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821 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 cap- stan 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. applications vcr capstan motors, vcr loading motors features 1) 3-phase, pseudo-linear drive system. 2) torque ripple cancellation circuit. 3) output transistor saturation prevention circuit. 4) hall element power supply. 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. absolute maximum ratings (ta = 25 c) recommended operating conditions (ta = 25 c)
822 motor driver ics BA6872AFM block diagram
823 motor driver ics BA6872AFM pin descriptions
824 motor driver ics BA6872AFM input / output circuits (1) hall inputs (pins 1 to 6) (2) rotation direction setting input (pin 7) (5) torque limit (pin 12) (3) hall element power supply (pin 9) (4) torque control input (pins 10 and 11) (6) logic input (pins 15 and 16)
825 motor driver ics BA6872AFM (7) loading motor output (pins 17 to 21) (8) capstan motor output (pins 22 to 26)
826 motor driver ics BA6872AFM electrical characteristics (unless otherwise noted, ta = 25 c, v cc = 5v, v m 1 = 14v, v m 2 = 14v)
827 motor driver ics BA6872AFM circuit 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. (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 w recommended) between this pin and the gnd pin, and feedback the voltage drop across this re- sistor to the tl amp input to detect the output cur- rent.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: where ratc is the value of the resistor connected be- tween the ratc pin and ground, 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 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 characteris- tic range provides good control over a wide current range, and good torque characteristics even during over- load. v tl (tl atc offset) r atc i max. =
828 motor driver ics BA6872AFM reversible motor driver for loading (6) input block (f in and r in ) and mode explanation these are the control signal input pins. the operations of the various modes are explained below. when f in is high level, and r in is low level, the mode is forward mode, and current flows from out1 to out2. when f in is low level, and r in is high level, the mode is reverse mode, and current flows from out2 to out1. when f in and r in 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 lower- side output transistor is on, and absorbs the back-rush of the motor and applies braking. when f in and r in are both low level, out1 and out2 are open-circuit potential, and the motor stops. truth table (7) vref pin (output high voltage setting pin) the output voltage can be varied by controlling vref. v oh = vref v be (pnp) v be (npn) (v out vref off- set) iref r1 however, vref v m 2 [v sat (pnp) v be (npn)] (8) connection pins for output ground and output cur- rent 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.
829 motor driver ics BA6872AFM application example
830 motor driver ics BA6872AFM operation notes (1) thermal shutdown (tsd) the BA6872AFM has a thermal shutdown circuit to pro- tect 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 ex- cessive power dissipation, output short-circuiting, and other irregularities in the output current, but does not work against overheating caused by high internal cur- rents 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 paral- lel. be sure to keep the hall input within the range 1.5v to (v cc 1.8v). (3) setting pin for the output high-level voltage (vref) the voltage applied to the setting pin for the output high- level voltage should not exceed the v m 2 voltage. con- nect this to v m 2 when not using it. when the vref pin is connected to a low impedance cir- cuit for voltage setting, there is a chance that the output voltage may oscillate. when setting the voltage, set it via an impedance, or con- nect a capacitor between vref and gnd. the impedance and capacitor values will differ depend- ing 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 in- ternally connected to pin 8. take care regarding handling of fin. (5) input pins do not apply voltage to the inputs when v cc is not being supplied. also, in the same way, even if v cc is being sup- plied, the inputs must be either at or below the v cc level. (6) back-rush voltage the back-rush voltage will vary depending on the operat- ing 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 lay- out and the values of external circuit components con- nected between the power supply and gnd such as ca- pacitors, 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 ap- plied voltage and output current. pay close attention to the allowed power dissipation, and base your thermal de- sign on the thermal resistance data and transient thermal resistance data to ensure that the ratings are not exceed- ed. (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.
external dimensions (units: mm) 831 motor driver ics BA6872AFM (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 ap- propriate countermeasures such as connecting a diode between the outputs and gnd. (14) great care has been paid to the quality of this com- ponent. 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 protec- tive measures (fuses etc.) if there is a chance that the maximum ratings of the ic will be exceeded.
appendix appendix1-rev1.0 the products listed in this document are designed to be used with ordinary electronic equipment or devices (such as audio visual equipment, office-automation equipment, communications devices, electrical appliances and electronic toys). should you intend to use these products with equipment or devices which require an extremely high level of reliability and the malfunction of with would directly endanger human life (such as medical instruments, transportation equipment, aerospace machinery, nuclear-reactor controllers, fuel controllers and other safety devices), please be sure to consult with our sales representative in advance. notes no technical content pages of this document may be reproduced in any form or transmitted by any means without prior permission of rohm co.,ltd. the contents described herein are subject to change without notice. the specifications for the product described in this document are for reference only. upon actual use, therefore, please request that specifications to be separately delivered. application circuit diagrams and circuit constants contained herein are shown as examples of standard use and operation. please pay careful attention to the peripheral conditions when designing circuits and deciding upon circuit constants in the set. any data, including, but not limited to application circuit diagrams information, described herein are intended only as illustrations of such devices and not as the specifications for such devices. rohm co.,ltd. disclaims any warranty that any use of such devices shall be free from infringement of any third party's intellectual property rights or other proprietary rights, and further, assumes no liability of whatsoever nature in the event of any such infringement, or arising from or connected with or related to the use of such devices. upon the sale of any such devices, other than for buyer's right to use such devices itself, resell or otherwise dispose of the same, no express or implied right or license to practice or commercially exploit any intellectual property rights or other proprietary rights owned or controlled by rohm co., ltd. is granted to any such buyer. products listed in this document use silicon as a basic material. products listed in this document are no antiradiation design. about export control order in japan products described herein are the objects of controlled goods in annex 1 (item 16) of export trade control order in japan. in case of export from japan, please confirm if it applies to "objective" criteria or an "informed" (by miti clause) on the basis of "catch all controls for non-proliferation of weapons of mass destruction.

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