Cirrus Logic CS35L00 - Manual (Page 31)

CS35L00
DS906PP1 31
8.2 Recommend PCB Footprint and Routing Configuration
To ensure high-yield manufacturability, the PCB footprint for the CS35L00 should be constructed with strict
adherence to the specifications given in IPC-610. Departure from this specification significantly increases
the probability of solder bridging and other manufacturing defects.
Routing of the traces into and out of the CS35L00 device should also be given consideration to avoid man-
ufacturing issues.
8.3 Package Thermal Performance
Class D amplifiers, though highly efficient, produce heat through the process of amplifying the audio signal.
As is well understood, the amount of heat is very small compared to that of traditional Class AB amplifiers.
Even so, as power levels increase and package sizes decrease, careful consideration must be given to en-
sure that thermal energy is removed from the device as efficiently as possible so that its operating temper-
ature is kept under its Over-Temperature Error Threshold.
The thermal impedance, θ
JA
is a measurement of the impedance to the flow of thermal energy out of the
device to the environment surrounding the device. This specification is directly related to the ability of the
PCB to which the CS35L00 is attached to transfer the heat from the device. The thermal impedance from
the junction of the device to the ambient surrounding the device and the thermal impedance from the device
into the PCB is shown in
Table 2 .
.
Table 2.
θ
JA
Specification for Typical PCB Designs
Note:
21. Test Printed Circuit Board Assembly (PCBA) constructed in accordance with JEDEC standard
JESD51-9. Two-signal, two-plane (2s2p) PCB used.
22. Test conducted with still air in accordance with JEDEC standards JESD51, JESD51-2A, and JESD51-
8.
8.4 DFN Thermal Pad
The CS35L00 is available in a compact DFN package. The underside of the DFN package reveals a large
metal pad that serves as a thermal relief to provide for maximum heat dissipation. This pad must mate with
an equally dimensioned copper pad on the PCB and must be electrically connected to PGND. A series of
thermal vias should be used to connect this copper pad to one or more larger ground planes on other PCB
layers; the copper in these ground planes will act as a heat sink for the CS35L00.
Parameter (Note 21) , (Note 22) Symbol Min Typical Max Units
Junction to Ambient Thermal Impedance θ
A
- 100 - °C/Watt
Junction to Printed Circuit Board Thermal Impedance θ
PCB
- 70 - °C/Watt