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LB11850VA-TLM-H Datasheet, PDF (13/14 Pages) ON Semiconductor – For Fan Motor Single-Phase Full-Wave Pre-Driver with Speed Control Function | |||
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LB11850VA
<LIM pin>
The minimum speed is determined by the voltage of the LIM pin.
(RPM)
Maximum speed 10000
8000
6000
4000
Minimum
speed setup 2000
0%
CTL Duty(%)
5V
CVO pin voltage (V)
100%
2V
(1) Obtain the ratio of the minimum speed required to the maximum speed.
Ra = Minimum speed/maximum speed .... <1>
In the example shown in the figure above, Ra = minimum speed/maximum speed = 3000/10000 = 0.3.
(2) Obtain the product of the duty ratio at which the maximum speed is obtained and the value in equation <1>.
Ca = Duty ratio at maximum speedÃRa .... <2>
In this example, Ca = duty ratio at maximum speedÃRa = 0.8Ã0.3 = 0.24.
(3) Obtain the required LIM pin voltage.
LIM = 5-(3ÃCa) .... <3>
In this example, LIM = 5-(3ÃCa) = 5-(3Ã0.24) â 4.3V.
(4) Divide the resistance of 5VREG, and generate the LIM voltage.
In this example, the voltage is 4.3V so the resistance ratio is 1: 6.
The resistance is 10kΩ between 5VREG and LIM and 62kΩ between LIM and GND.
5VREG
LIM
SOFT
CVI
VREF
No.A0609-13/14
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