TS4995 Datasheet, PDF (19/26 Pages) STMicroelectronics – 1.2 W fully differential audio power amplifier with selectable standby and 6 dB fixed gain

TS4995
Application information
Note:
Therefore, the power dissipated by each amplifier is:
P_diss = P_supply - P_out (W)
P_diss
=
2_--------2_----V_----C----C--
π R_L
P_out–P_out
and the maximum value is obtained when:
∂_----P_----d_----i_-s_----s_---
∂P_out
=
0
and its value is:
Equation 3
Pdiss max
=
2 Vcc²
π²R_L
(W)
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 4
η=
-----^P----^o---^u---^t---
P_supply
=
--^π----^V----^p---^e---^a---^k-
4V_CC
The maximum theoretical value is reached when V_peak = V_CC, so:
η= -^π--- = 78.5%
4
The maximum die temperature allowable for the TS4995 is 125° C. However, in case of
overheating, a thermal shutdown set to 150° C, puts the TS4995 in standby until the
temperature of the die is reduced by about 5° C.
To calculate the maximum ambient temperature T_amb allowable, you need to know:
● The power supply voltage, V_CC
● The load resistor value, R_L
● The package type, R_thja
Example: V_CC=5 V, R_L=8 Ω, R_{thja-flipchip}= 100° C/W (100 mm² copper heatsink).
Using the power dissipation formula given above in Equation 3, this gives a result of:
P_dissmax = 633mW
T_amb is calculated as follows:
Equation 5
T_amb= 125° C – R_thja × P_dissmax
Therefore, the maximum allowable value for T_amb is:
T_amb = 125-100x0.633=61.7° C
19/26