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. Applications VCR cylinder motors Features 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. Block diagram 594 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. Motor driver ICs BA6970FS FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions (Ta = 25_C) 595 Motor driver ICs FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 12V) 596 BA6970FS Motor driver ICs BA6970FS Pin descriptions 597 Motor driver ICs Input / 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.3 598 Motor driver ICs BA6970FS Circuit 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. (2) When the voltage on Hall INφ1 () is higher than the voltage on Hall INφ1 (), an output current flows from OUT1 () to OUT1 () according to the voltage differential. When the voltage on Hall INφ1 () is higher, on the other hand, an output current flows from OUT1 () to OUT1 (). Similarly, when the voltage on Hall INφ2 () is higher than the voltage on Hall INφ2 (), an output current flows from OUT2 () to OUT2 () according to the voltage differential. When the voltage on Hall INφ2 () is higher, on the other hand, an output current flows from OUT2 () to OUT2 (). Fig.6 Fig.7 Fig.8 599 Motor driver ICs BA6970FS (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. Operation 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 (Vreg1.5V). There will be no problem if the input is centered around Vreg / 2. Because the Hall input impedance is 1MΩ 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.11 600 Motor driver ICs BA6970FS (3) ECI input The ECI input circuit has 2VF and a 500Ω resistor connected in series. Current is limited only by the 500Ω resistor. (4) Amplifiers 1 and 2 An input range of 0.6V to (VCC1.2V) is recommended. Unpredictable outputs may occur when the input is outside this range. (5) Hysteresis amplifier An input range of 0.6V to (VCC1.2V) is recommended. Unpredictable outputs may occur when the input is outside this range. (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. FApplication example Fig.12 601 Motor driver ICs Electrical characteristic curves External dimensions (Units: mm) 602 BA6970FS