NJM2640

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♦NJM2640 application note

The NJM2640 is a two-phase motor unipolar pre-driver IC featuring 60V operating high voltage process

technology.

It is suitable for fan motor drivers for communication equipment where 48V operation is required.

[Application Circuit Example]

[Design Notes]

Above application example is designed for 48V operation with motor current of 300mA. It uses the following

components:

Hall Elements: HW101A (AKD)

TR1,TR2: 2SD0968A (NEC)

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. When Lock Detection is activated; Lock Alert Out (LA: Pin 3) goes to L.

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

H1

H2

VCC

Ct

GND

OUT2

OUT1

LA

Motor

Hall

element

C2

R1

R3

R2

Ra

Lock alarm out

NJM2640

V+

GND

R4

R5

R4

R5

ZD1

ZD1

C1

D1

TR1

TR2

ZD2

ZD2

Ca

D2