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| BA6438S Motor driver ICs 3-phase motor driver BA6438S The BA6438S 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 an output transistor saturation prevention circuit that provides superb motor control over a wide range of current. The built-in motor power switching regulator allows applications with low power consumption !Applications 3-phase VCR capstan motors !Features 1) 3-phase, full-wave, pseudo-linear drive system. 2) Torque ripple cancellation circuit. 3) Reversal brake based on the detection of motor direction. 4) Output transistor (high-and low-sides) saturation prevention circuit 5) Motor power switching regulator with oscillation circuit. 6) Output-to-GND short-circuit detection. 7) Available in SDIP 24-pin power package (with radiation fins). !Absolute maximum ratings (Ta = 25C) Parameter Applied voltage Applied voltage Power dissipation Operating temperature Storage temperature Allowable output current Symbol VCC VM Pd Topr Tstg IOpeak Limits 7 24 2000 1 -10 +75 -40 +150 1.7 2 Unit V V mW C C A 1 2 Reduced by 16mW for each increase in Ta of 1C over 25C. Should not exceed the ASO value. !Recommended operating conditions (Ta = 25C) Parameter Operating power supply voltage Operating power supply voltage Symbol VCC VM Min. 4 3 Typ. 5 12 Max. 6 23 Unit V V BA6438S Motor driver ICs !Block diagram SIGNAL VCC MOTOR VCC CONTROL SIGNAL 11 MOTOR DIRECTION DET ED / S VCC 19 VM 24 H1+ Hall 10 9 Hall 8 7 Hall 6 5 4 PCH VCC 17 16 H1- H2+ H2- H3+ H3- MOTOR DIRECTION SETTING MOTOR DIRECTION SWITCHING Hall Amp. P SIGNAL COMBINER A1 23 A2 3 A3 AGC TSD 1 ATC 2 EC SHORT CIRCUIT DET. SWITCHING REGULATOR 13 14 REG VS ECR OSC 15 OUTPUT SATURATION OUTPUT RIPPLE SATURATION CANCELLATION 12 PCV PCI TL CS GND 20 22 18 21 OSC VCC TORQUE COMMAND BA6438S Motor driver ICs !Pin descriptions Pin No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Pin name Function Motor output Driver ground Motor output Hall amplifier AGC phase compensation Hall signal input Hall signal input Hall signal input Hall signal input Hall signal input Hall signal input Forward when LOW; stop when MEDIUM; reverse when HIGH Signal ground Switching regulator output (sink output) High-side saturation detection output Oscillator capacitor connection Torque control reference voltage input Torque control signal input Phase compensation for preventing driver high-side saturation Signal power supply Torque limiter Phase compensation for preventing driver low-side saturation Current sensing input Motor output Motor power supply A3 ATC A2 PCH H3 - H3 + H2 - H2 + H1 - H1 + ED / S GND REG VS OSC ECR EC PCV VCC TL PCI CS A1 VM !Electrical characteristics (unless otherwise noted, Ta = 25C, VCC = 5V, VM = 12V) Parameter Torque control input / output gain Ripple cancel ratio Output high level voltage Output low level voltage Oscillator frequency Saturation detection output gain Regulator current capacity Not designed for radiation resistance. Symbol Gio VRCC VOH VOL fOSC Gus IREGO Min. 0.25 4.6 1.1 0.95 100 5.0 30 Typ. 0.31 6.4 1.5 1.3 135 6.5 - Max. 0.36 7.2 1.9 1.65 160 8.0 - Unit - % V V kHz - mA VO = 5V Conditions EC = 2.22.1V, Input = L, L, H Input = L, L, HL, M, H IO = 0.8A IO = 0.8A C = 470pF - BA6438S Motor driver ICs !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. 1). . 