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Unused Sink pin of ADP8140


Can I leave unused sink pin unconnected? I am planning to use only one SINK pin.

What is the estimated product life time for ADP8140 device?


Rajesh Kumar

  • Hi Rajesh,

    It will depend on how you use the product. If you won't use the adaptive power control and no dimming, that should be ok. You may want to share your schematic so we can understand better. Typical application circuits in datasheet use the FB pin of the IC.

    This product is "Recommended for New Designs" so I don't see this coming out of ADI portfolio at least in next 5 years.

  • Hi Fil,

    Thanks for responding back.

    Application demands us to have two set of sinking requirements:

    For day light visibility, sinking current typical is 50mA and operating voltage is 28.5V+/-0.5V. However in night mode, sink current reduces to about 5mA, which we want to use PWM dimming either using DIM pin or VT pin. We are also interested to exercise Analog dimming during proto testing. So, we will have to go for dimming for sure. However we don't want to use power stage control for much use. In that case could you please confirm whether we can leave unused sink pins floating?

    Sure, we would like to share our circuit design in private message, is it possible?



  • Hi Rajesh,

    I'm not sure if you can leave unused pins floating as you may have issue with the feedback control. If you want to try this, please get a demo board that a proto with your design. Would you have volume opportunity for this project?

  • Thanks for responding back.

    I would like to summarize our application as below:

    1. LED operating current is typ 50mA and can be reduced to 5mA using PWM dimming preferrably.

    2. We have only one LED module, so require only one sink pin to be used.

    3. Preferred mode of operation will be PWM EA operation by connecting mode pin to REG.

    With respect to above, can we leave unused sink pin floating. We don't want to use FB_OUT and FAULT pin of the device. We have external control mechanism to control the power stage. We are planning to use this device as sinking the LED current.

    How do we share our schematic for review? Can you provide your mail id?