real operating temp of LM1875

Daniele Nardi

Other Parts Discussed in Thread: LM1875

Hi,
I have to replace the ST's TDA2030 in an automotive application for obsolescence of the component.

I've successful tested the pin-to-pin compatible TI's LM1874, but I need to know the really operative temperature range:
on product's page description is specified "0 - 70°C"
datasheet's maximum ratings say "-65 - +150°C" of storage temp and "150°C" of junction temp

Than:
- if the limit is on the junction, can I consider to work at 85°C with a proper termal dissipation?
- if my previous hypotesis is true and than the "0 - 70" description is not true, what is the minimun operating temp?

Thank

over 8 years ago

0 Andy Liu (BMS) over 8 years ago

TI__Guru 52115 points

Hi Daniele,

I will take a look at your question and get back to you soon.

Andy

0 Andy Liu (BMS) over 8 years ago in reply to Andy Liu (BMS)

TI__Guru 52115 points

Hi Daniele,

The operating temperature depends on supply voltage, load resistor and heat sink thermal resistance.
Here is an equation about allowable power dissipation.
Pdmax=(Tjmax-Ta)/(θjc+θca)
Where
Pdmax: Maximum allowable power dissipation
Tjmax: Maximum junction temperature, in this case it is 150 degC
Ta: Ambient temperature.
θjc: Junction to case thermal resistance.
θca: Case to ambient thermal resistance.

So if you know the maximum power dissipation of your system, then you can calculate the operating temperature range by this equation. In addition, you can find more details on the Page 8 of LM1875 datasheet.

Andy

0 Daniele Nardi over 8 years ago in reply to Andy Liu (BMS)

Prodigy 140 points

Perfect, as I suppose. And what is the minimum operative temp?

0 Andy Liu (BMS) over 8 years ago in reply to Daniele Nardi

TI__Guru 52115 points

Hi Daniele,

The operating temperature is not specified in the datasheet. To find out the actual operating temperature range, you must know what kind of heat sink you will use and the power dissipation.

Andy

0 Daniele Nardi over 8 years ago in reply to Andy Liu (BMS)

Prodigy 140 points

It's impossible! TI must specify the MINIMUM operative temperature!
Can LM1875 work at 0°C? And -20°C? And -40°C? And -60°C...? It do not depend from my heatsink, but from TI's manufacturing processes.

Thank

0 Andy Liu (BMS) over 8 years ago in reply to Daniele Nardi

TI__Guru 52115 points

Hi Daniele,

I think I just misinterpreted your question. I thought you were still asking the temperature range (Both min and max). As for the
MINIMUM operating temperature, unfortunately it is NOT specified in the datasheet. However, my opinion is it should be 0°C.

Andy

0 Daniele Nardi over 8 years ago in reply to Andy Liu (BMS)

Prodigy 140 points

Thank Andy for your interest.

Can you ask this for me in TI?

0 Andy Liu (BMS) over 8 years ago in reply to Daniele Nardi

TI__Guru 52115 points

Hi Daniele,

We got a similar question a few days ago. My colleague has already confirmed with our QA team that we don't have the absolute maximum ratings on operating temperature.

Andy

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real operating temp of LM1875