LB11922_08 Datasheet, PDF (15/15 Pages) Sanyo Semicon Device – For OA Products Three-Phase Brushless Motor Driver

LB11922
14. VREG Pin
If a motor drive system is formed from a single power supply, the VREG pin (pin 1) can be used to create the
powersupply voltage (about 6.3V) for this IC. The VREG pin is a shunt regulator and generates a voltage of about 7V
by passing a current through an external resistor. A stable voltage can be generated by setting the current to value in the
range 0.2 to 1.5mA. The external transistors must have current capacities of at least 80mA (to cover the ICC + Hall bias
current + output current <source> requirements) and they must have voltage handling capacities in excess of the motor
power-supply voltage. Since the heat generated by these transistor may be a problem, heat sinks may be required
depending on the packages used. If the IC power-supply voltage (4.4 to 7.0V) is provided from an external circuit,
apply that voltage directly to the VCC pin (pin 30). In that case, the VREG pin must either be left open or connected to
ground.
15. FG Amplifier
The FG amplifier is normally implemented as a filter amplifier such as that shown in the application circuits to reject
noise. Since a clamp circuit has been added at the FG amplifier output, the output amplitude is clamped at about 3Vp-p,
even if the gain is increased.
Since a Schmitt comparator is inserted after the FG amplifier, applications must set the gain so that the amplifier output
amplitude is at least 250mVp-p. (It is desirable that the gain be set so that the amplitude is over 0.5Vp-p at the lowest
controlled speed to be used.)
The capacitor inserted between the FGIN+ pin (pin 20) and ground is required for bias voltage stabilization. To make
the connected capacitor as immune from noise as possible, connect this capacitor to the GND pin (pin 23) with a line
that is as short as possible.
16. Integrating Amplifier
The integrating amplifier integrates the speed error pulses and the phase error pulses and converts them to a speed
command voltage. At the same time it also sets the control loop gain and frequency characteristics using external
components.
17. NC pin
Since the NC pins are electrically open with respect to the IC itself, they can be used as intermediate connection points
for lines in the PCB pattern.
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PS No.7497-15/15