RTL8208B-LF/RTL8208BF-LF
Datasheet
9.7. Thermal Characteristics
Heat generated by the chip causes a temperature rise of the package. If the temperature of the chip (Tj,
junction temperature) is beyond the design limits, there will be negative effects on operation and the life
of the IC package. Heat dissipation, either through a heat sink or electrical fan, is necessary to provide a
reasonable environment (Ta, ambient temperature) in a closed case. As power density increases, thermal
management becomes more critical. A method to estimate the possible Ta is outlined below.
Thermal parameters are defined according to JEDEC standard JESD 51-2, 51-6:
θja (Thermal resistance from junction to ambient), represents resistance to heat flow from the chip to
ambient air. This is an index of heat dissipation capability. A lower θja means better thermal performance.
θja = (Tj - Ta) / Ph
Where Tj is the junction temperature
Ta is the ambient temperature
Ph is the power dissipation
θjc (Thermal resistance from junction to case), represents resistance to heat flow from the chip to the
package top case. θjc is important when an external heat sink is attached on the package top.
θjc = (Tj - Tc) / Ph, where Tj is the junction temperature
Figure 30. Cross-section of 128-Pin QFP
9.7.1. Thermal Operating Range
Table 47. Thermal Operating Range
Parameter
SYM Conditions
Min
Typical Max
Units
Junction operating
temperature
Tj
-
25
125
°C
Ambient operating
temperature
Ta
-
25
70
°C
9.7.2. Thermal Resistances
Table 48. Thermal Resistances
SYM Conditions
Parameter
Min
Typical Max
Units
Thermal resistance:
junction to ambient
Thermal resistance:
junction to case
2 layer PCB, 0 ft/s airflow
-
28.2
-
θja
°C/W
2 layer PCB, 0 ft/s airflow
-
2.0
-
θjc
°C/W
Note: PCB conditions (JEDEC JESD51-7)
Single-Chip Octal 10/100-TX/FX PHY Transceiver
57
Track ID: JATR-1076-21 Rev. 1.3
REALTEK [ Realtek Semiconductor Corp. ]
