20 of 44 November 28, 2011
IDT 89HPES48H12G2 Data Sheet
Thermal Considerations
This section describes thermal considerations for the PES48H12G2 (27mm
2
FCBGA676 package). The data in Table 17 below contains informa-
tion that is relevant to the thermal performance of the PES48H12G2 switch.
Note: It is important for the reliability of this device in any user environment that the junction temperature not exceed the T
J(max)
value
specified in Table 17. Consequently, the effective junction to ambient thermal resistance (
θ
JA
) for the worst case scenario must be
maintained below the value determined by the formula:
θ
JA
= (T
J(max)
- T
A(max)
)/P
Given that the values of T
J(max)
, T
A(max)
, and P are known, the value of desired θ
JA
becomes a known entity to the system designer. How to
achieve the desired
θ
JA
is left up to the board or system designer, but in general, it can be achieved by adding the effects of θ
JC
(value
provided in Table 17), thermal resistance of the chosen adhesive (
θ
CS
), that of the heat sink (θ
SA
), amount of airflow, and properties of the
circuit board (number of layers and size of the board). It is strongly recommended that users perform their own thermal analysis for their own
board and system design scenarios.
Symbol Parameter Value Units Conditions
T
J(max)
Junction Temperature 125
o
C Maximum
T
A(max)
Ambient Temperature 70
o
C Maximum for commercial-rated products
85
o
C Maximum for industrial-rated products
θ
JA(effective)
Effective Thermal Resistance, Junction-to-Ambient
14.6
o
C/W Zero air flow
7.8
o
C/W 1 m/S air flow
6.4
o
C/W 2 m/S air flow
θ
JB
Thermal Resistance, Junction-to-Board 2.7
o
C/W
θ
JC
Thermal Resistance, Junction-to-Case 0.15
o
C/W
P Power Dissipation of the Device 12.44 Watts Maximum
Table 17 Thermal Specifications for PES48H12G2, 27x27 mm FCBGA676 Package
