LB11850VA 데이터 시트보기 (PDF) - ON Semiconductor
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LB11850VA
ON Semiconductor
LB11850VA Datasheet PDF : 17 Pages
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LB11850VA
3. Additional Description of Operations:
The LB11850 forms a feedback loop inside the IC so that the FG period (motor speed) corresponding to the control
voltage is established by inputting the duty pulse.
LB11850VA
CTL
CTL
signal
Speed control block
FG
Closed
Feed−back
Loop
CONTROL
SIGNAL
Pre−driver block
Figure 6. Additional Description of Operations
The operation inside the IC is as follows. Pulse signals are created from the edges of the FG signals as shown in the figure
below, and a waveform with a pulse width which is determined by the CR time constants and which uses these edges as
a reference is generated by a one-shot multivibrator.
These pulse waveforms are integrated and the duty ratio of the pre-driver output is controlled as a control voltage.
FG
EDGE pulse
RC pin
Slope due to
CR time
constant
1 shot output
TRC(s) = 1.15RC
Figure 7. Pulse Waveforms
Furthermore, by changing the pulse width as determined by the CR time constant, the VCTL versus speed slope can be
changed as shown in the speed control diagram of the previous section.
However, since the pulses used are determined by the CR time constant, the variations in CR are output as-is as the speed
control error.
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