LB11852FV Datasheet, PDF (11/12 Pages) Sanyo Semicon Device – Monolithic Digital IC For Fan Motor Single-phase Full-wave Pre-driver with Speed Control Function

LB11852FV
〈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/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 10kΩ between 5VREG and LIM and 62kΩ between LIM and GND.
5VREG
LIM
SOFT
VREF
No.A1112-11/12