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634 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. applications vcr capstan motors, dat capstan motors features 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. absolute maximum ratings (ta = 25 c) recommended operating conditions
635 motor driver ics BA6444FP block diagram
636 motor driver ics BA6444FP pin descriptions
637 motor driver ics BA6444FP input / output circuits (1) i / o circuit interface resistances, in w , are typical values. note that the resistance values can vary 30%. 1) ed / s pin (2 pin) 2) brk pin (3 pin) 3) motor output (a1: 5 pin, a2: 6 pin, a3: 9 pin) 4) e c and e cr 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)
638 motor driver ics BA6444FP 8) amplifier i / o pins (20 pin, 19 pin, 18 pin) 7) schmitt trigger amplifier i / o pins (17 pin, 16 pin)
639 motor driver ics BA6444FP electrical characteristics (unless otherwise noted, ta = 25 c, v cc = 5v, v m = 12v)
640 motor driver ics BA6444FP circuit 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). 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 ob- tained by superimposing a triangular wave on the trape- zoidal 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. the pins are the inputs to a differential amplifier. a refer- ence 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 r nf pin (pin 7) is the ground pin for the output stage. to sense the output current, a resistor (0.5 w recom- mended) is connected between pin 7 and the ground. the output current is sensed by applying the voltage de- veloped 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 (i max. ) under this condition is given by: where r rnf is the value of the resistor connected be- tween the r nf and ground pins and v tl is the voltage ap- plied 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 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 characteris- tic range provides good control over a wide range of cur- rent and good torque characteristics even during over- loading. r rnf i max. = v tl (tl r nf offset)
641 motor driver ics BA6444FP (6) ripple cancellation circuit the cancellation ratio of the torque ripple cancellation cir- cuit (fig. 10) can be adjusted by an external resistor con- nected to pin 1. select a suitable value by taking wow and flutter into consideration. the ripple cancellation ratio can be obtained in the fol- lowing manner. with e c = 2.7v, the r nf value for the hall input of (h1 , h2 , h3 ) = (l, l, h) is denoted as v1, and the r nf value for the hall input of (h1 , h2 , h3 ) = (l, m, h) is denoted as v2. the ripple cancellation ratio is then given by: (7) brake pin the brake pin threshold depends on the chip tempera- ture as shown in fig. 16. make sure that your application will work properly when using the ic at low or high tem- peratures. (v 1 v 2 )/2 r cc = v 2 v 1 100 (%)
642 motor driver ics BA6444FP application example
643 motor driver ics BA6444FP operation 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-cir- cuiting. (2) the brake circuit has temperature-dependent thresholds as shown in fig. 16. make sure that your ap- plication will work properly when using the ic at low or high temperatures. (3) be sure to connect the radiation fin to the ground. (4) hall input the hall input circuit is described in (6) of ai / o equivalent circuits.o hall devices can be connected in either series or parallel. be sure to keep the hall input within the range of 1.5v to (v cc 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 (0.5 w recommended) connected between r nf (pin 7) and the motor ground pin. electrical characteristic curves
644 motor driver ics BA6444FP external dimensions (units: mm)

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