16 of 50 December 16, 2013
IDT 89HPES24T3G2 Datasheet
Thermal Considerations — Option A Package
This section describes thermal considerations for the PES24T3G2 (19mm
2
FCBGA324 package). The data in Table 17 below contains information
that is relevant to the thermal performance of the PES24T3G2 switch.
Thermal Considerations — Option B Package
This section describes thermal considerations for the PES24T3G2 (27mm
2
FCBGA676 package). The data in Table 18 below contains information
that is relevant to the thermal performance of the PES24T3G2 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 (
JA
) for the worst case scenario must be
maintained below the value determined by the formula:
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
JA
becomes a known entity to the system designer. How to
achieve the desired
JA
is left up to the board or system designer, but in general, it can be achieved by adding the effects of
JC
(value
provided in Table 17), thermal resistance of the chosen adhesive (
CS
), that of the heat sink (
SA
), amount of airflow, and properties of the
circuit board (number of layers and size of the board). As a general guideline, this device will not need a heat sink if the board has 8 or more
layers AND the board size is larger than 4"x12" AND airflow in excess of 0.5 m/s is available. 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
CMaximum
T
A(max)
Ambient Temperature 70
o
CMaximum
JA(effective)
Effective Thermal Resistance, Junction-to-Ambient
16.8
o
C/W Zero air flow
10.1
o
C/W 1 m/S air flow
9.2
o
C/W 2 m/S air flow
JB
Thermal Resistance, Junction-to-Board 4.1
o
C/W
JC
Thermal Resistance, Junction-to-Case 0.3
o
C/W
P Power Dissipation of the Device 4.31 Watts Maximum
Table 17 Thermal Specifications for PES24T3G2, 19x19 mm FCBGA324 Package
Symbol Parameter Value Units Conditions
T
J(max)
Junction Temperature 125
o
CMaximum
T
A(max)
Ambient Temperature 70
o
CMaximum
JA(effective)
Effective Thermal Resistance, Junction-to-Ambient
14.6
o
C/W Zero air flow
8.2
o
C/W 1 m/S air flow
7.2
o
C/W 2 m/S air flow
JB
Thermal Resistance, Junction-to-Board 3.1
o
C/W
JC
Thermal Resistance, Junction-to-Case 0.3
o
C/W
P Power Dissipation of the Device 4.31 Watts Maximum
Table 18 Thermal Specifications for PES24T3G2, 27x27 mm FCBGA676 Package
