LB11852FV

No.A1112-11/12

〈LIM pin〉

The minimum speed is determined by the voltage of the LIM pin.

1) Obtain the ratio of the minimum speed required to the maximum speed.

Ra = Minimum/maximum speed … (1)

In the example shown in the figure above : Ra = minimum/maximum speed = 3000/10000 = 0.3

2) Obtain the product of the duty ratio at which the maximum speed is achieved and the value in formula (1).

Ca = Maximum speed duty ratio

× Ra … (2)

In the example given : Ca = maximum speed duty ratio

× Ra = 0.8 × 0.3 = 0.24

3) Obtain the required LIM pin voltage.

LIM = 5 - (3

× Ca) … (3)

In the example given : LIM = 5 - (3

× Ca) = 5 - (3 × 0.24) ≈ 4.3V

4) Divide the resistance of 5VREG to generate the LIM voltage.

In the example given, the voltage is 4.3V so the resistance ratio is 1 : 6.

The resistance is 10k

Ω between 5VREG and LIM and 62kΩ between LIM and GND.

(RPM)

Maximum speed

Minimum

speed setup

8000

10000

6000

4000

2000

0%

5V

100%

2V

CTL Duty(%)

CVO pin voltage (V)

VREF

LIM

5VREG

SOFT