LB8503V Datasheet, PDF (10/20 Pages) Sanyo Semicon Device – Monolithic Digital IC DC Fan Motor Speed Control IC

LB8503V
[CVO and CVI Pins]
These pins determine the origin of the slope. (To set the origin to 0% at 0 rpm, short CVO to CVI.)
1. X axis shift (Resistor dividing the CVO to ground potential)
(RPM)
Motor
full speed
X axis shift
0%
100%
CTL Duty (%)
To shift the characteristics from a 0% = 0 rpm origin to a situation where the speed at a duty of 30% is shifted to 0%:
First, determine the required CVI pin input voltage at 0%.
CVI = 6 - (4 × DUTY) = 6 - (4 × 0.3) = 6 - 1.2 = 4.8V
Next, when CVO is 6V, determine the resistor values for the resistor divider between CVO and ground such that the
midpoint becomes 4.8V.
CVO - CVI : CVI - ground = 1.2V : 4.8V = a ratio of 1 : 4.
From the above, the desired resistor values will be 20kΩ between CVO and CVI and 80kΩ between CVI and ground.
Note that the slope will change. (In this case, since the resistor ratio is 1:4, the result will be 4/5 of (or 0.8 times) the
original slope.)
If required, the RC pin resistor value must be changed to correct the slope.
LIM
SOFT
CVI
CVO
R4
R5
C
CTL
VREF
CTL
ILB01773
No.A0366-10/20