LB11850VA Datasheet, PDF (11/14 Pages) Sanyo Semicon Device – Monolithic Digital IC For Fan Motor Single-Phase Full-Wave Pre-Driver with Speed Control Function

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(%)
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 = 4.1V
Next, obtain the resistances at which the voltage becomes 4.1V by dividing the resistance between CVO and GND
when CVO is 5V. The ratio of CVO-CVI: CVI-GND is 0.9V: 4.1V = 1: 4.5.
Based on the above, the resistance is 20kΩ between CVO and CVI and 91kΩ 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
CVO
R4
R5
C
CTL
VREF
CTL
No.A0609-11/14