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TPS61165: IC running hot

PeterF
Prodigy 70 points
Part Number: TPS61165

Hello!

At about 75% current the IC starts to run very hot and the brightness/current is not longer increasing. 

My layout is not ideal, might that be caused by that or have is miscalculated the current?

My power source is a 18650 LiIo cell, the IC was soldered with hot air.

The current is set with a 0.82 Ohm resistor to 240mA.

This is the circuit and layout:

  • 0
    TI__Intellectual 1780 points
    Hi Peter,

    In your schematic, the Ctrl pin is tied to Vin, which means the device is always running at full brightness.

    Your Rset of 0.82ohm for 240mA is correct. However, IC becoming hot could indicate that the current limit is getting triggered, which could happen if you exceed total power. What are your Vin & Vout conditions? If Vout/Vin ratio is large, the output current will be limited by switching current limit. Please review Page 10 of TPS61165 datasheet for equations and explanation on this section.

    Best,
    -Harini
  • 0 in reply to Harini Sankabattula
    Prodigy 70 points

    Thank you very much for your reply!

    V-in is a LiIo Cell, so the input voltage is around 3.5 to 4.2V with nominal 3.7V and the output voltage is around 13V, there are 4 white LEDs connected in series.

    I saw the information in the datasheet and it seems like i must have made a mistake when calculating it, is that correct?

  • 0 in reply to PeterF
    TI__Intellectual 1780 points

    Hi Peter,

    Yes, it seems to be quite close to the current limit. With not so perfect layout, efficiency may be low, which further limits the output current you can use. 

    Calculations are in the attachment. Also, below are a few suggestions on the components placement in your layout. As, it seems to be single layer, ground signal routing is still a challenge, but it is better in this configuration compared to what you've. 

    TPS61165_RVD.xlsx

    Best,

    -Harini