STM32F071X8 datasheet(116/122 Pages) STMICROELECTRONICS

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STM32F071x8 STM32F071xB

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As applications do not commonly use the STM32F071x8/xB 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 TAmax = 82 °C (measured according to JESD51-2), IDDmax = 50

mA, VDD = 3.5 V, maximum 20 I/Os used at the same time in output at low level with IOL

= 8 mA, VOL= 0.4 V and maximum 8 I/Os used at the same time in output at low level

with IOL = 20 mA, VOL= 1.3 V

PINTmax = 50 mA × 3.5 V= 175 mW

PIOmax = 20 × 8 mA × 0.4 V + 8 × 20 mA × 1.3 V = 272 mW

This gives: PINTmax = 175 mW and PIOmax = 272 mW:

PDmax= 175 + 272 = 447 mW

Using the values obtained in Table 77 TJmax is calculated as follows:

–

For LQFP64, 45 °C/W

TJmax = 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 < TJ < 105 °C).

In this case, parts must be ordered at least with the temperature range suffix 6 (see

Section 8: Part numbering).

Note:

With this given PDmax we can find the TAmax allowed for a given device temperature range

(order code suffix 6 or 7).

Suffix 6: TAmax = TJmax - (45°C/W × 447 mW) = 105-20.115 = 84.885 °C

Suffix 7: TAmax = TJmax - (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 TJ remains within the specified

range.

Assuming the following application conditions:

Maximum temperature TAmax = 100 °C (measured according to JESD51-2), IDDmax =

20 mA, VDD = 3.5 V, maximum 20 I/Os used at the same time in output at low level with

IOL = 8 mA, VOL= 0.4 V

PINTmax = 20 mA × 3.5 V= 70 mW

PIOmax = 20 × 8 mA × 0.4 V = 64 mW

This gives: PINTmax = 70 mW and PIOmax = 64 mW:

PDmax = 70 + 64 = 134 mW

Thus: PDmax = 134 mW

Using the values obtained in Table 77 TJmax is calculated as follows:

–

For LQFP64, 45 °C/W

TJmax = 100 °C + (45 °C/W × 134 mW) = 100 °C + 6.03 °C = 106.03 °C

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