• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 64 subscribers
  • Views 89 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS92638-Q1: Minimum Supply Voltage

Ömer Kalayci
Prodigy 175 points
Part Number: TPS92638-Q1
Other Parts Discussed in Thread: LM5164-Q1

Tool/software:

Hello,

I am thinking of supplying the “Supply” pin of the TPS92638-Q1 with a Buck converter (LM5164-Q1) with 5V output, will I have problems with the stability of the product?

I am worried about the minimum 5V supply, is it the right approach to run it by feeding it with 5V continuously?

I will connect a single 1 LED to the Iout pin with a voltage of 3.2V (I have attached a representative schematic below)

with my regards

  • +1
    TI__Genius 10285 points

    Hi Ömer,

    LED drivers are often supplied from the output of a buck converter.

    I am not familiar with the specific LM5164-Q1 device mentioned. If you have questions about the stability of the buck converter loop, feel free to direct the question to the DC converters team.

    I am worried about the minimum 5V supply, is it the right approach to run it by feeding it with 5V continuously?

    5V is the minimum operating supply voltage of the TPS92638-Q1. You must ensure that during the worst-case load transient (for example: all 8 channels enabled at the same time), the supply voltage does not dip below 5V.

    The transient voltage drop on the supply line is a function of the buck transient performance and the capacitance placed at the supply pin. You may consider placing additional bulk capacitance at the supply pin to help supply transient current and minimize the voltage drop.

    You may also consider increasing the output of your buck to 5.1V or 5.2V which will allow you to tolerate a 100-200mV drop on the TPS92638-Q1 supply line during a worst-case load transient. The tradeoff is that the increased supply voltage results in a slightly increased power dissipation and reduced efficiency. Depending on your requirements, this difference may be negligible.

    Regards,

    Zach

  • 0 in reply to Zach Olson
    Prodigy 175 points

    Hello Zach,

    Thank you very much for your answers, I need your help with one more thing.

    In the circuit I will design, there will be several variants, and in some cases, I need to avoid connecting certain LEDs, but I want the fault pin to work correctly.

    In some variants, the LED should not be placed, but I don't want it to be detected as an error (open load). Can I place a resistor where I shouldn't place an LED to make it think there is an LED and not give a fault? (Below, I have shown an example of an electronic connection.)

    At the same time, when I do this, the LED will have a 2.5V drop across the resistor for a 3.5V LED. Will this connection you made interfere with the PWM I will control from the MCU? (For example, if I drive the LED at 50% PWM, will it really be driven at 50%?)



    best regards





  • 0 in reply to Ömer Kalayci
    TI__Genius 10285 points

    Hi Ömer,

    I have addressed this question on your other thread: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1420095/tps92638-q1-minimum-supply-voltage 

    You may refer to the other thread and please avoid posting redundant questions to multiple threads as this makes it more difficult for us to track and support your questions.

    Thanks,

    Zach