LB11967V-TLM-H Datasheet, PDF (8/9 Pages) ON Semiconductor – For Variable Speed Fan Motor Single-Phase Full-Wave Pre-Driver

Control Timing Chart
LB11967V
VTH voltage
f=25kHz (CP=100pF)
ON-Duty-large
RMI voltage
CPWM
0V
ON-Duty-small
Rotation set to
minimum speed
(Stop mode)
PWM control variable speed
Low speed
High speed
VCC
0V
FG
4.55V
1.65V
PMW-IN disconnected
Full speed
12V
(1) Minimum speed setting (stop) mode
PWM-IN input is filtered to generate the VTH voltage. At low speed, the fan rotates with the minimum speed set with
RMI pin during low speed. If the minimum speed is not set (RMI = 6VREG), the fan stops.
(2) Low⇔High speed mode
PWM control is made through comparison of oscillation and VTH voltages with CPWM changing between
1.6V⇔4.6V.
When the VTH voltage is lower, the IC switches to drive mode. When the VTH voltage is higher, the p-channel FET
is turned off and coil current is regenerated through the low-side FET. Therefore, as the VTH voltage lowers, the
output ON-DUTY increases, increasing the coil current and raising the motor speed.
The rotation speed is fed back by the FG output.
(3) Full speed mode
The full-speed mode becomes effective with the VTH voltage of 1.65V or less. (VTH must be equal to GND when the
speed control is not to be made.)
(4) PWM-IN input disconnection mode
When the PWM-IN input pin is disconnected, VTH becomes 1.65V or les and the output enables full drive at 100%.
The fan runs at full speed. (Refer to the sample application circuit.)
No.8362-8/9