Deployment circuit for a pyrotechnic device, corresponding integrated circuit, vehicle and method

A deployment circuit for a pyrotechnic device, the deployment circuit comprising:

• a pair of terminals couplable to the pyrotechnic device;
• a positive terminal and a negative terminal configured to receive a supply voltage;
• a driver circuit configured to selectively energize the pyrotechnic device, the driver circuit comprising:
• a first current limiter coupled between the positive terminal and a first terminal of the pair of terminals, the first current limiter configured to limit current flowing to the pyrotechnic device via the pair of terminals to a first maximum value,
• a second current limiter configured to limit current flowing to the pyrotechnic device via the pair of terminals to a second maximum value, the second maximum value being less than the first maximum value,
• a first electronic switch configured to selectively couple the second current limiter between a second terminal of the pair of terminals and the negative terminal as a function of a measurement control signal, and
• a second electronic switch configured to selectively couple the second terminal of the pair of terminals to the negative terminal as a function of a deployment control signal;
• and
• a control circuit configured to:
• drive the driver circuit as a function of a fire request signal,
• determine a resistance value of the pyrotechnic device via the pair of terminals by:
• configuring the first current limiter to limit current to the second maximum value,
• asserting the measurement control signal, and
• obtaining a voltage value indicative of a voltage at the pair of terminals,
• wherein the resistance value corresponds to the voltage value, the voltage value divided by a predetermined current value, or the voltage value divided by a measured current value indicative of current provided via the pair of terminals.

A method of operating a deployment circuit for a pyrotechnic device, the method comprising:

• coupling a pair of terminals of the deployment circuit to the pyrotechnic device;
• driving a driver circuit as a function of a fire request signal;
• starting a deployment cycle by asserting a deployment control signal in response to the fire request signal being asserted, wherein a deployment current flowing to the pyrotechnic device via the pair of terminals is current-limited to a first maximum value;
• monitoring a time duration corresponding to the deployment current exceeding a current threshold;
• stopping the deployment cycle after a predetermined time period by de-asserting the deployment control signal;
• determining a first resistance value of the pyrotechnic device via the pair of terminals;
• and
• generating a successful deployment signal in response to the time duration being greater than a time threshold and the first resistance value being greater than a first resistance threshold.