lv8105w ETC-unknow, lv8105w Datasheet - Page 20

• Manufacturer Part Number: lv8105w
• Description: For Variable Speed Control Three-phase Brushless Motor Predriver
• Manufacturer: ETC-unknow

14. Low-voltage protection circuit
15. Power supply stabilization
16. Ground lines
17. Integrating amplifier
18. FG amplifier
The LV8105W includes a low-voltage protection circuit to protect against incorrect operation when the V CC power is
applied or if the power supply voltage falls below its operating level. When the V CC voltage falls under the specified
voltage (VLVSD), all the outputs will be in the off state. If the V CC voltage rises to more than the hysteresis width
(∆VLVSD), the low-voltage protection function is cancelled.
Since this IC is used in applications that flow the large output current, the power supply line is subject to fluctuations.
Therefore, capacitors with capacitance adequate to stabilize the power supply voltage must be connected between the
V CC pin and GND. If diodes are inserted in the power supply line to prevent the IC destruction due to reverse power
supply connection, since this makes the power supply voltage even more subject to fluctuations, even larger
capacitance will be required.
The signal system GND and the output system GND must be separated, and connected to one GND at the connector. As
the large current flows to the output system GND, this GND line must be made as short as possible.
The integrating amplifier integrates the speed error pulses and phase error pulses and converts them to the speed
command voltage. At that time it also sets the control loop gain and the frequency characteristics. External components
of the integrating amplifier must be placed as close to the IC as possible to reduce influence of noise.
The FG amplifier normally makes up a filter amplifier to reject noise. Since a clamp circuit has been added at the FG
amplifier output, the output amplitude is clamped at about 3.2Vp-p, even if the amplifier gain is increased.
After the FG amplifier, the Schmitt comparator on one side hysteresis(200mV (typical)) is inserted. The Schmitt
comparator output (FGS output) becomes high level when the FG amplifier output is lower than the FGIN + voltage,
and becomes low level when the FG amplifier output is higher to more than Schmitt width as compared with the FGIN +
voltage. Therefore, it is desirable that the amplifier gain be set so that the output amplitude is over 1.0Vp-p at the lowest
controlled speed to be used.
The capacitor connected between the FGIN + pin and GND is required for bias voltage stabilization. This capacitor
must be connected to the GND1 pin (pin 45) with a line that is as short as possible to reduce influence of noise.
As the FG amplifier and the FGS output are operating even if the S/S pin is the stop state, it is possible to monitor the
motor rotation by the FGS output.
Output system GND : GND for Rf and V CC line capacitors
Signal system GND : GND for the IC and external components
LV8105W
No.A1271-20/21