Datasheet

Package information STM32F091xB STM32F091xC
122/128 DocID026284 Rev 4
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 STM32F091xB/xC 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.
Example 1: High-performance application
Assuming the following application conditions:
Maximum temperature T
Amax
= 82 °C (measured according to JESD51-2), I
DDmax
= 50
mA, V
DD
= 3.5 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 and maximum 8 I/Os used at the same time in output at low level
with I
OL
= 20 mA, V
OL
= 1.3 V
P
INTmax
= 50 mA × 3.5 V= 175 mW
P
IOmax
= 20 × 8 mA × 0.4 V + 8 × 20 mA × 1.3 V = 272 mW
This gives: P
INTmax
= 175 mW and P
IOmax
= 272 mW:
P
Dmax
= 175 + 272 = 447 mW
Using the values obtained in Table 80 T
Jmax
is calculated as follows:
– For LQFP64, 45 °C/W
T
Jmax
= 82 °C + (45 °C/W × 447 mW) = 82 °C + 20.115 °C = 102.115 °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 (see
Section 8: Ordering information).
Note: With this given P
Dmax
we can find the T
Amax
allowed for a given device temperature range
(order code suffix 6 or 7).
Suffix 6: T
Amax
= T
Jmax
- (45°C/W × 447 mW) = 105-20.115 = 84.885 °C
Suffix 7: T
Amax
= T
Jmax
- (45°C/W × 447 mW) = 125-20.115 = 104.885 °C
Example 2: High-temperature application
Using the same rules, it is possible to address applications that run at high temperatures
with a low dissipation, as long as junction temperature T
J
remains within the specified
range.
Assuming the following application conditions:
Maximum temperature T
Amax
= 100 °C (measured according to JESD51-2), I
DDmax
=
20 mA, V
DD
= 3.5 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
= 20 mA × 3.5 V= 70 mW
P
IOmax
= 20 × 8 mA × 0.4 V = 64 mW
This gives: P
INTmax
= 70 mW and P
IOmax
= 64 mW:
P
Dmax
= 70 + 64 = 134 mW
Thus: P
Dmax
= 134 mW
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