode, and functions only for surpressing
power consumption.
Application example
859
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
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Operation notes
(1) Torque command
When operating with ECR = 2.5V, the voltage range for the
torque command input is 0.5V to 3.3V, and therefore, the
characteristic will be unbalanced as shown in Fig.15.
Take due care.
(2) Switches
The switches have a temperature characteristic of
approximately –5mV / C. Take care with regard to the
input voltage range.
(3) 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.
Set the Hall input voltage in the range 1.0V to 4.0V.
Set the resistance values between VH and VCC pins and the Hall elements after calculating the current to flow in Hall
elements.
If there will not be a resistor connected between the Hall elements and the VH pin, we recommend that IVH = 5mA or more.
(4) Thermal shutdown (TSD)
When the junction temperature reaches 175C (Typ.), the A1, A2, and A3 coil outputs go open circuit.
The thermal shutdown has approximately 15C (Typ.) of hysteresis.
860
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Motor
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BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
Electrical characteristics curves
861
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External dimensions (Units: mm)
862
BA6858AFP / BA6858AFM / BA6859AFP /
BA6859AFP-Y / BA6859AFM / BA6859AFS
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