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| Optical disc 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. FApplications CD-ROM, CD-R, CD-RW, DVD-ROM, and DVD-RAM FFeatures 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. FAbsolute maximum ratings (Ta = 25_C) 5) Built-in rotation direction detector. 6) Built-in reverse rotation prevention circuit. 7) Built-in short brake pin. 736 Optical disc ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS FRecommended operating conditions (Ta = 25_C) FBlock diagram 737 Optical disc ICs FPin descriptions BA6849FP / BA6849FM BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS BA6849FP-Y 738 Optical disc ICs MA6849FS BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS 739 Optical disc ICs FInput / output circuits (1) Power save BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS (2) Torque command input (3) Torque output (A1, A2, and A3) (4) Hall input (H1), H1-, H2), H2-, H3), H3-) 740 Optical disc ICs (5) Hall bias BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS (7) FR Output (6) FG output (8) Short brake Note: Resistance values are typical values. 741 Optical disc ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 5V, VM1 = 12V, VM2 = 12V) 742 Optical disc ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS FCircuit 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. 743 Optical disc 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. 744 Optical disc ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS (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. (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. FApplication example 745 Optical disc ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS FOperation 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 175_C, the A1, A2, and A3 coil outputs go open circuit. The thermal shutdown has approximately 15_C of hysteresis. FElectrical characteristics curves 746 Optical disc ICs BA6849FP / BA6849FP-Y / BA6849FM / BA6849FS FExternal dimensions (Units: mm) 747 |
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