Cirrus Logic CS4970x4 - Manual (Page 10)

CS4970x4 Data Sheet
32-bit High Definition Audio Decoder DSP Family
DS752F1 10
5.5 Thermal Data (128-pin LQFP)
Notes: 1. Two-layer board is specified as a 76 mm X 114 mm, 1.6 mm thick FR-4 material with 1-oz. copper covering 20% of the top and
bottom layers.
2. Four-layer board is specified as a 76 mm X 114 mm, 1.6 mm thick FR-4 material with 1-oz. copper covering 20% of the top and
bottom layers and 0.5-oz. copper covering 90% of the internal power plane and ground plane layers.
3. To calculate the die temperature for a given power dissipation

j
= Ambient Temperature + [ (Power Dissipation in Watts) *

ja
]
4. To calculate the case temperature for a given power dissipation

c
=

j
- [ (Power Dissipation in Watts) *

jt
Parameter Symbol Min Typ Max Unit
Thermal Resistance (Junction to Ambient)
Two-layer Board
1
Four-layer Board
2

ja
—
— 53
44 —
—
°C / Watt
Thermal Resistance (Junction to Top of Package)
Two-layer Board 1
Four-layer Board
2

jt
—
— .45
.39 —
—
°C / Watt