30 Hall input Output current A brake is applied to the motor as described in the following.When the motor is running, pin 17 is given a negative potential with respect to the reference potential. If the pin 17 potential becomes positive, the IC detects the rise of pin 17 potential above the reference potential and activates the motor direction detecting circuit. The motor direction detecting circuit sends a signal to the motor direction setting circuit to reverse the motor direction. This causes a braking torque that depends on the pin 17 potential, so that the motor quickly reduces its speed. At the same time, the positive pin 17 potential is shifted to the reference potential, so that the motor stops smoothly. (3) Output current sensing and torque limitation Pin 2 is the ground pin for the output stage. To sense the output current, a resistor (0.5 recommended) is connected between pin 2 and the ground. The output current is sensed by applying the voltage developed across this resistor to pin 22 as a feedback. The output current can be limited by adjusting the voltage applied to pin 20. The current is limited when pin 20 reaches the same potential as pin 22. The output current (IMAX. ) under this condition is given by: V20P(TL-CSofs) R2P Fig. 1 The trapezoidal waveform of output current would create intermittence in the magnetic field generated by the 3phase 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. 2). This process is called torque ripple cancellation. IMAX.= Fig. 2 (2) Torque control and reversal brake The output current can be controlled by adjusting the voltage applied to the torque control pins (pins 16 and 17). These pins are the inputs to a differential amplifier. A reference voltage between 2.3 ~ 3.0V (2.5V recommended) is applied to pin 16. Output current Pin 16 reference voltage (2.5 V) where R2P is the value of the resistor connected between pin 2 and the ground, V20P is the voltage applied to pin 20, and (TL-CSofs ) is the offset between the TL and CS pins. VM 24pin 1pin ATC 2pin 3pin 23pin Offset Fig.4 Output circuit 0 Pin 17 voltage Dead zone (100 mV typically) Fig. 3 BA6438S Motor driver ICs (4) Motor direction control (pin 11) The motor mode is : Forward when the pin 11 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 characteristic range provides good control over a wide range of current and good torque characteristics even during overloading. 0 800mA Output current Output saturation voltage VM 24 HIGH level voltage monitor Oscillator Driver + 13 REG 15 OSC 14 VS Fig. 7 1.5V HIGH level voltage Fig.5 High level output voltage vs. output current (reference curves) LOW level voltage 1.3V Output saturation voltage ATC-pin voltage Output current 800mA 0 As shown in Fig. 7, the switch regulator circuit reduces the power consumed by the IC by reducing the collector-toemitter (C-E) voltage of the driver transistors. Nearly all the power dissipated by the IC is dissipated between the collectors and emitters of the output transistors. More power is consumed as the C-E voltage increases and as the output current increases. The output transistor C-E voltage is equal to the difference between the supply voltage and the voltage applied to the motor. Because the voltage across the motor decreases with decreasing drive current, the C-E voltage must increase if the supply voltage is fixed. Therefore, to improve the efficiency of the driver and to prevent the power rating of the IC being exceeded, the supply voltage must be varied in response to changes in the output current. The supply voltage is decreased at low current and increased at high current so that no excessive voltage is applied between the transistor collectors and emitters . (7) Output-to-ground short-circuit detection The motor output pins of the IC may be short-circuited to the ground by some fault conditions. A short-circuited output can destroy the output transistors because of excessive current, excessive voltage, or both. Even when a short-circuit condition does not completely destroy the device, it can still cause extreme overheating. To prevent this, the BA6438S contains a short-circuit detection circuit that turns off the motor drive current if the output-to-ground potential becomes abnormally low. HIGH level output voltage Fig.6 Low level output voltage vs. output current (reference curves) (6) Switching regulator The BA6438S has a switching regulator output pin. The IC