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| Motor driver ICs 2-channel reversible motor driver BA6238A / BA6238AN / BA6239A / BA6239AN The BA6238A, BA6238AN, BA6239A, and BA6239AN are monolithic ICs incorporating two reversible-motor drivers that are suitable for driving small DC brush motors. The logic input section for controlling each motor can be easily connected with CMOSs and other control logic outputs. The torque during loading can be varied by controlling the voltage supplied to the motor with pin 8 of the output section. With a limited number of external parts, each driver has a function of two reversible-motor drivers. FApplications VCRs and audio tape recorders FFeatures 1) Two reversible-motor driver circuits are built in. (not operable at the same time) 2) Limited number of external parts. 3) Interface with CMOS devices. (protective resistor required when the CMOS output is higher than 5V) FBlock diagram 4) Built-in power transistor for motor driving. 5) Built-in thermal shutdown circuit. (the circuit brakes the output when the chip temperature is increased due to such an event as motor locking) 490 Motor driver ICs FAbsolute maximum ratings (Ta = 25_C) BA6238A / BA6238AN BA6238A / BA6238AN / BA6239A / BA6239AN BA6239A / BA6239AN FRecommended operating conditions (Ta = 25_C) BA6238A / 6238AN BA6239A / 6239AN 491 Motor driver ICs BA6238A / BA6238AN / BA6239A / BA6239AN FElectrical characteristics (unless otherwise noted, Ta = 25_C and VCC = 12V) BA6238A / BA6238AN BA6239A / BA6239AN 492 Motor driver ICs FMeasurement circuits BA6238A / BA6238AN / BA6239A / BA6239AN FApplication examples FInput / output truth table 493 Motor driver ICs BA6238A / BA6238AN / BA6239A / BA6239AN FCircuit operation (1) Input (pins 4, 5, and 6) These pins receive control logic signals. The relevant circuits are designed to have hysteresis and antinoise characteristics. The input circuit can control the logic by input currents of a few microamperes or more. The motor connected between pins 10 and 2 is selected when pin 4 is HIGH and pin 5 is LOW, while the motor connected between pins 10 and 3 is selected when pin 5 is HIGH and pin 4 is LOW. Pin 6 is the forward / reverse control input pin. (2) Output (pins 2, 3, and 10) Pin 10 is the common pin. Either pin 2 or 3 is left OPEN during motor driving. The waveform monitored on the OPEN pin will be the same as that on pin 10. (1) BA6238A / BA6238AN The output stage configuration of the BA6238A / BA6238AN is shown in Fig. 5. The output stage contains NPN transistors in a Darlington configuration, which means the saturation voltage between VCC1 and the output pin is rather high but the output voltage can be easily set by using a zener diode or a resistor voltage divider. The voltage on the VR pin can be varied from 0V to VCC1. The output voltage is at the maximum when pin 8 is OPEN. VBE (NPN Darlington) VOH=VCC1-Vsat (PNP)-2 VOL=Vsat (NPN Darlington) Vsat and VBE are functions of the output current (see Fig. 17). (2) BA6239A / BA6239AN The output configuration of the BA6239A / BA6239AN is shown in Fig. 6. Because the output stage contains only one NPN transistor, the saturation voltage between pin 8 and the output pin is about 0.7V less than that in the BA6238A. The output voltage is controlled by the pin-8 voltage. The voltage on the VR pin can be varied from 8V to VCC1. The output voltage is at the maximum when pin 8 is VCC1. VOH=VR-Vsat (PNP)-VBE (NPN) VOL=Vsat (NPN Darlington) Vsat and VBE are functions of the output current (see Fig. 18). (3) Output control (pin 8) Output voltage can be varied by controlling the pin-8 voltage. (1) BA6238A / BA6238AN The pin-8 voltage can vary from 0V to VCC. Because a constant current (0.6mA typically) flows out from pin 8, the output voltage can be controlled by using a zener diode or a resistor voltage divider. (2) BA6239A / BA6239AN In addition to controlling the output voltage, pin 8 supplies base current to the high-side output transistor (NPN). (4) Power supply (pins 7 and 9) Pin 7 supplies power to the input, logic, and thermal shutdown circuits. Pin 9 supplies power to the output transistors. (5) Thermal shutdown circuit Regardless of the input mode, the thermal shutdown circuit puts the outputs to LOW level when the chip temperature rises due to such an event as motor locking. When the thermal shutdown circuit is deactivated, the outputs revert to the status determined by input mode. The thermal shutdown circuit is activated when the chip temperature exceeds 150_C (125_C minimally), and deactivated when the chip temperature drops to 100_C (125_C maximally). The minimum temperature difference between the activation and deactivation settings is 10_C. (6) Ground pin and fins Pin 1 and the fins have the minimum potential within the IC. The PCB design should ensure that the common impedance is kept as low as possible when a large current flows. 494 Motor driver ICs BA6238A / BA6238AN / BA6239A / BA6239AN FOperation notes (1) Though the IC input pins can be directly connected with MOS output pins, it is recommendable to connect resistors of about 3 X 30k between the pins for the sake of pin protection (see Fig. 7). (2) When reversing the rotational direction of a motor, make sure to go through the brake mode in-between the opposite directions. It is recommendable to keep the brake mode for at least 10s. (3) Powering procedures should be designed so that VCC1 (pin 7) always rises first and falls last. (4) The quality of these products have been carefully checked; however, use of the products with applied voltages, operating temperatures, or other parameters that exceed the absolute maximum rating given may result in the damage of the IC and the product it is used in. If the IC is damaged, the short mode and open modes cannot be specified, so if the IC is to be used in applications where parameters may exceed the absolute maximum ratings, then be sure to incorporate fuses, or other physical safety measures. (5) Input pins Voltage should never be applied to the input pins when the VCC voltage is not applied to the IC. Similarly, when VCC is applied, the voltage on each input pin should be less than VCC and within the guaranteed range for the electrical characteristics. (6) Back-rush voltage Depending on the ambient conditions, environment, or motor characteristics, the back-rush voltage may fluctuate. Be sure to confirm that the back-rush voltage will not adversely affect the operation of the IC. (7) Large current line Large currents are carried by the motor power supply and motor ground for these ICs. Therefore, the layout of the pattern of the PC board and the constants of certain parameters for external components, such as the capacitor between the power supply and ground, may cause this large output current to flow back to the input pins, resulting in output oscillation or other malfunctions. To prevent this, make sure that the PC board layout and external circuit constants cause no problems with the characteristics of these ICs. (8) Power dissipation The power dissipation will fluctuate depending on the mounting conditions of the IC and the ambient environment. Make sure to carefully check the thermal design of the application where these ICs will be used. (9) Power consumption The power consumption by the IC varies widely with the power supply voltage and the output current. Give full consideration to the power dissipation rating and the thermal resistance data and transient thermal resistance data, to provide a thermal design so that none of the ratings for the IC are exceeded. (10) ASO Make sure that the output current and supply voltage do not exceed the ASO values. (11) Precautions for input mode switching To ensure reliability, it is recommended that the mode switching for the motor pass once through the open mode. (12) Factors regarding the thermal, power supply, and motor conditions If the potential of the output pin sways greatly and goes below the potential of ground, the operation of the IC may malfunction or be adversely affected. In such a case, place a diode between the output and ground, or other measure, to prevent this. 495 Motor driver ICs FElectrical characteristic curves BA6238A / BA6238AN / BA6239A / BA6239AN 496 Motor driver ICs BA6238A / BA6238AN / BA6239A / BA6239AN FExternal dimensions (Units: mm) 497 |
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