PdissMAX=V2CCπ2RL(W)

(9)

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= POUT

Psupply=πVpeak2VCC

(10)

The maximum theoretical value is reached when Vpeak = VCC/2, so

η=π4=78.5%

(11)

5.2

Total power dissipation

The TS488 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:

•

Pdiss R = power dissipation due to the right channel power amplifier

•

Pdiss L = power dissipation due to the left channel power amplifier

•

Total Pdiss = Pdiss R + Pdiss L (W)

Typically, Pdiss R is equal to Pdiss L, giving:

TotalPdiss=2PdissR=2PdissL

TotalPdiss=2 2VCCπRL POUT−2POUT

(12)

5.3

Lower cut-off frequency

The lower cut-off frequency FCL of the amplifier depends on input capacitors Cin and output capacitors Cout.

The input capacitor Cin (output capacitor Cout) in serial with the input resistor Rin (load resistor RL) of the amplifier

is equivalent to a first order high pass filter. Assuming that FCL is the lowest frequency to be amplified (with a 3 dB

attenuation), the minimum value of the Cin (Cout) is:

Cin= 1

2π⋅FCL⋅Rin

Cout= 1

2π⋅FCL⋅RL

(13)

Figure 75. Lower cut-off frequency vs. input capacitor

1

10

100

1000

10

100

1k

10k

Rin=50kΩ

Rin=100k Ω

Rin=20k Ω

Cin (nF)

Rin=10kΩ

Figure 76. Lower cut-off frequency vs. output capacitor

0.1

1

10

100

1000

10

100

1k

10k

R

L=32Ω

R

L=600Ω

R

L=16Ω

Cout (μF)

TS488

Total power dissipation

DS4579 - Rev 8

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