No. 7110-10/11

LB11827

4. Power save circuit

This IC enters the power save condition to decrease the current dissipation in the stop mode. In this condition, the bias

current of most of circuits is cut off. Even in the power save condition, the 5 V regulator output is given.

5. Reference clock

This is entered from the external signal source (1 MHz max) via a resistor (reference: about 5.1 k

Ω) in series with the

XI pin. The XO pin is left open.

Input signal source levels:

Low-level voltage: 0 to 0.8 V

High-level voltage: 2.5 to 5.0 V

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.

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 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