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Motor driver ICs
3-phase motor driver and reversible motor driver
BA6872AFM
The BA6872AFM has a 3-phase motor driver for VCR capstans, and a reversible motor driver for VCR loading. The capstan motor driver uses the three-phase, pseudo-linear drive method, and has a built-in torque ripple cancellation circuit, and an output transistor saturation prevention circuit. The loading motor driver has two logic inputs which are used to set the four operation modes (forward, reverse, stopped (idle) and brake. FApplications VCR capstan motors, VCR loading motors FFeatures 1) 3-phase, pseudo-linear drive system. 2) Torque ripple cancellation circuit. 3) Output transistor saturation prevention circuit. 4) Hall element power supply. FAbsolute maximum ratings (Ta = 25_C)
5) Two control logic inputs set the four operation modes: forward, reverse, stopped (idle), and brake. 6) Output voltage setting is possible using the Vref pin. 7) Thermal shutdown (TSD) circuit.
FRecommended operating conditions (Ta = 25_C)
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Motor driver ICs
FBlock diagram
BA6872AFM
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FPin descriptions
BA6872AFM
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Motor driver ICs
FInput / output circuits (1) Hall inputs (pins 1 to 6)
BA6872AFM
(4)
Torque control input (pins 10 and 11)
(2)
Rotation direction setting input (pin 7)
(5)
Torque limit (pin 12)
(3)
Hall element power supply (pin 9)
(6)
Logic input (pins 15 and 16)
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Motor driver ICs
(7) Loading motor output (pins 17 to 21)
BA6872AFM
(8)
Capstan motor output (pins 22 to 26)
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Motor driver ICs
FElectrical characteristics (unless otherwise noted, Ta = 25_C, VCC = 5V, VM1 = 14V, VM2 = 14V)
BA6872AFM
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FCircuit operation Capstan three-phase motor driver (1) Pseudo-linear output The IC generates a trapezoidal (pseudo-linear) output current whose waveform phase is 30 degrees ahead of that of the Hall input voltage.
BA6872AFM
(4) Motor direction control (ED / S pin) The motor mode is forward when the ED / S is voltage is less than 2.2V, and reverse when the ED / S is voltage is greater than 2.8V. (5) Output transistor saturation prevention circuit This circuit monitors the output voltage and maintains the operation of the output transistors below their saturation levels. Operating the transistors in the linear characteristic range provides good control over a wide current range, and good torque characteristics even during overload.
(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, and the reference voltage side is biased with a voltage of 2.2V (Typ.).
(3) Output current sensing and torque limiting ATC (pin 23) is the output stage ground. Connect a small resistor (0.5 recommended) between this pin and the GND pin, and feedback the voltage drop across this resistor to the TL AMP input to detect the output current.The output current can be limited by adjusting the voltage applied to TL (pin 12). The current is limited when pin 12 reaches the same potential as pin 23. The output current under this condition is given by: VTL - (TL - ATC offset) IMAX. = RATC where RATC is the value of the resistor connected between the RATC pin and ground, and VTL is the voltage applied to the TL pin.
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Motor driver ICs
Reversible motor driver for loading (6) Input block (FIN and RIN) and mode explanation These are the control signal input pins. The operations of the various modes are explained below. When FIN is high level, and RIN is low level, the mode is forward mode, and current flows from OUT1 to OUT2. When FIN is low level, and RIN is high level, the mode is reverse mode, and current flows from OUT2 to OUT1. When FIN and RIN are both high level, the mode is brake mode. In brake mode, the upper-side output transistor is off, and stops supply of current to the motor. The lowerside output transistor is on, and absorbs the back-rush of the motor and applies braking. When FIN and RIN are both low level, OUT1 and OUT2 are open-circuit potential, and the motor stops. FTruth table
BA6872AFM
(7) Vref pin (output high voltage setting pin) The output voltage can be varied by controlling Vref. VOH = Vref ) VBE (PNP) * VBE (NPN) ) (VOUT * Vref offset) ) IREF R1 However, Vref x VM2 * [Vsat (PNP) ) VBE (NPN)]
(8) Connection pins for output ground and output current sense resistor (RNF) By connecting a resistor to this pin, it is possible to sense the amount of current flowing in the motor. By adding an electronic governor, and controlling Vref, it is possible to construct a reversible motor driver.
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FApplication example
BA6872AFM
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FOperation notes (1) Thermal shutdown (TSD) The BA6872AFM has a thermal shutdown circuit to protect the IC. The shutdown temperature is 175 _C (Typ.) and the hysteresis width is 65_C (Typ.). When the circuit is activated due to an increase in the chip temperature, the output pins (pins 5, 6, and 9) are set to the open state. This 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 shorting. (2) Hall input The Hall input circuit is shown in (1) on the I / O circuits. Hall devices can be connected either in series or in parallel. Be sure to keep the Hall input within the range 1.5V to (VCC * 1.8V).
BA6872AFM
(3) Setting pin for the output high-level voltage (Vref) The voltage applied to the setting pin for the output highlevel voltage should not exceed the VM2 voltage. Connect this to VM2 when not using it. When the Vref pin is connected to a low impedance circuit for voltage setting, there is a chance that the output voltage may oscillate. When setting the voltage, set it via an impedance, or connect a capacitor between Vref and GND. The impedance and capacitor values will differ depending on the motor type, PCB pattern, and load current, so test the values using your actual circuit.
(4) GND The GND (pin 8) potential must be kept below that of the other pins at all times. The thermal dissipation FIN is internally connected to pin 8. Take care regarding handling of FIN. (5) Input pins Do not apply voltage to the inputs when VCC is not being supplied. Also, in the same way, even if VCC is being supplied, the inputs must be either at or below the VCC level. (6) Back-rush voltage The back-rush voltage will vary depending on the operating conditions, environment, and motor characteristics. Take care to ensure that the back-rush voltage does not interfere with the operation of the IC. (7) Large current lines Large currents flow in the power supply and GND lines of this IC. Therefore, depending on the PCB pattern layout and the values of external circuit components connected between the power supply and GND such as capacitors, this large current can be returned to the input, and cause incorrect operation and oscillation. To avoid this, carefully check the PCB layout and the values of all circuit components. (8) The power dissipation of the IC depends on how it is mounted. Perform thermal design carefully. (9) Power consumption The power dissipated by the IC varies widely with the applied voltage and output current. Pay close attention to the allowed power dissipation, and base your thermal design on the thermal resistance data and transient thermal resistance data to ensure that the ratings are not exceeded. (10) ASO Make sure that the output current and supply voltage do not exceed the ASO values. (11) Input mode switching To improve reliability, when switching modes, first switch to the open mode.
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Motor driver ICs
(12) This IC is not equipped with a circuit to limit in-rush current. Therefore, connect a current limiting resistor to limit the in-rush current. (13) Depending on the thermal dissipation conditions, power supply voltage, and type of motor, the potentials on the output pins of this IC can swing to levels well below GND, and cause faulty operation. In this case, take appropriate countermeasures such as connecting a diode between the outputs and GND. FExternal dimensions (Units: mm)
BA6872AFM
(14) Great care has been paid to the quality of this component. However, if the absolute maximum ratings for temperature and applied voltage are exceeded, the IC may be destroyed. Since it is not possible to predict whether the IC will be in the short mode or open mode if it is destroyed, be sure to use sufficient physical protective measures (fuses etc.) if there is a chance that the maximum ratings of the IC will be exceeded.
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