CS3511 Datasheet, PDF (23/26 Pages) Cirrus Logic – Stereo 10 W High-efficiency Class-D Audio Power Amplifier

9. THERMAL CHARACTERISTICS
Parameter
Junction to Case Thermal Impedance
CS3511
Symbol Min Typ Max Units
θ_JC
-
1
-
°C/Watt
9.1 Thermal Flag
This device is designed to have the metal flag on the bottom of the device soldered directly to a metal plane
on the PCB. To enhance the thermal dissipation capabilities of the system, this metal plane should be cou-
pled with vias to a large metal plane on the backside (and inner ground layer, if applicable) of the PCB.
In either case, it is beneficial to use copper fill in any unused regions inside the PCB layout, especially those
immediately surrounding the CS3511. In addition to improving in electrical performance, this practice also
aids in heat dissipation.
The heat dissipation capability required of the metal plane for a given output power can be calculated as
follows:
θ_CA = [(T_J(MAX) - T_A) / P_D] - θ_JC
where,
θ_CA = Thermal resistance of the metal plane in °C/Watt
T_J(MAX) = Maximum rated operating junction temperature in °C, equal to 150 °C
T_A = Ambient temperature in °C
P_D = RMS power dissipation of the device, equal to 0.176*P_RMS-OUT (assuming 85% efficiency)
θ_JC = Junction-to-case thermal resistance of the device in °C/Watt, equal to 1 °C/Watt
DS845PP2
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