Patent ID: 8804784

Claim:
A semiconductor laser driving device driving a semiconductor laser, the semiconductor laser driving device comprising: a driving current output terminal configured to output a driving current; a driving current monitoring terminal configured to output a driving current monitoring current having a value of 1/α, α≧1, of the driving current, the driving current monitoring terminal being connected in parallel with a line of the driving current output terminal and a power supply voltage; a detector configured to detect whether the driving current monitoring terminal has reached a reference voltage, wherein the driving current monitoring terminal is connectable to a current-voltage conversion resistor outside the semiconductor laser driving device, and the current-voltage conversion resistor is configured to convert the driving current monitoring current having the value of 1/α of the driving current into a corresponding driving current monitoring voltage; and a resistor disconnection detector configured to detect a disconnection of the current-voltage conversion resistor from the driving current monitoring terminal, wherein the detector for detecting whether the driving current monitoring terminal has reached the reference voltage is switched into a standby mode when the resistor disconnection detector detects the disconnection of the current-voltage conversion resistor from the driving current monitoring terminal and outputs a corresponding signal to the detector.