Power supply circuit, corresponding device and method

A system, comprising:

• an electrically powered device;
• and
• a circuit including:
• a first node configured to receive a first voltage;
• a second node coupled to provide electrical supply power to said electrically powered device;
• a first voltage regulator coupled to the first node and the second node and configured to provide a first regulated voltage at the second node;
• wherein the first voltage regulator is activatable in a first mode of operation for startup during which the first voltage regulator applies to said second node a voltage that increases towards a supply threshold;
• a power on reset circuit having an input receiving the voltage at said second node and configured to assert an enable signal when the increase of the voltage at said second node reaches the supply threshold;
• a second voltage regulator coupled to the first node and configured to provide a second regulated voltage at a third node, wherein said second voltage regulator is activated in response to assertion of the enable signal;
• and
• control circuitry powered by the second regulated voltage at the third node;
• wherein the control circuitry is configured, when the second voltage regulator is activated, to control a change of the first voltage regulator to a second mode of operation where a regulated voltage higher than said supply threshold is applied to said second node, and further configured, when low-power operation request signal is received, to control a change of the first voltage regulator to a third mode of operation providing low power operation at the second node and to deassert the enable signal to deactivate the second voltage regulator.