1997 Jul 10

13

Philips Semiconductors

Product specification

Brushless DC motor and VCM drive circuit

with speed control

TDA5341

The power for retraction is received from the rectification

of the EMF of the spindle before it is spun down.

After retraction, a brake procedure is automatically settled.

The time needed for retraction, prior to braking, can be

precisely adjusted with the external RC device connected

to pin BRAKEDELAY. The discharge of the capacitance

provide the desired time constant.

Actuator section

The actuator driver has a control input voltage that is

proportional to the actuator current which is capable of a

closed-loop band-pass frequency higher than 10 kHz.

An operational amplifier input allows passive external

components for compensation and gain setting.

The compensation amplifier is able to be pulled out of a

saturation state within 5

µs and its output swing is

An actuator current-sense amplifier is provided for use by

the disc drive controller. The gain from current-sense

resistor to sense the amplifier output is typically 10 (

±3%)

and the output voltage swing is

±1.25 V. An input common

mode range insures operation through all normal coil

voltage excursions. Maximum recovery time from

saturation is 20

µs (typ.).

With GAINSEL = LOW;

Fig.6 VCM section application diagram.

handbook, full pagewidth

VCMIN2

RIN1

CL2

CL1

RIN2

Rf

VCMIN1

Vref

GAINSEL

input

FB2

FB1

actuator

VCM

−

SENSEIN

−

VCM

+

SENSEIN

+

SENSEOUT

PREAMP

SENSE

AMP

OUTPUT

GAIN 11

TDA5341

MGE825

Rs

T11

R

f

×

Z

L

×

1

R

IN

R

f

R

s

R

f

Z

VCM

110

R

s

×

Z

L

×

+

×

+

×

()

×

--------------------------------------------------------------------------------------------------------------------





×

–

=

R

IN

R

IN1

R

IN2

×

R

IN1

R

IN2

+

------------------------------

=