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Original question:

TPS92613-Q1: Input Capacitance

TPS92613-Q1: Cout capacitor

Akash S
Intellectual 790 points
Part Number: TPS92613-Q1
Other Parts Discussed in Thread: TPS92629-Q1

Hi,

We are designing a system where the LED would be placed 100meters away from the driver as shown in the image below:

Can you pls advice where the Cout capacitor should be placed, close to the driver or to the LED?

  • 0
    TI__Expert 4955 points

    Hello Akash, 

    That is certainly an interesting application. Conventional wisdom would say to put a small capacitor near the output pin and a larger capacitor near the load. However I do not believe that conventional wisdom alone can fully apply to this. 

    What End Equipment are you working on that you need 100m of cable from the output to the load?

    What input voltage are you supplying to the part? 

    Are you planning to use PWM dimming? Shunt FET dimming? Are there any other design considerations for this?

    What is the voltage drop per LED and what specific LEDs are you planning on using? 

    I ask all of this questions as this is an automotive part, where we do not see large traces or cables as this. 100m of cable will add considerable inductance and resistance which might heavily affect the performance and even usability of the part. Please answer my questions above and I will be able to help with your design or perhaps point you towards a more appropriate part in the LED Display Lighting portion of our portfolio that has various industrial applications. 


    Best,

    Pedro Arango Ramirez 

  • 0 in reply to Pedro Arango Ramirez
    Intellectual 790 points

    Hi Pedro,

    Thanks for the response.

    It is an industrial product where the LED light will be placed at the far end from the power supply. We will be using 12V power supply.

    We will not be using PWM dimming. The LED current will be fixed as determined by the Rsns shunt resistor.

    Can I share the LED details and cable specifications over a private window to maintain confidentiality?

  • 0 in reply to Akash S
    Intellectual 790 points

    Hi Pedro,

    Please find the details below:

    LED forward voltage = 8.25V

    Cable parameters at 100meters

    Resistance = 5.2 ohm

    Inductivity = 52uH

    Mutual capacitance = 16nF 

  • 0 in reply to Akash S
    TI__Expert 4955 points

    Hello Akash,


    Seeing how it is an industrial product, let me assign this thread to our industrial product line, as they might have insight on possible better solutions. The information you provided will be helpful for them to determine and understand your system. 

    Best,

    Pedro Arango Ramirez

  • 0 in reply to Pedro Arango Ramirez
    Intellectual 790 points

    Hi Pedro,

    So is this driver not suitable for use with long cable lengths?

    Can you pls help us make a decision?

  • 0 in reply to Akash S
    Intellectual 790 points

    Hi,

    One of the similar parts TPS92629-Q1, supports having long wire between the driver and LED. So, can we assume that TPS92613-Q1 will also be suitable for the same?

  • 0 in reply to Akash S
    TI__Expert 4955 points

    Hello Akash, 

    I believe that there might be better parts in the Display Lighting sector of our product line as they have much more experience dealing with non automotive applications. I will assign this thread to that team. Please wait for a response on their part. 


    Best,


    Pedro Arango Ramirez

  • 0 in reply to Akash S
    TI__Mastermind 33920 points

    Hi Akash,

    May I know the number of your LED string and the LED current as well?

    BR

    Patrick

  • 0 in reply to Patrick Yao
    Intellectual 790 points

    Hi Patrick,

    There is only one LED @8.3V forward voltage and the LED current would be 130mA

  • 0 in reply to Akash S
    TI__Mastermind 33920 points

    Hi Akash,

    Unfortunately we might not have a suitable device for your application. The cable inductance is a challenge for our devices.

    BR

    Patrick