TS488 Datasheet, PDF (23/32 Pages) STMicroelectronics – Pop-free 120mW stereo headphone amplifier

TS488-TS489
Application information
and its value is:
P_dissMAX
=
--^V----^C2----^C--
π²R_L
(
W
)
Note: This maximum value depends only on power supply voltage and load values.
The efficiency is the ratio between the output power and the power supply:
η = ---^P----^O----^U----^T--- = -^π---^V----^p---^e---^a---^k-
P_supply 2V_CC
The maximum theoretical value is reached when V_peak = V_CC/2, so
η = -^π- = 78.5%
4
4.2
Total power dissipation
The TS488/9 is stereo (dual channel) amplifier. It has two independent power amplifiers.
Each amplifier produces heat due to its power dissipation. Therefore the maximum die
temperature is the sum of each amplifier’s maximum power dissipation. It is calculated as
follows:
■ P_{diss R} = Power dissipation due to the right channel power amplifier.
■ P_{diss L} = Power dissipation due to the left channel power amplifier.
■ Total P_diss = P_{diss R} + P_{diss L} (W)
Typically, P_{diss R} is equal to P_{diss L}, giving:
TotalP_diss = 2P_dissR = 2P_dissL
TotalP_diss
=
2_--------2_----V_----C----C--
π R_L
P_OUT – 2P_OUT
4.3
Lower cut-off frequency
The lower cut-off frequency F_CL of the amplifier depends on input capacitors C_in and output
capacitors C_out.
The input capacitor C_in (output capacitor C_out) in serial with the input resistor R_in (load
resistor R_L) of the amplifier is equivalent to a first order high pass filter. Assuming that F_CL is
the lowest frequency to be amplified (with a 3dB attenuation), the minimum value of the C_in
(C_out) is:
C_in = ₂----_π-----_â‹------_F----_C¹---_L----_â‹------_R-----_i-_n-
C_out
=
------------------¹--------------------
2π ⋅ F_CL ⋅ R_L
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