outputs a PWM signal by comparing the output of the internal oscillator with the HIGH level output voltage monitored. LOW level output voltage BA6438S Motor driver ICs !Application example Motor direction control signal 11 Motor direction detection Signal power supply ED / S VCC 19 24 VM Motor power supply Motor direction setting H1+ Hall amp Motor direction switching Hall 10 H1- H2+ 23 A1 Hall 8 7 H2- H3+ P signal combiner 9 3 A2 Hall 6 5 H3- 4 PCH AGC 1 2 A3 ATC 0.5 REG TSD VCC 0.033 F EC 17 16 ECR Ripple cancellation Short-circuit detection Switching regulator 13 14 VS 0.1F Output saturation prevention Oscillator 12 GND VCC Output saturation detector TL 20 CS 22 PCV 18 PCI 21 15 OSC 0.033 F Torque control signal 0.1F 470PF Fig. 8 !Operation notes The BA6438S has two thermal shutdown circuits (TSD1 and TSD2) to protect the IC. The typical shutdown temperatures are 175C for TSD1 and 215C for TSD 2. When the TSD1 is activated at an elevated chip temperature, the output pins (pins 1, 3, and 23) are set to the open state. TSD1 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. When TSD2 is activated at a higher chip temperature, the high-and low-side output transistors are turned on, and the internal resistance between the motor power supply pin (pin 24) and the output ground pin (pin 2) drops to less than 3. The motor power supply current (IM) is then given by VM[V] IM= RM+R2P+3[] where IM is the motor supply current, VM is the motor supply voltage, RM is the motor power supply output resistance, R2P is the pin-2 resistance. In your application, make sure to connect between the motor power supply and pin 24 a circuit breaker that operates at currents less than IM . BA6438S Motor driver ICs !Electrical characteristic curves 0.7 0.6 ATC VOLTAGE : ATC (V) 160 VCC=5V, VM=12V, RATC=0.5 (H1+ , H2+ , H3+ ) = (LMH) ATC VOLTAGE : ATC (mV) 30 140 120 100 80 60 40 20 + (H1+ , H2+, H3 ) = (LLH) 0.5 0.4 0.3 0.2 0.1 0 0 (H1+ , H2+, H3+) = (LMH) ATC VOLTAGE : ATC (mV) VCC=5V VM=12V RATC=0.5 VCC=5V,VM=12V,RATC=0.5 (H1+ , H2+ , H3+) = (LMH) 25 20 15 10 5 0 -120 1.0 2.0 3.0 4.0 (V) 5.0 0 -800 -600 -400 -200 0 200 400 -80 -40 ECR +40 +80 TORQUE CONTROL : EC TORQUE CONTROL : EC (mV) (2.5V) TORQUE CONTROL : EC (mV) Fig.9 Output current vs. torque control voltage () Fig.10 Output current vs. torque control voltage () Fig.11 Output current vs. torque control voltage () 1.8 (V) 1.8 OUTPUT LOW VOLTAGE : VOL (V) 70 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 200 400 600 800 1000 HIGH level output voltage (1, 3, 23pin) 1.6 TL - CS OFFSET (mV) OUTPUT HIGH VOLTAGE : VOH 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 LOW level output voltage (1, 3, 23pin) 60 50 40 30 20 10 0 0 VCC=5V, VM=12V, RATC=0.5 EC=OV, ECR=2.5V ATC(2pin) Pin voltage (RATC = 0.5) 400 800 1200 0.2 0.4 0.6 OUTPUT CURRENT : IOH (mA) OUTPUT CURRENT : IOL (mA) TORQUE LIMIT VOLTAGE : TL(V) Fig.12 Output high level voltage vs. output current Fig.13 Output low level voltage vs. output current Fig.14 TL-CS offset vs. torque limit voltage 5 OSCILLATION FREQUENCY(Hz) 6 5 OUTPUT VOLTAGE (V) VCC=5V OUTPUT VOLTAGE (V) 1M 500k 300k 200k VCC=5V 4 Ec=2.3V 2V 1.5V 2 1.0V 0.5V 4 3 2 1 3 100k 50k 50 100 200 300 500 1000 VS 1 0 0 0.5 1.0 1.5 VM -VOH 2.0 (V) 2.5 3.0 0 10 20 30 40 50 60 OSC PIN CAPACITANCE(PF) SINK CURRENT(13pin) (mA) Fig.15 Capacitance of the capacitor connected to the OSC pin vs. oscillation frequency Fig.16 High-side saturation detection output voltage (pin 14) vs. output voltage Fig.17 Switching regulator sink current vs. output voltage BA6438S Motor driver ICs 3.0 POWER DISSIPATION : Pd (W) 2.5 2 1.5 1 0.5 0 0 40 80 120 160 AMBIENT TEMPERATURE : Ta(C) Fig.18 Thermal derating curve !External dimensions (Units : mm) 23.80.3 18.8 24 13 R1.8 0.51Min. 1 12 12.00.3 13.8 5.30.3 3.20.2 0.40.1 1.778 0.550.1 015 SDIP-M24 |
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