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Motor driver ICs
2-phase motor driver for VCR cylinder motors
BA6970FS
The BA6970FS is a direct-drive motor driver suitable for 2-phase, full-wave linear motors. The IC consists of a Hall amplifier control circuit, driver circuits, FG / PG signal amplifiers, and hysteresis amplifiers. FApplications VCR cylinder motors FFeatures 1) Linear drive system provides low switching noise. 2) Output current can be controlled by either current or voltage input. 3) Two amplifiers and two hysteresis amplifiers. FBlock diagram
4) Constant supply voltage pin for hall devices. 5) High ratio of output current and control current. (4000 typically) 6) Available in a compact surface-mount package.
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Motor driver ICs
FAbsolute maximum ratings (Ta = 25_C)
BA6970FS
FRecommended operating conditions (Ta = 25_C)
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Motor driver ICs
FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 12V)
BA6970FS
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Motor driver ICs
FPin descriptions
BA6970FS
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Motor driver ICs
FInput / output circuits (1) ECV (22 pin)
BA6970FS
(4)
I / O of amplifiers 1 and 2
Fig.1
(2)
Coil output (8, 6, 5, 3 pin)
Fig.4
(5)
I / O of hysteresis amplifiers
Fig.2
(3)
Hall inputs (9, 10, 11, 12 pin), ECI input
Fig.5
Note that the resistance values can vary 30%
Fig.3
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Motor driver ICs
FCircuit operation (1) The signal from the Hall device is amplified by the Hall amplifier and then supplied to the driver circuit. The driver gain, which is constant, is regulated by changing the Hall amplifier gain with the ECI input current or the ECV input voltage (ECI and ECV are output current control pins). The motor rotational speed is sensed by the FG, and the output from which is F / I-converted and supplied to the ECI pin or F / V-converted and supplied to the ECV pin as a feedback signal, so that a constant rotational speed is maintained as follows (Fig. 6) : (1) The motor speed decreases. (2) The speed control IC outputs a feedback signal (3) The Hall amplifier gain increases. (4) The output current increases. (5) The motor speed increases.
BA6970FS
(2) When the voltage on Hall IN1 ()) is higher than the voltage on Hall IN1 (*), an output current flows from OUT1 ()) to OUT1 (*) according to the voltage differential. When the voltage on Hall IN1 (*) is higher, on the other hand, an output current flows from OUT1 (*) to OUT1 ()). Similarly, when the voltage on Hall IN2 ()) is higher than the voltage on Hall IN2 (*), an output current flows from OUT2 ()) to OUT2 (*) according to the voltage differential. When the voltage on Hall IN2 (*) is higher, on the other hand, an output current flows from OUT2 (*) to OUT2 ()).
Fig.6
Fig.7
Fig.8
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Motor driver ICs
(3) Output waveforms are shown in Fig. 9. Because of the amplifier offset, the output is left OPEN when the output signal switches from positive to negative. The output waveform is determined by the external circuit because the IC impedance increases during this transition period. Since inductive loads are usually provided, a capacitor should be connected to suppress backlash voltages.
BA6970FS
FOperation notes (1) ECV input (pin 22) The ECV input is plotted against the output current in Fig. 10.
Fig.9
Fig.10
(2) Hall input Hall input signals of 50mV (peak to peak) or greater should be applied between pins 9 and 10 and between pins 11 and 12. The DC input range is 2V to (Vreg*1.5V). There will be no problem if the input is centered around Vreg / 2. Because the Hall input impedance is 1M or grater, any type of Hall device can be connected. No current flows when the transistor is off because pins 9 and 10 as well as pins 11 and 12 are differential inputs. Because the IC is a linear driver, any DC offset in the Hall device will be amplified and appear in the output. Use Hall devices having a minimum offset. Hall devices can be connected in either series or parallel.
Fig.11
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Motor driver ICs
(3) ECI input The ECI input circuit has 2VF and a 500 resistor connected in series. Current is limited only by the 500 resistor. (4) Amplifiers 1 and 2 An input range of 0.6V to (VCC*1.2V) is recommended. Unpredictable outputs may occur when the input is outside this range. (5) Hysteresis amplifier An input range of 0.6V to (VCC*1.2V) is recommended. Unpredictable outputs may occur when the input is outside this range. FApplication example
BA6970FS
(6) Thermal shutdown circuit The thermal shutdown circuit puts the driver outputs (8, 6, 5, 3 pin) to the open state at the temperature of 175_C (typical). The circuit is deactivated when the temperature drops to about 155_C. (7) Signal ground pin Pins 1 and 24 are signal ground pins. Be noted that unpredictable outputs may occur if your application causes a large current between pins 1 and 24 via the bonding wire IC chip.
Fig.12
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Motor driver ICs
FElectrical characteristic curves
BA6970FS
FExternal dimensions (Units: mm)
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