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Original question:

TPS92613-Q1: TPS92613QNDRRQ1

TPS92613-Q1: Input Capacitance

Akash S
Intellectual 750 points
Part Number: TPS92613-Q1

Hi,

We are planning to use TPS92613 in one of LED light designs. The datasheet suggests an input capacitance of 1uF. 

Due to some limitations, we are only allowed to use 0.47uF. Will it cause any issue?

The system characteristics is as below:

Input voltage: 12V

LED forward voltage: 8.25V

  • 0
    TI__Expert 4955 points

    Hello Akash, 

    For clarification, this would be the input capacitance correct? I would like to point out that the datasheet suggests 2 input capacitors, a small 100nF capacitor to provide filtering for high frequency noise, and a bigger 1uF to aid with EMI and ESD immunity. If you choose a smaller capacitors, these parameters might be affected. 

    Best,

    Pedro Arango Ramirez

  • 0 in reply to Pedro Arango Ramirez
    Intellectual 750 points

    Hi Pedro,

    We will be using the 100nF capacitor for filtering.

    For the bigger capacitor, we are limited to use only 0.47uF. We are not doing PWM. The driver would operate at 100% duty cylce only.

    Will we still face EMI issues? 

    Also there will be a 10E resistor at the input supply. Can this cause an issue?

  • 0 in reply to Akash S
    TI__Expert 4955 points

    Hello Akash, 

    Not using PWM will certainly help with EMI. Unfortunately I can not guarantee performance of the system without trace length knowledge and overall system considerations. These are calculations that you will need to perform based on the actual system. 

    Without seeing the entire systems I can't guarantee its functionality. 

    Best,

    Pedro Arango Ramirez

  • 0 in reply to Pedro Arango Ramirez
    Intellectual 750 points

    Hi Pedro,

    Please find the system architecture below:

  • 0 in reply to Akash S
    TI__Expert 4955 points

    Hello Akash, thank you for providing this information.

    The 10 Ohm resistor should not cause an issue, it will simply shift the corner frequency of the RC low pass filter that can be calculated with the resistor and capacitor values. The trace length seems small enough that I would not be overly worried with the trace inductance. With regards to the  smaller capacitor, if going outside the recommended parameters the EMI and ESD performance may be lowered. Whether  this is an acceptable trade off it is up for your engineering team to decide. 

    Best,

    Pedro Arango Ramirez