mpc5200cvr400br2 Freescale Semiconductor, Inc, mpc5200cvr400br2 Datasheet - Page 12

• Manufacturer Part Number: mpc5200cvr400br2
• Description: Mpc5200b 32-bit Embedded Processor
• Manufacturer: Freescale Semiconductor, Inc

Electrical and Thermal Characteristics
Historically, the thermal resistance has frequently been expressed as the sum of a junction to case thermal
resistance and a case to ambient thermal resistance:
where:
R
change the case to ambient thermal resistance, R
the device, add a heat sink, change the mounting arrangement on printed circuit board, or change the
thermal dissipation on the printed circuit board surrounding the device. This description is most useful for
ceramic packages with heat sinks where some 90% of the heat flow is through the case to the heat sink to
ambient. For most packages, a better model is required.
A more accurate thermal model can be constructed from the junction to board thermal resistance and the
junction to case thermal resistance. The junction to case covers the situation where a heat sink will be used
or where a substantial amount of heat is dissipated from the top of the package. The junction to board
thermal resistance describes the thermal performance when most of the heat is conducted to the printed
circuit board. This model can be used for either hand estimations or for a computational fluid dynamics
(CFD) thermal model.
To determine the junction temperature of the device in the application after prototypes are available, the
Thermal Characterization Parameter (Ψ
measurement of the temperature at the top center of the package case using the following equation:
where:
The thermal characterization parameter is measured per JESD51-2 specification using a 40-gauge type T
thermocouple epoxied to the top center of the package case. The thermocouple should be positioned, so
that the thermocouple junction rests on the package. A small amount of epoxy is placed over the
thermocouple junction and over approximately one mm of wire extending from the junction. The
thermocouple wire is placed flat against the package case to avoid measurement errors caused by cooling
effects of the thermocouple wire.
3.2
The MPC5200B System requires a system-level clock input SYS_XTAL. This clock input may be driven
directly from an external oscillator or with a crystal using the internal oscillator.
There is a separate oscillator for the independent Real-Time Clock (RTC) system.
12
θJC
is device related and cannot be influenced by the user. The user controls the thermal environment to
R
R
R
T
Ψ
P
D
T
θJA
θJC
θCA
JT
Oscillator and PLL Electrical Characteristics
= thermocouple temperature on top of package (ºC)
= power dissipation in package (W)
= thermal characterization parameter (ºC/W)
= junction to case thermal resistance (ºC/W)
= junction to ambient thermal resistance (ºC/W)
= case to ambient thermal resistance (ºC/W)
MPC5200B Data Sheet, Rev. 1
T
R
JT
J
θ
) can be used to determine the junction temperature with a
JA
= T
= R
T
+(
θCA
θ
Ψ
JC
JT
. For instance, the user can change the air flow around
+R
×
θ
P
CA
D
)
Freescale Semiconductor
Eqn. 4
Eqn. 5