lb11850va Sanyo Semiconductor Corporation, lb11850va Datasheet - Page 10

• Manufacturer Part Number: lb11850va
• Description: For Fan Motor Single-phase Full-wave Pre-driver With Speed Control Function
• Manufacturer: Sanyo Semiconductor Corporation

4) Procedure for calculating constants
<RC pin>
The slope shown in the speed control diagram is determined by the constant of the RC pin.
(1) Obtain FG signal frequency fFG (Hz) of the maximum speed of the motor.
(2) Obtain the time constant which is connected to the RC pin.
(3) Obtain the resistance and capacitance of the capacitor.
The temperature characteristics of the curve are determined by the temperature characteristics of the capacitor of the
RC pin. When temperature-caused fluctuations in the speed are to be minimized, use a capacitor with good
temperature characteristics.
(With FG2 pulses per rotation)
fFG (Hz) = 2 rpm/60 .... <1>
(Have “DUTY” (example: 100% = 1.0, 60% = 0.6) serve as the CTL duty ratio at which the maximum speed is to
be obtained.)
R×C = DUTY/(3.3×1.1×fFG) .... <2>
Based on the discharge capacity of the RC pin, the capacitance of the capacitor which can be used is 0.01 to
0.015µF. Therefore, find the appropriate resistance using equation <3> or <4> below from the result of <2>
above.
R = (R×C)/0.01µF .... <3>
R = (R×C)/0.015µF .... <4>
Motor
at maximum speed
(RPM)
0%
LB11850VA
CTL Duty(%)
100%
No.A0609-10/14