Datasheet

STM8S105xx
Thermal characteristics
12 Thermal characteristics
The maximum chip junction temperature (T
Jmax
) must never exceed the values given in
Section 7.10: "TIM1 - 16-bit advanced control timer"
The maximum chip-junction temperature, T
Jmax
, in degrees Celsius, may be calculated
using the following equation:
T
Jmax
= T
Amax
+ (P
Dmax
x Θ
JA
)
Where:
• T
Amax
is the maximum ambient temperature in °C
• Θ
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
andV
DD
, expressed in Watts. This is the maximum chip
internal power.
• P
I/Omax
represents the maximum power dissipation on output pinsWhere:P
I/Omax
=Σ
(V
OL
*I
OL
) + Σ((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.
Table 57: Thermal characteristics (1)
Symbol Parameter Value Unit
Θ
JA
Thermal resistance junction-ambient
LQFP 48 - 7 x 7 mm
57 °C/W
Θ
JA
Thermal resistance junction-ambient
LQFP 44 - 10 x 10 mm
54 °C/W
Θ
JA
Thermal resistance junction-ambient
LQFP 32 - 7 x 7 mm
60 °C/W
Θ
JA
Thermal resistance junction-ambient
UFQFPN 32 - 5 x 5 mm
38 °C/W
Θ
JA
Thermal resistance junction-ambient
SDIP 32 - 400 mils
60 °C/W
1. Thermal resistances are based on JEDEC JESD51-2 with 4-layer PCB in a natural
convection environment.
12.1 Reference document
JESD51-2 integrated circuits thermal test method environment conditions - natural
convection (still air). Available from www.jedec.org.
12.2 Selecting the product temperature range
When ordering the microcontroller, the temperature range is specified in the order code.
The following example shows how to calculate the temperature range needed for a given
application.
Assuming the following application conditions:
• Maximum ambient temperature T
Amax
= 82 °C (measured according to JESD51-2)
• I
DDmax
= 15 mA, V
DD
= 5.5 V
DocID14771 Rev 13 87/99