Datasheet

Reference document12.1
JESD51-2 integrated circuits thermal test method environment conditions - natural convection
(still air). Available from www.jedec.org.
Selecting the product temperature range12.2
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
•
Maximum 8 standard I/Os used at the same time in output at low level with I
OL
= 10 mA,
V
OL
= 2 V
•
Maximum 4 high sink I/Os used at the same time in output at low level with I
OL
= 20 mA,
V
OL
= 1.5 V
•
Maximum 2 true open drain I/Os used at the same time in output at low level with I
OL
=
20 mA, V
OL
= 2 V
P
INTmax
= 15 mA x 5.5 V = 82.5 mW
P
IOmax
= (10 mA x 2 V x 8 )+(20 mA x 2 V x 2)+(20 mA x 1.5 V x 4) = 360 mW
This gives: P
INTmax
= 82.5 mW and P
IOmax
360 mW:
P
Dmax
= 82.5 mW + 360 mW
Thus: P
Dmax
= 443 mW
T
Jmax
for LQFP32 can be calculated as follows, using the thermal resistance Θ
JA
:
T
Jmax
= 82° C + (60° C/W x 443 mW) = 82°C + 27°C = 109° C
This is within the range of the suffix 3 version parts (-40 < T
J
< 131° C). In this case, parts
must be ordered at least with the temperature range suffix 3.
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STM8S105xxThermal characteristics