STM8S105C4 datasheet(107/121 Pages) STMICROELECTRONICS

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STM8S105x4/6

Thermal characteristics

107

12.2

Selecting the product temperature range

When ordering the microcontroller, the temperature range is specified in the order code (see

Section 13: Ordering information

The following example shows how to calculate the temperature range needed for a given

application.

Assuming the following application conditions:

Maximum ambient temperature TAmax= 82°C (measured according to JESD51-2),

IDDmax = 15 mA, VDD = 5.5 V

Maximum 8 standard I/Os used at the same time in output at low level with

IOL = 10 mA, VOL= 2 V

Maximum 4 high sink I/Os used at the same time in output at low level with

IOL = 20 mA, VOL= 1.5 V

Maximum 2 true open drain I/Os used at the same time in output at low level with

IOL = 20 mA, VOL= 2 V

PINTmax = 15 mA x 5.5 V= 82.5 mW

PIOmax = (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: PINTmax = 82.5 mW and PIOmax = 360 mW:

PDmax = 82.5 mW + 360 mW

Thus: PDmax = 443 mW.

Using the values obtained in Table 56: Thermal characteristics TJmax is calculated as

follows:

For LQFP32 60°C/W

TJmax = 82°C + (60°C/W x 443 mW) = 82°C + 27°C = 109 °C

This is within the range of the suffix 6 version parts (-40 < TJ < 131°C).

Parts must be ordered at least with the temperature range suffix 3.

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