Laser driver with a safety circuit having digital feedback

摘要

A driver circuit for an opto-electrical transmitter includes a digital feedback loop. A counter in the feedback loop maintains a count that controls a bias current output to the opto-electrical transmitter. A first fault activation circuit in the driver activates a fault signal that disables the driver when the count causes an overflow or underflow. The overflow/underflow can correspond to the input range of an ADC that converts the count into an analog signal to an output amplifier or to the range of the counter. A second fault activation signal times the duration of any periods during which a digital parameter of the driver is outside a target range. The digital parameter can be a measured monitor current or the count that controls the output amplifier.