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LB1825

Three-Phase Brushless Motor Driver

SANYO -> Panasonic 

LB1825

4. Reference signal input circuit

• Internal clock mode (crystal oscillator)

The values of the external components associated with the crystal oscillator must be set up according to the

frequency of the oscillator. (See Table 1.) To avoid trouble with the oscillator circuit, confirm the component

values used with the oscillator’s manufacturer.

• External clock mode

Use the external circuit shown in Figure 2 to input the clock signal when controlling the motor speed using a

reference signal with the same frequency as FG.

5. Start/stop

When driving motors such as polygon mirror motors, the motor is normally stopped by turning off motor drive and

putting the motor in the free-running state. For this type of motor, set the S/B pin low and attach an external

transistor at FGOUT1 as shown in the Sample Application Circuit (Optical Disk Spindle Motor) figure to start and

stop the drive. (Motor drive is turned off when FGOUT1 is low.)

6. Start/brake

When driving motors such as optical disk spindle motors, stopping is performed by applying some form of braking.

In these applications it is necessary for the motor to decelerate briefly and come to a complete stop. See the Sample

Application Circuit (Optical Disk Spindle Motor) figure for a sample circuit for this case. (The difference between

this circuit and the circuit shown in the Sample Application Circuit (Optical Disk Spindle Motor) figure is the

addition of the capacitor C5 to the S/B pin start/brake circuit.)

Braking Operation

This braking circuit applies full torque reverse rotation braking (in the current limited state) directly after the S/B pin is

set low while the motor is turning. After that, the reverse torque is gradually decreased (according to the time constant

determined by R4 and C5) at the points where the speed falls below the values listed below. This operation brings the

disk to a full stop.

f3H = fFG/32 (FG mode)

f3H = fFG/8 (Triple Hall FG mode) f3H: Triple Hall input composite frequency.

f3H = fFG/2 (Single Hall FG mode) fFG: The FG frequency when locked

Depending on the size of the disk and the motor torque the following adjustments may be required to improve the disk

stopping characteristics.

1. Increase the time constant if the motor continues to rotate in the forward direction after the braking torque has gone

to zero.

2. Decrease the time constant if the motor is observed to rotate in the reverse direction due to the braking operation.

3. A value of about 51 kΩ is recommended for R4. In particular, it should be under 100 kΩ.

s No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace

equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of

which may directly or indirectly cause injury, death or property loss.

s Anyone purchasing any products described or contained herein for an above-mentioned use shall:

ΠAccept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and

distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all

damages, cost and expenses associated with such use:

 Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on

SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees

jointly or severally.

s Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for

volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied

regarding its use or any infringements of intellectual property rights or other rights of third parties.

This catalog provides information as of August, 1997. Specifications and information herein are subject to

change without notice.

No. 4845-9/9

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