How to use a laser driver designed for floating diodes with a diode that has its anode or its cathode connected to the case?

It is possible to drive a diode with the anode or the cathode connected to the case as long as you electrically isolate the case from the ground of the driver.

For the CTL101 Low noise butterfly laser diode controller and the CTL200 Digital butterfly laser diode controller, you can isolate the case from the circuit ground by relying on the electrical isolation of the baseplate anodization layer and by using the provided Nylon screws to attach the laser.

Before powering the driver, check that the resistance between the case and the circuit ground is higher than 10 kΩ.

What happens in case of a short circuit between the case and the circuit ground ?

When the anode is connected to the case (left in the figure below) no current pass through the diode.

When the cathode is connected to the case (right in the figure below), the current pass through the diode while being unregulated. The only protection remaining is the current limit. In most situations, the diode will be damaged.

If you need confirmation a driver is compatible with your laser, please contact us.

See also

• Understanding the basics of laser diode drivers