LB1860 データシートの表示（PDF） - ON Semiconductor

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LB1860

Two-Phase Half-Wave Variable Speed Fan Motor Driver

ON Semiconductor 

LB1860,1860M,1861,1861M

1 When a fan is rotating, the capacitor is charged at 4 µA (typ) and discharged through the C with pulses according to the

rotational speed.

2 When a fan is locked, no discharge occurs through the C and the C voltage rises, turning OFF the output at 0.8 × VIN.

3 When the output is turned OFF, discharge occurs through the C at 0.5 µA (typ). If the lock is not released when the C voltage

drops to VTH2, the capacitor is charged to VTH1 again. (At this moment, the output is turned ON.) These operations 2 and

3 repeated at a cycle of approximately ton : toff = 1:6 protect a motor.

4 If the lock is released when the C voltage drops to VTH2, the output is turned ON, starting rotation.

.(6) Rotation detect signal (RD pin)

Open collector output (Drive mode: ‘‘L’’, Stop mode: ‘‘H’’)

(7) Radio noise reducing (Pins B1, B2)

. Base pin of Darlington connection output transistor

. If radio noises need to be processed properly, the following actions should be taken:

1 Connect a capacitor of 0.01 µ to 0.1 µF between B1 and B2.

2 Connect a capacitor of 0.001 µ to 0.01 µF between OUT and B.

If output causes oscillation, add a resistor of 200 Ω to 1 kΩ in series with a capacitor.

.(8) Thermal shutdown function

Shutdown the driver output in case of coil short-circuiting and abnormal IC heating.

Thermistor-controlled Application Circuit Example

Figure 2

Output Timing Chart

Noise elimination

capacitor

Use of a thermistor enables motor speed to

be sensitive to the operating ambient

temperature.

The Rt pin voltage at Ta = 20 °C has

1.42 ms of ‘toff’ as calculated in expression

4 with the application constant of Figure 2.

However, the Rt pin voltage at Ta = 40 °C

is reduced into less than the Vct (= 1.3 V)

level, which results in a 0 of ‘toff’. This

means the 100% duty.

t = –C2 c R2 c 1n (VIN – VRt) ............. 4

VIN – VCt

( ): MFP14S

Unit (resistance: Ω, capacitance: F)

Hall input

Discharge pulse

Ct voltage

Output ‘off’ signal

OUT1 current

OUT2 current

All-phase ON waveform

Control output waveform

Figure 3

No.5

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