LB11867FV-TLM-E Datasheet, PDF (7/9 Pages) ON Semiconductor – For Fan Motor Variable Speed Single-phase Full-wave Pre-driver

LB11867FV
Control timing chart (Speed control)
VTH voltage
RMI voltage
f=30kHz (CP=220pF)
0V
FG
Minimum speed
setting rotation
(stop mode)
Low speed
High speed
PWM control speed variable
100%
ONDUTY
0%
3.0V
CPWM
1.1V
Full speed
(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.)
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