BA6444FP

Motor driver ICs 3-phase motor driver BA6444FP The BA6444FP is a 3-phase, full-wave, pseudo-linear motor driver suited for VCR capstan motors. The IC has a torque ripple cancellation circuit to reduce wow and flutter, and a forced brake circuit that allows abrupt change of operational mode. The output transistor saturation prevention circuit provides superb torque control over a wide range of current. FG and hysteresis amplifiers are also built in. FApplications VCR capstan motors, DAT capstan motors FFeatures 1) 3-phase, full-wave, pseudo-linear drive system. 2) Torque ripple cancellation circuit. 3) Forced brake circuit. 4) Output transistor (high- and low-sides) saturation prevention circuit. 5) FG and hysteresis amplifiers. 6) Thermal shutdown circuit. FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions 634 Motor driver ICs FBlock diagram BA6444FP 635 Motor driver ICs FPin descriptions BA6444FP 636 Motor driver ICs FInput / output circuits (1) I / O circuit interface Resistances, in Ω, are typical values. Note that the resistance values can vary "30%. 1) ED / S pin (2 pin) 2) BRK pin (3 pin) BA6444FP 3) Motor output (A1: 5 pin, A2: 6 pin, A3: 9 pin) 4) EC and ECR pins (10 pin, 11 pin) 5) TL pin (12 pin) 6) Hall signal input pins (H1): 27 pin, H1*: 26 pin, H2): 25 pin, H2*: 24 pin, H3): 23 pin, H3): 22 pin) 637 Motor driver ICs 7) Schmitt trigger amplifier I / O pins (17 pin, 16 pin) BA6444FP 8) Amplifier I / O pins (20 pin, 19 pin, 18 pin) 638 Motor driver ICs FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 5V, VM = 12V) BA6444FP 639 Motor driver ICs FCircuit operation (1) Pseudo-linear output and torque ripple cancellation The IC generates a trapezoidal (pseudo-linear) output current, whose waveform phase is 30 degrees ahead of that of the Hall input voltage (Fig. 9). BA6444FP The output current is sensed by applying the voltage developed across this resistor to the TL amplifier input as a feedback. The output current can be limited by adjusting the voltage applied to pin 12. The current is limited when pin 12 reaches the same potential as pin 7. The output current (IMAX.) under this condition is given by: IMAX. = VTL*(TL*RNF offset) RRNF The trapezoidal waveform of output current would create intermittence in the magnetic field generated by the 3-phase motor, and would result in an irregular rotation of the motor. To prevent this, the output waveform is obtained by superimposing a triangular wave on the trapezoidal wave (Fig. 10). This process is called torque ripple cancellation. (2) Torque control The output current can be controlled by adjusting the voltage applied to the torque control pins. where RRNF is the value of the resistor connected between the RNF and ground pins and VTL is the voltage applied to the TL pin. (4) Motor direction control (ED / S pin) The motor mode is: Forward when the ED / S-pin voltage is less than 0.9V, Stop when the voltage is between 1.3 X 3.0V, Reverse when the voltage is above 3.5V. In the stop mode, high- and low-side output transistors are turned off, resulting in a high impedance state. (5) Output transistor saturation prevention circuit This circuit monitors the output voltage and maintain the operation of the output transistors below their saturation levels. Operating the transistors in the linear characteristic range provides good control over a wide range of current and good torque characteristics even during overloading. The pins are the inputs to a differential amplifier. A reference voltage between 2.3-3.0V (2.5V recommended) is applied to pin 11. A brake is applied to the motor when the brake pin (pin 3) is put to LOW. The brake mode is activated when the brake pin voltage is 0.7V or less and deactivated when the voltage is 2.0V or more. (3) Output current sensing and torque limitation The RNF pin (pin 7) is the ground pin for the output stage. To sense the output current, a resistor (0.5Ω recommended) is connected between pin 7 and the ground. 640 Motor driver ICs (6) Ripple cancellation circuit The cancellation ratio of the torque ripple cancellation circuit (Fig. 10) can be adjusted by an external resistor connected to pin 1. Select a suitable value by taking wow and flutter into consideration. The ripple cancellation ratio can be obtained in the following manner. With EC = 2.7V, the RNF value for the Hall input of (H1), H2), H3)) = (L, L, H) is denoted as V1, and the RNF value for the Hall input of (H1), H2), H3)) = (L, M, H) is denoted as V2. The ripple cancellation ratio is then given by: RCC = V2*V1 (V1)V2) / 2 100 (%) BA6444FP (7) Brake pin The brake pin threshold depends on the chip temperature as shown in Fig. 16. Make sure that your application will work properly when using the IC at low or high temperatures. 641 Motor driver ICs FApplication example BA6444FP 642 Motor driver ICs FOperation notes (1) Thermal shut down circuit The BA6444FP has a thermal shutdown circuit to protect the IC. The shutdown temperatures is 175_C (typical) with a hysteresis width of 45_C (typical). When the circuit is activated due to an increased in chip temperature, the output pins (pins 5, 6 and 9) are set to the open state. The circuit is functional against excessive power dissipation, output short-circuiting, and other irregularities in the output current, but does not work against overheating caused by high internal currents due to externally caused IC damage or pin-to-pin short-circuiting. (2) The brake circuit has temperature-dependent thresholds as shown in Fig. 16. Make sure that your application will work properly when using the IC at low or high temperatures. (3) Be sure to connect the radiation fin to the ground. BA6444FP (4) Hall input The Hall input circuit is described in (6) of “I / O equivalent circuits.” Hall devices can be connected in either series or parallel. Be sure to keep the Hall input within the range of 1.5V to (VCC * 1.5V). (5) FG amplifier Note that unpredictable outputs may occur when the FG amplifier input is outside the recommended range. (6) ECGND pin (pin 4) Pin 4, a torque amplifier ground pin, should be connected to the ground. By connecting this pin to a point close to the motor ground, you can prevent the effect of GND common impedance on the current-sensing resistor (0.5Ω recommended) connected between RNF (pin 7) and the motor ground pin. FElectrical characteristic curves 643 Motor driver ICs BA6444FP FExternal dimensions (Units: mm) 644