TS488 Datasheet, PDF (22/32 Pages) STMicroelectronics – Pop-free 120mW stereo headphone amplifier

Application information
4
Application information
TS488-TS489
4.1
Power dissipation and efficiency
Hypotheses:
■ Voltage and current in the load are sinusoidal (V_out and I_out).
■ Supply voltage is a pure DC source (V_CC).
Regarding the load we have:
V_OUT = V_PEAK sin ωt(V)
and
I_OUT
=
V_{-----O----U---T--}
R_L
(
A
)
and
P_OUT
=
V_{-----P2---E----A---K--}
2R_L
(A)
The average current delivered by the power supply voltage is:
π
∫ ^ICC_AVG ⁼ ₂^--1--_π^--
V_{-----P---E----A---K--}
R_L
sin
(
t
)
dt
=
V_{-----P---E----A---K--}
πR_L
(
A
)
0
Figure 78. Current delivered by power supply voltage in single-ended configuration
Icc (t)
Vpeak/R_L
Icc_AVG
0
T/2
T
3T/2
2T Time
The power delivered by power supply voltage is:
P_supply = V_CCI_CCAVG(W)
So, the power dissipation by each power amplifier is
P_diss = P_supply–P_OUT(W)
P_diss
=
-----²---^V-----^C---^C--
π R_L
P_OUT – P_OUT(W)
and the maximum value is obtained when:
∂P_{diss = 0}
∂P_OUT
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