LB11826_08 Datasheet, PDF (10/11 Pages) Sanyo Semicon Device – For OA Products Three-Phase Brushless Motor Driver

LB11826
6. Speed lock range
The speed lock range is ±6.25% of the constant speed. If the motor speed falls inside the lock range, the LD pin goes to
“L” (open collector output). When the motor speed falls outside the lock range, the on-duty ratio of motor drive output
changes according to the speed error, causing control to keep the motor speed within the lock range.
7. PWM frequency
PWM frequency is determined from the capacity C (F) of capacitor connected to the PWM pin.
fPWM ≈ 1/ (14,400 × C)
It is recommended to keep the PWM frequency at 15k - 20kHz.
8. Hall input signal
The Hall input requires the signal input with an amplitude exceeding the hysteresis width (42mV max). Considering the
effect of noise, the input with the amplitude of 100mV or more is recommended.
9. F/R changeover
Motor rotation direction can be changed over with the F/R pin. When changing F/R while the motor is running, pay
attention to following points.
• For the through current at a time of changeover, the countermeasure is taken using a circuit. However, it is necessary
to prevent exceeding of the rated voltage (30V) due to rise of VCC voltage at a time of changeover (because the motor
current returns instantaneously to the power supply). When this problem exists, increase the capacity of a capacitor
between VCC and GND.
• When the motor current exceeds the current limit value after changeover, the lower-side Tr is turned OFF. But, the
upper-side Tr enters the short-brake condition and the current determined from the motor counter electromotive
voltage and coil resistance flows. It is necessary to prevent this current from exceeding the rated current (2.5A).
(F/R changeover at high motor speed is dangerous.)
10. Motor lock protection circuit
A motor lock protection circuit is incorporated for protection of IC and motor when the motor is locked.
When the LD output is “H” (unlocked) for a certain period in the start condition, the lower-side Tr is turned OFF. This
time is set with the capacity of the capacitor connected to the CSD pin. The time can be set to about 3.3 seconds with the
capacity of 10μF (variance about ±30%).
Set time (s) ≈ 0.33 × C (μF)
When the capacitor used has a leak current, due consideration is necessary because it may cause error in the set time,
etc.
Cancelling requires either the stop condition or re-application of power supply (in the stop condition). When the lock
protection circuit is not to be used, connect the CSD pin to GND.
When the stop period during which lock protection is to be cancelled is short, the charge of capacitor cannot be
discharged completely and the lock protection activation time at restart becomes shorter than the set value. It is
necessary to provide the stop time with an allowance while referring to the following equation. (The same applies to
restart in the motor start transient condition.)
Stop time (ms) ≥ 15 × C (μF)
11. Power supply stabilization
This IC has a large output current and is driven by switching, resulting in ready oscillation of the power line. It is
therefore necessary to connect a capacitor with a sufficient capacity between the VCC pin and GND for stabilization.
When a diode is inserted in the power line to prevent breakdown due to reverse connection of power supply, the power
line is particularly readily oscillated. The larger capacity need be selected.
12. Constant of integrating amplifier parts
Arrange the integrating amplifier external parts as near as possible to IC to protect them from noise effects. Arrange
them by keeping the largest possible distance from the motor.
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