M54687FP Просмотр технического описания (PDF) - Renesas Electronics

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M54687FP

Bi-Directional Motor Driver with Governor

Renesas Electronics 

M54687FP

Speed Control Method

(1) Speed Control Method I (See the application circuit drawing.)

For PLAY/REV

Rotation number can be expressed by the following formula:

N=

1

Ka

{IB

•

RT+Vref (1+

RT )+la(

RT+RS

RT

K

-Ra)} •

•

•

•

•

•

(1)

Where:

Motor generation constant: Ka, Motor armature resistance: Ra, Rotation number: N

K: Current proportional constant, IB: PSC pin bias current,

Ia:motor current

RT, RS: External resistance

In addition, to set the rotation number with RS, external resistance RT is generally set as follows:

RT ≤ K × Ra

For FF/REW

Note that the rotation number is basically controlled with the same expression as formula (1) but different reference

voltage

Vref and different bias current IB are to be used.

However, Vref 5VR+0.5

(2) Speed Control Method II (to increase the motor rotation number)

RS

RT

RT

M

PSC1 O1

O2 PSC2

VR

VCC

R

L

S

L-G

P-G

Control signal

In the external circuit above, the voltage across motors is almost determined by the ratio of ‘RS+RT’ to ‘RT’ and,

therefore, a value set for the voltage across motors is not so large.

As method (1) of speed control I, the rotation number can be controlled.

However, the following relations must be satisfied:

RT→RT+RS

RS+RT→RT

Rev.1.0, Sep.19.2003, page 6 of 8

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