CS35L00_11 Datasheet, PDF (32/34 Pages) Cirrus Logic – 2.8 W Mono Class-D Audio Amplifier with Low Idle Current

8.4.1
CS35L00
Determining Maximum Ambient Temperature
To determine (to a first order approximation) the maximum ambient temperature in which the CS35L00
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 “Characteristics & Specifications” section on
page 8.
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 “Characteristics & Specifications” section on page 8 can be
used. However, this method will predict higher operating temperatures than what may be seen in the ap-
plication, since power content of audio signals is much smaller than that of the sine wave used to establish
the power specifications.)
η = The efficiency of the device at the power P_max. (A safe, conservative assumption is 85%)
32
DS906PP1