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I'm a novice in hardware design so sorry about my 'newbish' question. I'm designing my first circuit that includes STM32L071KZU6 (datasheet) and I would like to know the 'worst' or maximum current consumption. I've seen this table in the datasheet: enter image description here

According to the table, it says that the total current of all VDD power lines (source) is maximum of 105mA. It sounds too much for the microcontroller and also it says that it is for 'source'.

Am I missing something?

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  • \$\begingroup\$ What you're looking for is in chapter 6.3.4 "Supply current characteristics" \$\endgroup\$
    – dim
    Jun 13 '18 at 13:09
  • \$\begingroup\$ Operating frequency planned, External interfaces, among others matters. You can explore STM32cube tool which is from ST and helps in estimating power easily \$\endgroup\$
    – User323693
    Jun 13 '18 at 15:06
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The table you have provided specifies absolute maximum currents and doesn't tell you anything about actual power consumption.

The actual power consumption for your application is strongly dependent on how you write your code and how active the processor will be. Additional power will be consumed if the processor IO pins are supplying current to loads. See section 6.3.4 in the data sheet for the gory details.

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it says that the total current of all VDD power lines (source) is maximum of 105mA

Actually that's not what this table is about.

Table 23 is in the section "6.2 Absolute maximum ratings" of the datasheet. These ratings are the voltages and currents which should never be exceeded. If you do so anyway you risk damaging the chip.

The current consumption of a chip like a microcontroller mainly depends on:

  • how fast you run it (clockspeed)

  • how much it is doing (more active means more current, power down/standby means less current).

  • how much current it needs to power other parts of the circuit

An example of that last point: if a GPIO pin needs to light up an LED directly, it might need to supply (source !) 5 mA. That 5mA needs to come through a VDD pin so it is part of that 105 mA max current. So power 21 LEDs at 5 mA and you're at that maximum. If you would use a MOSFET to switch on/off the LED then the GPIO pin only needs to charge/discharge the gate of that NMOS, that costs almost no supply current for the microcontroller.

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