FBFM2112F897CSLJLS View Datasheet(PDF) - Intel

Part Name

Description

Manufacturer

FBFM2112F897CSLJLS

Intel® FM2112 24-Port 10G/1G Ethernet Switch Chip

Intel 

Intel® FM2112 24-Port 10G/1G Ethernet Switch Chip Data Sheet

Notes:

6.6.3

temperature of 125 ºC. With a junction-to-case thermal resistance

(θJC) of only 0.15 ºC/W, even the highest allowed value of case

temperature, 115ºC, will keep the junction temperature below 125ºC.

This is true even assuming a worst case power dissipation approaching

20W, which results in a 3ºC rise in junction temperature over case

temperature (20W x 0.15ºC/W = 3ºC).

The relevant thermal parameters for choosing or designing a heat sink

are listed in Table 193. A heat sink is chosen based on the value of CA it

gives in the presence of the anticipated airflow. The resulting case

temperature is calculated using the parallel combination of θCA and

ΨJB multiplied by the expected power dissipation.

Table 193. FM2112 Thermal Parameters

Parameter

θJC

ΨJB1,2

Pdiss(max)

TCASE(max)

Description

Value

Thermal resistance, junction to case

Thermal resistance, junction to board

Maximum power dissipation. 8 ports operating in 10G

mode and 16 ports operating in 1G mode. Min frame size

(64B) and min IFG (12B) on all ports.

Maximum case

temperature

Commercial, -C

Extended, -E

Industrial, -I

0.15 ºC/Watt

4.5 ºC/Watt

19 Watts

85 ºC

105 ºC

115 ºC

(1) This parameter is similar to JB as defined by JEDEC, except that the presence of an

isothermal cold ring is not assumed. The value of JB is more relevant to real world use

scenarios.

(2) The PC board is assumed to be at ambient temperature.

Temperature Sensor Operation

The FM2112 has an integrated temperature sensing diode on board

with LVTTL outputs DIODE_IN and DIODE_OUT. Die temperature is

read using these outputs through a temperature sensor IC such as the

National LM95231. The temperature as reported by this IC has been

checked in temperature controlled conditions across a range of

temperatures. It was found that the LM95231 measured temperature

was higher than the controlled case temperature by approximately 11

to 13 °C. Table 194 shows the corrections that must be applied to the

LM95231 temperature to arrive at the correct case temperature.

Temperature readings with thisIC are not expected to be degree-

accurate, but approximately +/- 5°C. Temperature accuracy with other

IC's is unspecified and may vary significantly from the table below,

especially for those IC's where series resistance nulling is used.

161

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