LB1924 データシートの表示（PDF） - SANYO -> Panasonic
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LB1924 Datasheet PDF : 11 Pages
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LB1924
• External clock (A frequency equivalent to the crystal oscillator frequency: 1 to 10 MHz)
— If a frequency equivalent to a crystal oscillator frequency is input from an external source, input that signal through
a series resistor of about 13 kΩ to the XI pin. The XO pin should be left open.
Input signal levels:
Low-level voltage: 0 to 0.8 V
High-level voltage: 2.5 to 5.0 V
5. Speed lock range
The speed lock range is ±6.25% of the set speed. When the motor speed is in the lock range the LD pin will go low
(open collector output). The IC controls the motor speed by changing the motor drive output on duty according to the
speed error signal if the motor speed goes outside the lock range.
6. PWM frequency
The PWM frequency is determined by the capacitor and resistor connected to the CR pin.
fPWM ≈ 1/(0.5 × C × R)
A PWM frequency in the range 15 to 25 kHz is desirable. If the PWM frequency is too low, the motor may resonate
at the PWM frequency when locked resulting in noise, since that frequency will be in the audible range. If the PWM
frequency is too high, the switching loss in the output transistor will increase. The value of the resistor must be over 5
kΩ.
7. Hall input signals
The signals input as the Hall inputs must have amplitudes that exceed the hysteresis, which has a maximum value of
24 mV. Considering noise, inputs with amplitudes of at least 100 mV are desirable. Attach a noise rejection capacitor
(around 0.001 to 0.01 µF) across the IN3 Hall input (pins 26 and 27). Since these pins are adjacent to the OUT1
output pin, noise in this input may cause disturbances in the output waveforms.
8. F/R switching
The F/R pin can be used to change the direction of motor rotation. However the following points must be observed
when designing applications that will change the motor direction while the motor is turning.
• Application circuit must be designed to handle the through current that occurs when the direction is switched.
However, increases in the VCC voltage during switching due to motor current flowing into the power supply system
instantaneously, must not exceed the rated voltage (30 V) of the device. Increase the value of the capacitor between
power supply and ground if this is a problem.
• If the motor current after switching exceeds the current limiter upper limit, the lower side transistor will be turned
off. However, the high side transistor will go to the short braking state, and a current determined by the motor reverse
voltage and the coil resistance will flow in this transistor. Applications must be designed so that this current does not
exceed the rated current, 3.1 A. In general, switching the direction with the F/R pin at high motor speeds is
dangerous.
9. Lock protection circuit
This IC includes a built-in lock protection circuit to protect the IC and the motor when the motor is locked. In the
start state, if the LD output remains high for a fixed period (the unlocked state), the lower side transistor is turned off.
The capacitance of the capacitor connected to the CROCK pin sets this time. A time of a few seconds can be set with
a capacitance under 0.1 µF.
Set time (seconds) ≈ 52 × C (µF)
To release the lock protection state, the IC must be set to the stopped state or the power must be turned off and
reapplied. The CROCK pin must be connected to ground if the lock protection circuit is not used.
10. Power supply stabilization
The large currents drawn by this IC can adversely affect the power supply voltage. Therefore a capacitor with a
sufficiently large value must be inserted between the VCC pin and ground. If a diode is inserted in the power supply
line to protect against destruction due to accidentally connecting the power supply with the polarity reversed, the
power supply line voltage will be even more easily affected and an even larger capacitor will be required.
No. 5687-7/11
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