Datasheet

Package information STM32L475xx
198/204 DS10969 Rev 5
7.3 Thermal characteristics
The maximum chip junction temperature (T
J
max) must never exceed the values given in
Table 22: General operating conditions.
The maximum chip-junction temperature, T
J
max, in degrees Celsius, may be calculated
using the following equation:
T
J
max = T
A
max + (P
D
max x 
JA
)
Where:
• T
A
max is the maximum ambient temperature in °C,
• 
JA
is the package junction-to-ambient thermal resistance, in °C/W,
• P
D
max is the sum of P
INT
max and P
I/O
max (P
D
max = P
INT
max + P
I/O
max),
• P
INT
max is the product of all I
DDXXX
and V
DDXXX
, expressed in Watts. This is the
maximum chip internal power.
P
I/O
max represents the maximum power dissipation on output pins where:
P
I/O
max =  (V
OL
× I
OL
) +  ((V
DDIOx
– V
OH
) × I
OH
),
taking into account the actual V
OL
/ I
OL
and V
OH
/ I
OH
of the I/Os at low and high level in the
application.
7.3.1 Reference document
JESD51-2 Integrated Circuits Thermal Test Method Environment Conditions - Natural
Convection (Still Air). Available from www.jedec.org
7.3.2 Selecting the product temperature range
When ordering the microcontroller, the temperature range is specified in the ordering
information scheme shown in
Section 8: Ordering information.
Each temperature range suffix corresponds to a specific guaranteed ambient temperature at
maximum dissipation and, to a specific maximum junction temperature.
As applications do not commonly use the STM32L475xx at maximum dissipation, it is useful
to calculate the exact power consumption and junction temperature to determine which
temperature range will be best suited to the application.
The following examples show how to calculate the temperature range needed for a given
application.
Table 103. Package thermal characteristics
Symbol Parameter Value Unit

JA
Thermal resistance junction-ambient
LQFP64 - 10 × 10 mm / 0.5 mm pitch
45
°C/W
Thermal resistance junction-ambient
LQFP100 - 14 × 14mm
42
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