AN8787 Просмотр технического описания (PDF) - Panasonic Corporation

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производитель

AN8787

4-channel linear driver IC for CD/CD-ROM drive

Panasonic Corporation 

ICs for Compact Disc/CD-ROM Player

AN8787NSB

s Application Circuit Example (continued)

3. Load current IP3 flowing into load RL3 is supplied through pin 13 via the resistor RS3.

IP3

=

|

V14 −V12

RL3

|

4. Load current IP4 flowing into load RL4 is supplied through pin 9 via the resistor RS4.

IP4 =

| V10 −V8 |

RL4

5. Dissipation increase (∆PD) inside the IC (power output stage) caused by loads RL1, RL2, RL3 and RL4 is as follows:

∆PD = (VCC1 − | V20 −V18 |) ×

| V20 −V18 |

RL1

+

{VCC3

−

(RS3

+

RL3)

×

|

V14 −V12

RL3

|}

×

| V14 −V12 |

RL3

+ (VCC2 − | V17 −V15 |) ×

| V17 −V15 |

RL2

+

{VCC3

−

(RS4

+

RL4)

×

|

V10 −V8

RL4

|

}

×

| V10 −V8 |

RL4

6. Dissipation increase (∆PS) inside the IC (signal block supplied from pin 27) caused by loads RL1, RL2, RL3 and RL4

comes roughly as follows:

∆PS

=

3

×

V1

R1

×

(2

×

SVCC

+

|

V20

−V18

|

)

+

IP2

K

× (SVCC − | V17 −V15 | )

+

IP3

K

× (SVCC − | V14 −V12 | ) +

IP4

K

× (SVCC − | V10 −V8 | ), where K ≈ 100

7. Dissipation increase in a driver operating mode is ∆PD + ∆PS .

8. Allowable power dissipation without load (PD1) can be found as follows:

PD1 = SVCC × I(SVCC) +VCC1 × I(VCC1) + VCC2 × I(VCC2) +VCC3 × I(VCC3)

9. Allowable power dissipation in a load operating mode (PD) comes roughly as follows:

PD = PD1 + ∆PD + ∆PS

7

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