TDA5345HT 데이터 시트보기 (PDF) - Philips Electronics

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TDA5345HT

5 V spindle & VCM driver combo

Philips Electronics 

Philips Semiconductors

5 V spindle & VCM driver combo

Preliminary specification

TDA5345HT

Act+

IVCM VCM

+ <=>

IVCM

VVCM

Act+

RVCM

LVCM

Act-

Fig.13 VCM motor model

VCM

back-EMF

e

+

Act-

VVCM=

(RVCM

× IVCM)

+





LV

C

M

×

-d---I--dV----Ct---M-- 

+

e

(8)

If the VCM current IVCM can be considered as constant, the back-EMF becomes:

e= VVCM – (RVCM × IVCM)

(9)

Figure 14 presents the VCM back-EMF amplifier as it is implemented in the TDA5345HT:

VcmMinus

(ext.)

Rsense

R2

(6)

(ext.) (30)

OpAmpInM

R1

(ext.)

IVCM

(ext.)

(22)

VcmSenseInM

VCM

VcmPlus

(11)

Fig.14 VCM back-EMF amplifier

OpAmpOut

(31)

R

2R

R = 10 kΩ

VcmBemf

R

(29)

2R

(18) VcmRef=1.482V

The first operational amplifier output voltage (OpAmpOut) is:

OpAmpOut=

V

c

m

S

e

n

s

e

I

n

M

–

RR-----12--

×

RS

ens

e

×

IVC



M

(10)

The VCM back-EMF amplifier output voltage (VcmBemf) is:

VcmBemf= 2 × (VcmPlus – OpAmpOut) + VcmRef

(11)

VcmBemf= 2 ×

V

c

m

P

l

u

s

–





V

c

m

S

e

n

s

e

I

n

M

–

〈

RR-----12--

×

RS

en

s

e

×

IV

C

M〉





+ VcmRef

(12)

1999 June 10

21

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