LB11867FV

No.A0195-7/9

Control timing chart (Speed control)

(1) Minimum speed setting (stop) mode

The low-speed fan rotation occurs at the minimum speed set with the RMI pin. When the minimum speed is not set

(RMI pin pulled up to 5VREG), the motor stops.

(2) Low speed

⇔high speed

PMW control is made by comparing the CPWM oscillation voltage (1.1V

⇔3.0V) and VTH voltage.

Both upper and lower output TRs are turned ON when the VTH voltage is low. The upper output TR is turned OFF

when the VTH voltage is high, regenerating the coil current in the lower TR. Therefore, as the VTH voltage decreases,

the output ON-DUTY increases, causing increase in the coil current, raising the motor rotation speed.

The rotation speed can be monitored with the FG output.

(3) Full speed mode

The full speed mode becomes effective when the VTH voltage is 1.1V or less. (Set VTH = GND when the speed

control is not to be made.)

0V

3.0V

1.1V

CPWM

f=30kHz (CP=220pF)

0%

100%

FG

ONDUTY

VTH voltage

RMI voltage

Minimum speed

setting rotation

(stop mode)

Low speed

High speed

PWM control speed variable

Full speed