TDA8931
Philips Semiconductors
Power comparator 1 × 20 W
14.4.1 Thermal layout including vias
The bottom side of the double-sided PCB is used to place the SMD components including
the TDA8931T and the majority of the signal tracks. The topside is used to place the
leaded components.
The remaining area on both top and bottom layer are filled with ground plane for a proper
cooling. In this way it is possible to have a cooling area available of about:
• 40 % of the PCB area on the bottom (60 % for signal tracks and SMD components)
• 90 % of the PCB area on the top (10 % for signal tracks)
The PCB area required for a typical mono amplifier is 21.5 cm2 resulting in a cooling area
of about 28 cm2. Thermal vias should be placed close to corner leads for a proper heat
flow to the top layer of the PCB. Figure 7 is showing the thermal vias indicated as black
dots and Figure 8 is showing the heat flow to the copper area on the top layer.
20
1
top layer
bottom layer
TDA8931T
001aac239
10
11
001aac238
Fig 7. Thermal vias (top view)
Fig 8. Heat flow (cross section view)
14.4.2 Thermal considerations
To estimate the maximum junction temperature, the following equation can be used:
T j(max) = Tamb + Rth( j – a) × Pd
(5)
Where:
Tamb = ambient temperature
Pd = power dissipation in the TDA8931T
Rth(j-a) = thermal resistance from junction to ambient (24 K/W)
9397 750 13847
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
Preliminary data sheet
Rev. 01 — 14 January 2004
19 of 31
NXP [ NXP ]
