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TPS61165: Please review the schematic

Chase Jeong
Genius 5440 points
Part Number: TPS61165

Dear TI experts,

My customer now tests TPS61165 with their own PCB.

Could you review the schematic first?

input : 12V

output : 24V

LED current consumption : 1A @ 24V

LED turns on and off every 100m seconds.

the problem is, measured output voltage is about 20V, not 24V.

they changed the value of R119 to 0.2 ohm, output voltage is up to 21V, but it is still not 24V.

Could you tell me the reason why the output voltage is not going up to 24V?

(How about 10uH inductor? is there any possibility that inductor is the reason?)

Best regards,

Chase

  • 0
    Genius 5440 points

    Dear  experts,

    I have some updates from customer;

    1. They changed 10uH inductor to having larger current rate. the result was same.

    2. They used 2 TPS61165s in parallel, so they expected larger output current.

    The result was -> output voltage was 23.3.V, still not reached to 24V.

    output voltage was 20.4V when using 1 TPS61165.

    Please check this issue. Thanks.

    Best regards,

    Chase

  • 0
    TI__Mastermind 27000 points

    Hi Chase,

    For the initial condition, when the R119 change to 0.2ohm, what is the LED current customer measured?

    BR

    Patrick

  • 0 in reply to Patrick Yao
    Genius 5440 points

    Dear Patrick,

    Thank you for your support.

    unfortunately They do not have the way to measure LED current. (i.e. current probe.) That's why i gave you only input voltage and current from power supply.

    anyway I have more questions from my customer.

    1. I found that internal FET has 1.2A switch current limit. Is it okay to operate 1A current LED?

    (because I also saw that LED current per channel is 400mA in the product webpage. and what is the meaning of 3 LEDs on the first page of datasheet?)

    2. output LED voltage is only controlled by 1 resistor, Rset.

    what is the formula to calculate output voltage?

    I am asking you this because I think that it would be have different Rset value if input voltage is different (i.e. 12V and 18V) even output voltage is the same.

    is Rset value same both input voltage is 12V and 18V even the output voltage is 24V?

    3. If TPS61165 is not suitable for driving 1A current LED, please recommend other IC. (cheaper one)

    Please check these issues. Thanks.

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Mastermind 27000 points

    Hi Chase,

    1. Yes you are right, the current limit is not enough to drive a 1A LED with voltage ratio 12V to 24V.

    2. The output voltage will adjust based on LED Vf. Rset is used to set LED current, not output voltage. So if you need same current with 12V and 18V input, the Rset should be the same.

    3. Please allow me some time to find other solutions.

    BR

    Patrick

  • 0 in reply to Patrick Yao
    Genius 5440 points

    Dear Patrick,

    Thank you for your support.

    Please let me know if you fined any suitable LED driver for my customer.

    and one more question;

    I cannot find of the content which LED current per channel is 400mA in the datasheet. Where can I find it?

    Best regards,

    Chase

  • 0 in reply to Chase Jeong
    TI__Mastermind 27000 points

    Hi Chase,

    It is not listed in datasheet.

    BR

    Patrick