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LB11850VA-TLM-E

Single‐phase Full‐wave Pre‐driver with Speed Control Function for Fan Motor

ON Semiconductor 

LB11850VA

<CVO, CVI Pins>

These pins determine the position of the slope origin. (When the origin point is at (0%, 0 rpm), CVO and CVI are shorted.)

1) Movement along the X-axis (resistance divided between CVO and GND)

(RPM)

Motor

at maximum speed

Move in the direction

of the X−axis

0%

CTL Duty(%)

Figure 9.

100%

(Example)

In the case where the characteristics change from ones with the origin point (0%, 0 rpm) to ones where the speed at a duty

ratio of 30% becomes the speed at 0%:

First, obtain the input voltage of the CVI pin required at 0%.

CVI = 5 − (3 × duty ratio) = 5 − (3 × 0.3) = 5 − 0.9 = 4.1 V

Next, obtain the resistances at which the voltage becomes 4.1 V by dividing the resistance between CVO and GND when

CVO is 5 V. The ratio of CVO−CVI: CVI−GND is 0.9 V : 4.1 V = 1 : 4.5.

Based on the above, the resistance is 20 kW between CVO and CVI and 91 kW between CVI and GND.

Furthermore, the slope changes. (In the case of the example given, since the resistance ratio is 1 : 4.5, the slope is now

4.5/5.5 = 0.8 times what it was originally.)

If necessary, change the resistance of the RC pin, and adjust the slope.

LIM

SOFT

CVI

R4

CVO

R5

VREF

C

CTL

CTL

Figure 10.

www.onsemi.com

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