LP8758-E0 Abs-Max Current

Don Schelle

Hello,

I'm writing about the abs-max current located on page 5 of the datasheet.

The device is rated at 4A per output; but, if each output has 2x SW pins, then the maximum inductor current can not exceed 1.24A, thus limiting output current.

Some questions:

1. I notice that this is spec'ed at >10 year lifetime when operating at 125oC.

a. If the junction temperature is lower than 125oC, will this current be increased? If so, by how much?

b. Is there a graph that relates maximum current to expected lifetime of the device?

2. I suspect that this figure stems from electromigration in the solder bumps. Please confirm.

3. What's the failure mechanism if the above spec is exceeded? Cracks in the solder ball?

Don

over 8 years ago

0 Anssi Raisanen over 8 years ago

TI__Prodigy 250 points

Hi Don,

I will respond with email about this.

br,
Anssi Räisänen

0 Eric Steimle over 8 years ago in reply to Anssi Raisanen

Expert 2290 points

What was the answer here on maximum current? If the inductor current is limited to 1.24A how do I calculate what the maximum sustained output current is on any given channel for any given output voltage?

Thank you.

0 Tomi Koskela over 8 years ago in reply to Eric Steimle

TI__Genius 11020 points

Hello Eric,

With 125degC, 1.24A output current the lifetime would be the specified 100k hours. Output voltage does not effect this.

Hope this helps.

Thanks.

Best regards,
Tomi Koskela

0 Eric Steimle over 8 years ago in reply to Tomi Koskela

Expert 2290 points

Hi Tomi,

Thank you for answering all of my other questions. For this question I was asking what is the maximum output current per channel? The datasheet says 4A per channel but it also says the inductor current is limited to 1.4A. So then how can I pull 4A if the inductor limits the current to 1.4A?

Thank you

0 Tomi Koskela over 8 years ago in reply to Eric Steimle

TI__Genius 11020 points

Hello Eric,

Inductor current peak limit is 4.5A typical and buck output current is 4A typical.

In high temperature/stress conditions the electromigration rules need to be considered for the lifetime of the product and there the continuous current rating is specified as 0.62A/pin at 125degC temperature for 100k hours.

Hope this helps.

Thanks.

Best regards,

Tomi Koskela

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LP8758-E0 Abs-Max Current