Battery charger failure

[FreshmanNewbie]

I'm using this Battery Charger IC - MCP73831.

I am using a SOT-23 package.

My input is 5V, the output Vbat charge regulated voltage on the Vbat pin is 4.2V and the maximum charge current is 340mA.

So, by calculation of power dissipation as per section 6.1.1.3 on page 18, it says that, for my condition,

Power Dissipation = (5V - 2.7V) * 0.34A = 782mW

Maximum junction temperature = (0.782 * 230degC/W) + 25deC (ambient) = 204degC approx.

Can you please check whether the layout is OK? Is grounding sufficient to reduce thermal dissipation?

My battery charger is burning and failing.


For the purpose of MOSFET, please see the below figure in this App Note

 

[stenzer]

Hi,

I only see a single layer here. So we do not see how the opposite site looks like, and how bottom and top layer are thermaly connected. Furteher, I do not see a single VIA placed in the copper areas close to the IC in question (U2). But for sure, the layout does not follow the recommendation in section 6.2, i.e. missing VIAs and VDD (pin #4) connection/area is quite "small".

The themal specifications table (page 5) indicates a better performance when using large copper areas. So connected the pins to large areas and use vias to distribute the heate to copper areas on the opposite site.

Further, the number of layers also contribute to the thermal performance, see [1] table 8.

[1] https://ww1.microchip.com/downloads/en/appnotes/00792a.pdf