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Motor driver ICs
Fan motor driver IC
BA6817F / BA6818FS
The BA6817F and BA6818FS are 24V motor drivers for 2-phase, half-wave fan motors. The ICs have lock detection and automatic restart functions. In compact SOP8 (BA6817F) and SSOP-A16 (BA6818FS) packages, the ICs reduce the number of external components required. FApplications 2-phase motors such as fan motors FFeatures 1) Built-in power transistors. 2) Lock detection and automatic restart functions. 3) Thermal shutdown circuit. FAbsolute maximum ratings (Ta = 25_C)
4) Alarm output pin. (BA6817F / BA6818FS) 5) Hall signal output pin. (BA6818FS)
FRecommended operating conditions (Ta = 25_C)
717
Motor driver ICs
FBlock diagram
BA6817F / BA6818FS
FPin descriptions
718
Motor driver ICs
FHall input / output truth table
BA6817F / BA6818FS
FInput / output circuits
FElectrical characteristics (unless otherwise noted, Ta = 25_C)
719
Motor driver ICs
FCircuit operation The BA6817F and BA6818FS have motor lock detection and automatic restart circuits. The timing of lock detection and automatic restart is determined by the external capacitor connected to the LD pin. The charge time of the external capacitor is given by : ton (Charge time)= toff (Discharge time)= C S (VLDCL*VLDCP) ILDC C S (VLDCL*VLDCP) ILDD
BA6817F / BA6818FS
(Typical value) where VLDCL is the LD-pin clamp voltage (2.45V), (1.05V), VLDCP is the LD-pin comparator voltage (2.64A), ILDC is the LD-pin charge current (0.48A), ILDD is the LD-pin discharge current C is the capacitance of the LD-pin external capacitor. For C=0.47F, for example, the charge (output ON) and discharge (output OFF) times are 0.24s and 1.37s, respectively.
The timing chart for a motor lock occasion is shown in Fig. 1.
720
Motor driver ICs
FApplication example
BA6817F / BA6818FS
721
Motor driver ICs
FOperation notes (1) Thermal shutdown circuit The IC has a built-in thermal shutdown circuit. The is a temperature difference of 25_C (typical) between the temperatures at which the circuit is activated and deactivated.
BA6817F / BA6818FS
(3)
Hall amplifier input voltage
The circuit is activated at the temperature of about 175_C (typical), so that both output transistors are turned OFF. Normal operation resumes when the circuit is deactivated. (2) Power dissipation Power consumed in the IC can be calculated from the following equation : PC=PC1)PC2)PC3 PC1 is power consumed by the circuit current. PC1=VCZ ICC PC2 is the output stage current consumption. PC2=VOL IO VOL is the LOW level output voltage of output pins 1 and 2, and IO is the sink current of pins 1 and 2. PC3 is power consumed by the AL and HO pins. (The HO-pin is only for BA6818FS) where PC3=VALL IAL)VHOL IHO / 2 VALL is the AL-pin LOW level voltage, IAL is the AL-pin sink current, VHOL is the HO-pin LOW level voltage, IHO is the HO-pin sink current. Make sure that your application does not exceed the allowable power dissipation of the IC.
The R1 and R2 resistances must be set so as to maintain the Hall amplifier input bias voltage within the range of 0V to (VCZ*2V) including the signal amplitude. The Hall device may be affected by power supply noise due to the PCB conductor pattern. If you have this problem, insert a capacitor C1 as shown in Fig. 5. If the conductor lines from the Hall device output terminals to the Hall inputs of the IC are particularly long, noise can be picked up and fed into the inputs. If you have this problem, insert a capacitor C2 as shown in Fig. 5. Note that the Hall inputs have no hysteresis in this IC. Hall current is given by : VCZ R1)R2)RH
where RH is the Hall device impedance.
722
Motor driver ICs
FExternal dimensions (Units: mm)
BA6817F / BA6818FS
723

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