CS35L01 Datasheet, PDF (32/34 Pages) Cirrus Logic – 2.9 W Mono Class-D Audio Amplifier with Low Idle Current

8.3.1
CS35L01/03
Determining Maximum Ambient Temperature
To determine (to a first order approximation) the maximum ambient temperature in which the CS35L01/03
will operate, the following equations can be used:
T_op = θ_JA × ((1 – η) × P_max)
T_max = T_TE – T_op
Where:
T_max = The maximum ambient temperature in which the device can operate.
T_op = The operating temperature of the device, given a dissipated power “P_max” and a known thermal
impedance “θ_JA”.
T_TE = The Over-Temperature Error Threshold, given in the “Electrical Characteristics - All Operational
Modes” section on page 9.
θ_JA = The thermal impedance of the device and PCB. (This value is highly subjective to a number of ap-
plication specific scenarios. The numbers given in Table 2 on page 31 can be used for a first order ap-
proximation, but proper characterization of the application’s specific PCB and supporting mechanicals is
needed to increase the accuracy of the result achieved here.)
P_max = The maximum power at which the amplifier will be operated continuously. (For conservative esti-
mates, the 10% THD+N rated power given in “Electrical Characteristics - SD Mode” section on page 10,
“Electrical Characteristics - FSD Mode” section on page 11, “Electrical Characteristics - HD Mode” section
on page 12, or “Electrical Characteristics - FHD Mode” section on page 13 can be used. However, this
method will predict higher operating temperatures than what may be seen in the application, since power
content of audio signals is much smaller than that of the sine wave used to establish the power specifica-
tions.)
η = The efficiency of the device at the power P_max.
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