Motor driver ICs 2-phase motor driver for VCR cylinder motors BA6825FS / BA6826FS The BA6825FS and BA6826FS are direct-drive motor drivers suitable for 2-phase, full-wave linear motors. They consist of a Hall amplifier control circuit and driver circuits. Applications VCR cylinder motors Features 1) Linear drive system provides low switching noise. 2) Constant supply voltage pin for hall devices. 3) High ratio of output current against control current. (4000 Typ.) Block diagram 580 4) Available in compact surface-mount packages. Motor driver ICs BA6825FS / BA6826FS FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 12V) FPin descriptions 581 Motor driver ICs Input / output circuits (1) Hall and ECI inputs 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 input current on the output current control pin (ECI pin). The motor rotational speed is sensed by the FG, and the output of which is F / I-converted and supplied to the ECI pin as a feedback signal, so that a constant rotational speed is maintained as follows : (1) The motor speed decreases. (2) The speed control IC outputs a feedback signal to the ECI pin. (3) The Hall amplifier gain increases. (4) The output current increases. (5) The motor speed increases. 582 BA6825FS / BA6826FS (2) Coil output (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 (). Motor driver ICs BA6825FS / BA6826FS (3) Output waveforms are shown in Fig. 5. 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 the backlash voltage. FOperation notes (1) ECI input The ECI input circuit has 2VF and a 500Ω resistor connected in series. Current is limited only by the 500Ω resistor. (2) Hall input Signals of 50mV (peak to peak) or greater should be applied to the Hall device input. The DC input range is between 2V and (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 the Hall input pins ( and ) are differential. Because the ICs are linear drivers, 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. (3) Thermal shutdown circuit The circuit puts the driver outputs (9, 11, 12, and 14 pin) to the open state at the temperature of 175_C (typical). There is a temperature difference of about 20_C between the temperatures at which the circuit is activated and deactivated. 583 Motor driver ICs Application examples 584 BA6825FS / BA6826FS Motor driver ICs BA6825FS / BA6826FS Electrical characteristic curves External dimensions (Units: mm) 585