LP55231: Excessive Heat

Hi,

Nice to hear you.

For your questions, could you also measure the Vin and Vout, because these 2 values could affect the thermal performance.

Besides, you mentioned that the board size is restricted, so I really want to recommend you our newest device LP5813, this device has integrated boost function and can control up to 12 LEDs with only 4 output pins, which means the size is very small compared to LP55231, about 1.4 x 1.8mm. And this device also has auto animation function, the most important thing is that the new device is based on our newest manufacturing process, which will have better thermal performance compared to LP55231.

If you want more information about LP5813, please contact me by message, and we can discuss more.

Thanks!

BR,

Ives Li

Hello,

We are pretty ahead in our development with LP55231 and we would prefer not to change the IC.

Is this a typical behavior of the IC? How can I avoid this thermal risks? 

Is it a known issue with this chip? Adding passive dissipation might improve it?

I saw some pptx about the proposed alternative but it uses big coils, isn't it? I will also need 2 of them as I have 6 RGB LEDs. Is there a new version with more outputs?

Have you got any pictures/graphs for the thermal heating of this new IC when full brightness is used?

Thank you very much

Hi,

For your questions:

Is this a typical behavior of the IC? How can I avoid this thermal risks? 

- Considering the board size is very small, so if you want to use the maximum output, the temperature rise could be high.

- To avoid this thermal risk, what you can do is:

   1. Use 4 layers board 

   2. Reduce the output current, because the recommend charge pump load current is 100mA, for 6 LEDs, each output could be 15mA.

   3. Reduce the input voltage.

   4. Connect a thermal sharing resistor with LEDs.

   5. Set charge pump to bypass mode could reduce temp rise if VDD is higher than the LED forward voltage. 

Is it a known issue with this chip? Adding passive dissipation might improve it?

- It is not a known issue with the chip, adding passive dissipation might improve it.

I saw some pptx about the proposed alternative but it uses big coils, isn't it? I will also need 2 of them as I have 6 RGB LEDs. Is there a new version with more outputs?

- Yes we have device LP5018 and LP5861 could control 18 channels' output, which means can control 6 RGB with 1 device.

Have you got any pictures/graphs for the thermal heating of this new IC when full brightness is used?

- We haven't test the temp rise because the result could be different on different boost voltage setting, an if you can provide more details about your applications, I could help you test the temp rise.

Besides, I also want to know more details to help you solve this thermal issue, could you provide:

- input voltage VDD

- output voltage VOUT

- LED forward voltage in 15mA/25mA

That will be helpful to keep solving this problem.

Thanks!

BR,

Ives Li

Hello,

My board already is a 4 layer board.

I checked the current and your are right. I am using 9 LEDs so if I put max brightness in all outputs I am exceeding the max current.

For my application I should limit the current to 10mA per LED which is a 40% of the maximum output current per channel.

If Vdd is higher than the Vf of my LEDs can I use more current while bypassing the charge pump?

I am using a RGB LED with Vf = 2.4V for RED and Vf = 3.1V for BLUE and GREEN.

Thank you

Hi 

For your application, you can use typical 3.3V power supply and bypass the charge pump, I think that will help you to minimize the temp rise.

You can try that working condition with 10mA for each channel on your board to test the thermal performance again.

Thanks!

Ives