LB1695D 데이터 시트보기 (PDF) - SANYO -> Panasonic

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LB1695D

Three-Phase Brushless Motor Driver for DC Fan

SANYO -> Panasonic 

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LB1695D

Because the current limiter circuit is slanted towards the ON time for turning the sink-side output on again,

the reverse current will not be so large even if a rectifying diode (without a short reverse recovery time) is

used as regenerative current absorption diode connected externally.

7-3. Output off time setting

The output off time must be optimized for the type of motor that is being controlled. The output off time

setting is controlled by the external resistance connected to the R pin and the external capacitance connected

to the C pin. Figure 1 shows the current limiter operating waveform.

(1) Short output off time setting

Because the IC is designed internally to give a ratio of about 3:1 for the output off time and output

current ignore time, the two values cannot be set independently. If the output off time is set to a very

small value, the output current ignore time may be too short. In such a case, the external regenerative

current absorption diode acts to limit current flow by its reverse current (see section 7-2). If the output

off time is small, the diode reverse current will increase, which can lead to ASO problems.

(2) Long output off time setting

If the output off time is set to a very high value, the average current will be reduced, resulting in lower

motor startup torque. Depending on the motor type, the circuit may not change from the current limiter

operating state to the normal rotation state.

2.0V

t so

t sm

C pin voltage

0.4V

0.0V

0.5V

RF pin voltage

0.0V

t off

Figure. 1 Current limiter operating waveform

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No. 6205-9/10

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