Package characteristics
STM32F103xx
6.1
Thermal characteristics
The average chip-junction temperature, TJ, in degrees Celsius, may be calculated using the
following equation:
TJ = TA + (PD x ΘJA)
(1)
Where:
● TA is the Ambient Temperature in ° C,
● ΘJA is the Package Junction-to-Ambient Thermal Resistance, in ° C/W,
● PD is the sum of PINT and PI/O (PD = PINT + PI/O),
● PINT is the product of IDD and VDD, expressed in Watts. This is the Chip Internal Power.
PI/O represents the Power Dissipation on Input and Output Pins;
Most of the time for the application PI/O< PINT and can be neglected. On the other hand, PI/O
may be significant if the device is configured to drive continuously external modules and/or
memories.
An approximate relationship between PD and TJ (if PI/O is neglected) is given by:
PD = K / (TJ + 273 °C)
(2)
Therefore (solving equations 1 and 2):
K = PD x (TA + 273°C) + ΘJA x PD2
(3)
where:
K is a constant for the particular part, which may be determined from equation (3) by
measuring PD (at equilibrium) for a known TA. Using this value of K, the values of PD and TJ
may be obtained by solving equations (1) and (2) iteratively for any value of TA.
Table 46. Thermal characteristics
Symbol
Parameter
Thermal resistance junction-ambient
LFBGA100 - 10 x 10 mm / 0.5 mm pitch
Thermal resistance junction-ambient
LQFP100 - 14 x 14 mm / 0.5 mm pitch
ΘJA
Thermal Resistance Junction-Ambient
LQFP64 - 10 x 10 mm / 0.5 mm pitch
Thermal resistance junction-ambient
LQFP48 - 7 x 7 mm / 0.5 mm pitch
Value
41
46
45
55
Unit
°C/W
64/67