BA6402F

Motor driver ICs 2-phase half-wave motor predriver BA6402F The BA6402F is a 2-phase, half-wave motor predriver suitable for fan motors. FFeatures 1) Lock detection and rotational speed sensing mechanisms are built in. 2) Hall constant current source is built in. FBlock diagram and application example 3) Compact 8-pin SOP package reduces the number of external components required. FAbsolute maximum ratings (Ta = 25_C) FRecommended operating conditions 689 Motor driver ICs FElectrical characteristics (unless otherwise noted, Ta = 25_C and VCC = 12V) BA6402F FRotational speed sensing and lock detection (6 pin) The circuit around pin 6 is described in Fig. 1. Normally, the C6 external capacitor is charging or discharging around the Hall signal when the motor is running. When the motor is locked, discharging does not occur at C6 because the Hall signal stops switching. Charging continues at C6 until the voltage increases to the pin-6 clamp voltage, and then Q1 turns ON to turn OFF the output. With the pin-6 current being constant (I6=6.8µA, typical), the time required after the motor is locked until the output current is turned OFF (duration between B and C in Fig. 2) is determined by the C6 capacitance. Toff=TBXC= (V6CL*VBEQ3) C6 I6 4VBE S C6 6.8µA (Typ.) 4.12 105 C6 (sec) (Typ.) where V6CL is pin-6 clamp voltage (nearly equal to 5VBE) For C6=2.2µF, for example, Toff is about 0.91s (typical). FOperation notes (1) Hall constant current source (3 pin, 6.8mA typically), which is directly connected with the IC bias circuit, is not available when pin 3 is OPEN (saturated). (2) Power dissipation The allowable power dissipation is plotted against ambient temperature in Fig. 3. FThermal derating curve 690 Motor driver ICs (3) Power dissipation The power consumed in the IC can be calculated from the following equation : PC=ΣPCn n=1 3 BA6402F (3) PC3 is power consumed by the output current. PC3=(VCC*VOH) IO VOH is the HIGH level voltage of pins 7 and 8. Power consumption can be reduced by raising the hFE-rank of the external output transistor and thereby reducing the IO value. Make sure that your application does not exceed the allowable power dissipation of the IC. (4) Restarting when motor is locked The outputs are turned OFF if the motor is stopped for some reason. To restart the motor from this situation, turn off the power first, fully discharge the pin 6 capacitor next, and then turn on the power again. (1) PC1 is power consumed by the circuit current. PC1=VCC ICC (2) PC2 is power consumed by the Hall current (pin 3). PC2=I3 V3 where V3=pin 3 voltage. Connecting a resistor between the VCC pin and pin 3 effectively reduces the IC current consumption. FElectrical characteristic curve FExternal dimensions (Units: mm) 691