Author Topic: AL8853AQ temperature  (Read 256 times)

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Offline NikWingTopic starter

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AL8853AQ temperature
« on: May 24, 2024, 02:08:06 pm »
Hello all!

after a long time of just lurking I'm back with a question about a LED driver IC from Diodes.
Maybe anyone here has an idea if something is wrong or if I could ignore what I think is a problem:

I've made me a small LED driver board to drive white SMD LEDs in series, using Diode's AL8853AQ IC, which uses an external MOSFET for switching.
The circuit is basically the one found in the datasheet (figure 1: Typical Boost Schematic for Constant Current Output Application)

It works, but I've noticed that the AL8853 is rather hot. Since it is not switching any load except the MOSFET gate, I wonder why it is hot and if this is a problem.
I don't see any information about the working temperature in the datasheet, except for the junction temperature over-temp protection:

Quote
Thermal Shutdown
The AL8853AQ includes a thermal protection circuit to ensure that the system will not run into condition of thermal runaway and blow up. When the junction temperature exceeds +160°C, AL8853AQ shuts down. And if the junction temperature falls below +135°C, AL8853AQ will automatically restart.

Does it mean the IC itself can get hot and I should not worry?

btw, personal opinion: I hate that these drivers need an external enable signal to start working. Why can't they just make use of an undervoltage shutdown function like normal DC/DC-converter drivers have? A simple voltage divider between VIN and GND and a threshold level and it will start as soon as it gets power from a PSU ... all my LED driver ICs (like AP3041 and AL3066) have this problem :/

Greetings,
Nik
 

Offline aliarifat794

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Re: AL8853AQ temperature
« Reply #1 on: May 24, 2024, 03:55:11 pm »
AL8853AQ should be properly heatsinked or mounted on a PCB with sufficient thermal vias to dissipate heat. If the IC is operating within its specified junction temperature range (usually provided in the datasheet), then it's likely functioning as designed.
 

Offline NikWingTopic starter

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Re: AL8853AQ temperature
« Reply #2 on: May 24, 2024, 06:11:38 pm »
yeah, it has no thermal pad at the bottom, so the only way is to do it via pin pads and groundplane, but usually there is some air gap below the chip SO8 case.
it's just a little hard to understand for me why a chip that does not switch any current become this warm (up to 160°C junction temp), so I thought I ask here for opinions :)
 


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