LB11961-W-AH(2016) データシートの表示（PDF） - ON Semiconductor
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LB11961-W-AH Datasheet PDF : 8 Pages
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LB11961
*6. FG output
This is an open collector output, and a rotation count detection function can be implemented using this FG output, which
corresponds to the phase switching. This pin must be left open if unused.
*7. HB pin
This pin provides a Hall effect sensor bias constant-voltage output of 1.25V.
*8. RMI pin
Connect this pin to VTH if unused. Even if unused, the IC is set internally to operate at a 10% drive duty at the voltage
corresponding to the lowest speed. (The capacitor is used to set up full-speed mode at startup.)
Control Timing Chart
(VCC 28%)
Internal lowest speed setting voltage
f = 25kHz (CP=100pF)
RMI voltage
High on duty
THERMISTOR
REMOVED
3.6V
(VCC 30%)
CPWM
0V
VCC
Low on duty
Set minimum
speed
PWM control variable speed mode
Low
temperature
2.0V
(VCC 16%)
Full speed mode
High
temperature
12V
0V
FG
1. Set minimum speed mode
A VTH voltage level is generated when the thermistor detects the set temperature. At low temperatures, the fan
motor turns at the lowest speed, which is set with the RMI pin. The LB11961 compares the CPWM oscillator
voltage with the RMI pin voltage and sets the duty for the lowest drive state.
2. High speed low speed mode
The PWM signal is controlled by comparing the CPWM oscillation voltage that cycles between 1.2V and 3. 8V and
the VTH voltage.
When the VTH voltage is lower, the high and low side transistors are turned on, and when the VTH voltage is higher,
the high side transistor is turned off and the coil current is regenerated through the low side transistor. Thus the
output on duty increases as the VTH voltage becomes lower, the coil current increases, and the motor speed
increases.
Rotation speed feedback is provided by the FG output.
3. Full-speed mode
The LB11961 switches to full-speed mode above a certain temperature.
4. Thermistor removed mode
If the thermistor is removed, the VTH input voltage will rise. However, the output will go to full drive at 100% and
the motor will run at full speed.
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