TS4975 Datasheet, PDF (22/33 Pages) STMicroelectronics – Stereo Headphone Drive Amplifier with Digital Volume Control via IC Bus

Application Information
4.2 Power dissipation and efficiency
Hypotheses:
● Voltage and current in the load are sinusoidal (Vout and Iout).
● Supply voltage is a pure DC source (Vcc).
Regarding the load we have:
V_OUT = V_PEAK sin ωt(V)
and
I_OUT = ^V----R-O----^UL---^T--(A)
and
P_OUT = ^V----2-P2---R^E----^AL---^K--(A)
Single-ended configuration:
The average current delivered by the supply voltage is:
π
∫ IccAVG = 2--1--π-- -V----P-R--E--L--A---K-- sin (t)dt = V----π-P---RE----AL---K--(A)
0
Figure 59. Current delivered by supply voltage in single-ended model
TS4975
The power delivered by supply voltage is:
P_supply = V_CCI_CCAVG(W)
So, the power dissipation by each 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_{d i s s}
∂P_OUT
=
0
22/33