FAN8725 Ver la hoja de datos (PDF) - Fairchild Semiconductor

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FAN8725

Spindle Motor and 5-Channel Motor Driver

Fairchild Semiconductor 

Application Information

1. TORQUE CONTROL & OUTPUT CURRENT CONTROL

FAN8725 (KA3025)

Torque AMP

Ecr +

-

Ec

VM

+

VAMP

-

ECR-EC

Current Sense AMP

-

+

TSD

Gain

Controller

VM

+

Vcs

Rcs

-

Io

Driver

M

1) By amplifying the voltage difference between Ec and Ecr from Servo IC, the Torque Sense AMP produces the input volt-

age(VAMP) for the Current Sense AMP.

2) The output current (IO) is converted into the voltage (VCS) through the sense resistor (RCS) and compared with the VAMP.

By the negative feedback loop, the sensed output voltage, VCS is equal to the input VAMP. The output current (IO) is lin-

early controlled by the input VAMP.

3) The signals, EC and ECR can control the velocity of the Motor by controlling the output current (IO) of the Driver.

4) The range of the torque voltage is as shown below.

Current

[mA]

700

Reverse

Forward

Ecoff- Ecoff+

ECR > Ec

ECR < Ec

6

-1.0 V -50mV 0

50mV

1.0 V

ECR -EC

The input range of ECR, EC is 0.2 V ~ 4.0 V ( RCS = 0.5[Ω] )

Rotation

Forward rotation

Stop after detecting re-

verse rotation

11

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