Datasheet

Thermal characteristics STM8S105x4/6
106/121 DocID14771 Rev 15
12 Thermal characteristics
The maximum junction temperature (T
Jmax
) of the device must never exceed the values
specified in
Table 18: General operating conditions, otherwise the functionality of the device
cannot be guaranteed.
The maximum junction temperature T
Jmax
, in degrees Celsius, may be calculated using the
following equation:
T
Jmax
= T
Amax
+ (P
Dmax
x 
JA
)
Where:
 T
Amax
is the maximum ambient temperature in C

JA
is the package junction-to-ambient thermal resistance in C/W
 P
Dmax
is the sum of P
INTmax
and P
I/Omax
(P
Dmax
= P
INTmax
+ P
I/Omax
)
 P
INTmax
is the product of I
DD
and V
DD
, expressed in Watts. This is the maximum chip
internal power.
 P
I/Omax
represents the maximum power dissipation on output pins
Where:
P
I/Omax
= (V
OL
*I
OL
) + ((V
DD
-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.
12.1 Reference document
JESD51-2 integrated circuits thermal test method environment conditions - natural
convection (still air). Available from www.jedec.org.
Table 56. Thermal characteristics
(1)
1. Thermal resistances are based on JEDEC JESD51-2 with 4-layer PCB in a natural convection
environment.
Symbol Parameter Value Unit

JA
Thermal resistance junction-ambient
LQFP48 - 7x7 mm
°C/W
Thermal resistance junction-ambient
LQFP44 - 10x10 mm
Thermal resistance junction-ambient
LQFP32 - 7x7 mm
Thermal resistance junction-ambient
UFQFPN32 - 5x5 mm
Thermal resistance junction-ambient
SDIP32 - 400 ml
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