Laser-driven open circuit detection circuit

Abstract

The invention discloses a laser driving open circuit detection circuit which comprises a laser driving circuit, a laser device LD, a resistor RT, a resistor Rs, a third constant current source IT and a comparer COMPARATOR, the resistor RT and the third constant current source IT are connected in series, the two ends of the resistor RT and the third constant current source IT are connected between the positive end of a resistor Rterm and the ground, one end of the resistor RT is connected with the positive end of the resistor Rterm, and the other end of the resistor Rs is connected with the positive end of the resistor Rterm. One end of the resistor RT is connected with the negative end of the resistor Rterm, the other end of the resistor RT is connected with the third constant current source IT and one input end of the comparator COMPARATOR, one end of the resistor Rs is connected with the negative end of the resistor Rterm, the other end of the resistor Rs is connected with the other input end of the comparator COMPARATOR, the voltage of the other end of the resistor RT is the voltage Vref1, the voltage of the other end of the resistor Rs is the voltage Vout1, and by comparing the voltage Vref1 with the voltage Vout1, the voltage of the other end of the resistor Rs is calculated. And judging whether the laser driving circuit is open-circuited with the laser LD or not. The device has the advantages that laser driving open circuit detection is realized easily, power failure or external detection tools are not needed, and normal work of the laser driving circuit and the laser is not affected.

Description

technical field [0001] The invention relates to a detection circuit, in particular to a laser-driven open circuit detection circuit. Background technique [0002] In the production process of the laser driver module (especially in the packaging and bonding process of the laser LD and the driver chip) or in the use stage of the laser driver module (due to external force factors or others), there will be a disconnection between the driver chip and the laser LD. The phenomenon of turning on, so that the driving current cannot flow into the laser LD normally, and the laser LD does not emit light. However, powering off the driver module and using a third-party testing tool can detect the open circuit problem between the driver chip and the laser LD, but this method is obviously time-consuming and resource-intensive. In order to reduce the detection time and cost of open-circuit bonding, it is necessary to design a detection circuit inside the driver chip that can automatically d...

AI Technical Summary

Problems solved by technology

[0005] 1. Connecting a resistor in series with the output terminal of the laser LD will reduce the modulation current of the laser LD

[0006] 2. Connecting a resistor in series with the laser LD at the output end will consume a certain voltage margin and generate unnecessary energy consumption at the same time

[0007] 3. A resistor connected in series with the laser LD at the output end will affect the performance of the drive current (rise and fall time, amplitude, etc.)

[0008] 4. The presence of parasitic capacitance at the input of the DIFF_AMP amplifier will also affect the bandwidth of the drive circuit, which in turn affects the rise and fall time of the drive current, etc.

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