STM32WB55CC datasheet(159/165 Pages) STMICROELECTRONICS

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DS11929 Rev 3

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STM32WB55xx

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As applications do not commonly use the STM32WB55xx 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 ambient 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 97 TJmax is calculated as follows:

–

For VFQFPN68, 47 °C/W

TJmax = 82 °C + (47 °C/W × 447 mW) = 82 °C + 21 °C = 103 °C

This is within the range of the suffix 6 version parts (–40 < TJ < 105 °C), see Section 8.

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

Section 8).

Note:

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

(order code suffix 7).

Suffix 7: TAmax = TJmax - (47°C/W × 447 mW) = 125°C -21°C = 104 °C

Example 2: High-temperature application

Using the same rules, it is possible to address applications that run at high ambient

temperatures with a low dissipation, as long as junction temperature TJ remains within the

specified range.

Assuming the following application conditions:

Maximum ambient 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 97 TJmax is calculated as follows:

–

For UFQFPN48, 51°C/W

TJmax = 100 °C + (51 °C/W × 134 mW) = 100 °C + 7 °C = 107 °C

This is above the range of the suffix 6 version parts (–40 < TJ < 105 °C).

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