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