Datasheet

UnitValueParameter
(1)
Symbol
°C/W
101
Thermal resistance junction-ambient
UFQFPN20 - 3 x 3 mm
Θ
JA
°C/W
60
Thermal resistance junction-ambient
LQFP32 - 7 x 7 mm
Θ
JA
°C/W38
Thermal resistance junction-ambient
Θ
JA
UFQFPN32 - 5 x 5 mm
°C/W60
Thermal resistance junction-ambient
Θ
JA
SDIP32 - 400 mils
(1)
Thermal resistances are based on JEDEC JESD51-2 with 4-layer PCB in a natural
convection environment.
Reference document11.8.1
JESD51-2 integrated circuits thermal test method environment conditions - natural convection
(still air). Available from www.jedec.org.
Selecting the product temperature range11.8.2
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
= 75 °C (measured according to JESD51-2)
•
I
DDmax
= 8 mA, V
DD
= 5 V
•
Maximum 20 I/Os used at the same time in output at low level with
I
OL
= 8 mA, V
OL
= 0.4 V
P
INTmax =
8 mA x 5 V = 400 mW
Amax
•
P
Dmax =
400
mW +
64 mW
Thus: P
Dmax
= 464 mW
T
Jmax
for LQFP32 can be calculated as follows, using the thermal resistance Θ
JA
:
T
Jmax
= 75 °C + (60 °C/W x 464 mW) = 75 °C + 27.8 °C = 102.8 °C
This is within the range of the suffix 6 version parts (-40 < T
J
< 105 °C).
In this case, parts must be ordered at least with the temperature range suffix 6.
103/116DocID15590 Rev 8
Package informationSTM8S903K3 STM8S903F3