AN8787NSB Datasheet, PDF (7/7 Pages) Panasonic Semiconductor – 4-channel linear driver IC for CD/CD-ROM drive

ICs for Compact Disc/CD-ROM Player
AN8787NSB
s Application Circuit Example (continued)
3. Load current I_P3 flowing into load RL3 is supplied through pin 13 via the resistor RS3.
I_P3
=
|
V₁₄ −V₁₂
R_L3
|
4. Load current I_P4 flowing into load RL4 is supplied through pin 9 via the resistor RS4.
I_P4 =
| V₁₀ −V₈ |
R_L4
5. Dissipation increase (∆P_D) inside the IC (power output stage) caused by loads RL1, RL2, RL3 and RL4 is as follows:
∆P_D = (V_CC1 − | V₂₀ −V₁₈ |) ×
| V₂₀ −V₁₈ |
R_L1
+
{V_CC3
−
(R_S3
+
R_L3)
×
|
V₁₄ −V₁₂
R_L3
|_}
×
| V₁₄ −V₁₂ |
R_L3
+ (V_CC2 − | V₁₇ −V₁₅ |) ×
| V₁₇ −V₁₅ |
R_L2
+
{V_CC3
−
(R_S4
+
R_L4)
×
|
V₁₀ −V₈
R_L4
|
}
×
| V₁₀ −V₈ |
R_L4
6. Dissipation increase (∆P_S) inside the IC (signal block supplied from pin 27) caused by loads RL1, RL2, RL3 and RL4
comes roughly as follows:
∆P_S
=
3
×
V₁
R₁
×
(2
×
SV_CC
+
|
V₂₀
−V₁₈
|
)
+
I_P2
K
× (SV_CC − | V₁₇ −V₁₅ | )
+
I_P3
K
× (SV_CC − | V₁₄ −V₁₂ | ) +
I_P4
K
× (SV_CC − | V₁₀ −V₈ | ), where K ≈ 100
7. Dissipation increase in a driver operating mode is ∆P_D + ∆P_S .
8. Allowable power dissipation without load (P_D1) can be found as follows:
P_D1 = SV_CC × I_(SVCC) +V_CC1 × I_(VCC1) + V_CC2 × I_(VCC2) +V_CC3 × I_(VCC3)
9. Allowable power dissipation in a load operating mode (P_D) comes roughly as follows:
P_D = P_D1 + ∆P_D + ∆P_S
7