7. PWM frequency

PWM frequency is determined from the capacity C (F) of capacitor connected to the PWM pin.

fPWM

.

=. 1/(14400

× C)

It is recommended to keep the PWM frequency at 15 – 25 kHz. GND of a capacitor to be connected must be connected

to the GND1 pin with the shortest possible wiring.

8. Hall input signal

The Hall input requires the signal input with an amplitude exceeding the hysteresis width (42 mV max). Considering

the effect of noise, the input with the amplitude of 100 mV or more is recommended.

When the output waveform is disturbed due to noise effects at a time of changeover of the output phase, connect a

capacitor between Hall input pins (+ and –) at a point as near as possible to the pin.

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

(because the motor current returns instantaneously to the power supply). When this problem exists, increase the

• 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 (3.5 A).

(F/R changeover at high rotation 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 10 µF (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

GND for stabilization. GND of a capacitor to be connected must be connected to the GND2 pin (GND of the power

block) at a point as near as possible to the pin. If a capacitor (electrolytic) cannot be provided near the pin because of

existence of a heat sink, etc., provide a ceramic capacitor of about 0.1 µF near the pin.

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. VREG stabilization

The VREG pin (5 V regulator output) that is a power supply for control circuit must be provided with a stabilizing

capacitor (about 0.1 µF). GND of a capacitor to be connected must be connected to the GND1 pin with the shortest

possible wiring.

13. 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.

No. 7099-10/12

LB1929