An issue about ADN2871

The positive pole of DFB laser  should be connected with Case GND, however the figure below shows that the positive pole is connected with VCCC,  i wonder reason for it, and whether or this chip is suitable for this application. If it is not, is any other one suitable.

Parents
  • Dear Peng,

    Your selected laser module is in a butterfly package with the laser anode pin connected to the case ground.

    There are two ways to use this laser module with ADN2871:

    1.     Connecting the laser module case ground to supply Vcc. This keeps the "positive supply" design

            and you can use Fig. 29 circuit directly; or

    2.     Using "negative supply" way to ADN2871 circuitry. In the Fig. 29 circuit, change all external Vccs to new

            "negative supply" ground, change all external GNDs to -3.3V. Now, you can connect the laser module case

             to negative supply ground. In this way, you may have to pay attention to the ADN2871 control/monitor signal

             levels accordingly. Please note, in this case, all these DC levels are referred to -3.3V, not the ground.

    Hope these are what you need.

    Best Regards,

    Dongfeng Zhao


Reply
  • Dear Peng,

    Your selected laser module is in a butterfly package with the laser anode pin connected to the case ground.

    There are two ways to use this laser module with ADN2871:

    1.     Connecting the laser module case ground to supply Vcc. This keeps the "positive supply" design

            and you can use Fig. 29 circuit directly; or

    2.     Using "negative supply" way to ADN2871 circuitry. In the Fig. 29 circuit, change all external Vccs to new

            "negative supply" ground, change all external GNDs to -3.3V. Now, you can connect the laser module case

             to negative supply ground. In this way, you may have to pay attention to the ADN2871 control/monitor signal

             levels accordingly. Please note, in this case, all these DC levels are referred to -3.3V, not the ground.

    Hope these are what you need.

    Best Regards,

    Dongfeng Zhao


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