TS4997 datasheet(24/34 Pages) STMICROELECTRONICS

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Application information

TS4997

24/34

and the maximum value is obtained when:

and its value is:

Equation 5

Note:

This maximum value is only dependent on the power supply voltage and load values.

The efficiency is the ratio between the output power and the power supply:

Equation 6

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

The TS4997 is stereo amplifier so it has two 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 1 = Power dissipation of left channel power amplifier

●

Pdiss 2 = Power dissipation of right channel power amplifier

●

Total Pdiss =Pdiss 1 + Pdiss 2 (W)

In most cases, Pdiss 1 = Pdiss 2, giving:

The maximum die temperature allowable for the TS4997 is 150°C. In case of overheating, a

thermal shutdown protection set to 150°C, puts the TS4997 in standby until the temperature

of the die is reduced by about 5°C.

To calculate the maximum ambient temperature Tamb allowable, you need to know:

●

the power supply voltage value, VCC

●

the load resistor value, RL

●

the package type, RTHJA

Example: VCC=5V, RL=8Ω, RTHJAQFN16=85°C/W (with 2-layer PCB with vias).

Using the power dissipation formula given in Equation 5, the maximum dissipated power per

channel is:

Pdissmax = 633mW

And the power dissipated by both channels is:

Total Pdissmax = 2 x Pdissmax = 1266mW

∂Pdiss

∂P

out

--------------------- = 0

)

(

Vcc

max

Pdiss

η=

out

supply

------------------- =

πV

peak

4Vcc

--------------------

η= π

----- = 78.5%

TotalP

diss = 2

diss1

42V

π R

---------------------- P

out 2Pout W

()

–

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