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Fabricante

NJU7329A

Single-phase DC Brushless Motor Driver IC

Japan Radio Corporation  

NJU7329A

[Design Notes]

Above application example is designed for 5V operation with motor current of 350mA. It uses the following

components:

Hall Elements: HW101A (AKE)

1. Selection of C1 and D1:

C1 is used for a noise reduction purpose. A typical value is 0.1uF.

Optimize the value in actual operating conditions if necessary. D1 is a diode for protection against reverse voltage

supply. Silicon rectifier diode (WO3C, 10D1 and equivalent) is appropriate.

2. Lock Protection Function (Design of C2 value):

Lock Protection Function, consists of Motor Lock Detection and Auto Resume Function, is a safety feature to protect

a motor and a driver circuit from fatal destruction in case of motor halt.

Motor Lock Detection detects motor halt due to irregular load conditions and then cuts motor driving current f or

safety operation. A value of C2 determines Lock detection time (Ton) and Auto Resume Time (Toff).

Lock detection time (Ton) is given by:

[ ] TON

= C 2 VCL − VID

ICHG

sec

Where C2 is 0.47uF:

TON

=

0.47

×

10

−6

×

2.6 − 0.6

1.5 × 10 − 6

= 0.62[sec]

Auto Resume Time (Toff) is given by:

[ ] TOFF

= C 2 VCL − VID

IDCHG

sec

Where C2 is 0.47uF:

TOFF

=

0.47

×10

−

6

×

2.6 − 0.6

0.5 ×10−6

= 1.88[sec]

In actual application, Lock detection time (Ton) is affected by the mechanical time constant of a motor. Therefore,

constant start up must be confirmed in actual evaluation taking operating variations (i.e.Temperature, Voltage change

and so on) in consideration.

Ver.2003-07-28

-7 -

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