# How to Find the consecutive Temperature with input current for a charging IC?

Thread Starter

#### Redwan

Joined Dec 21, 2015
7
Hello there!

I have a problem in finding the relative temperature whenever different Current is pushed as input of the charging IC. IC number is PT116, I have used this in one of my mobile pcb for charging. Current drawing in output point of IC is 1 ampere, 1.5 ampere and 500 mA in Always 4.1volt DC. Input parameter is always same: 5volt,2Amp DC.

Now, when (1amp, 1.5amp,500mAmp), how much temperature will produce in the IC, can be calculated? I have seen the product's data sheet. It has a only a volt-temp curve,which is not helping me much. Urgent Help needed.

Thanks in Advance.

#### Dodgydave

Joined Jun 22, 2012
9,956
To calculate the Wattage, multiply the voltage drop across the ic, by the output current.

So if your input is 5v output is 4.1v,so
the volt drop is 0.9v x
0.5 amp = 0.45W,
1amp = 0.9W,
1.5amp = 1.35W.

Thread Starter

#### Redwan

Joined Dec 21, 2015
7
To calculate the Wattage, multiply the voltage drop across the ic, by the output current.

So if your input is 5v output is 4.1v,so
the volt drop is 0.9v x
0.5 amp = 0.45W,
1amp = 0.9W,
1.5amp = 1.35W.

Thanks @Dodgydave .Now how about finding the correspondent temperature? I have somehow managed a page of datasheet with relevant temperature curve. Can you tell me how to solve it?

#### Sensacell

Joined Jun 19, 2012
2,838
The temp rise depends on the thermal resistance of the board that the part is mounted on.

Not an easy thing to calculate at all- don't expect a simple equation to provide a meaningful answer.
Even sophisticated thermal analysis programs can produce garbage results if the any of the many input assumptions are wrong.

Airflow, position, materials all have subtle but significant impacts on the results.

Thermal analysis is tricky- but the first step is a ball park estimate of the thermal resistance of the circuit board it's mounted on.

• Redwan
Thread Starter

#### Redwan

Joined Dec 21, 2015
7
The temp rise depends on the thermal resistance of the board that the part is mounted on.

Not an easy thing to calculate at all- don't expect a simple equation to provide a meaningful answer.
Even sophisticated thermal analysis programs can produce garbage results if the any of the many input assumptions are wrong.

Airflow, position, materials all have subtle but significant impacts on the results.

Thermal analysis is tricky- but the first step is a ball park estimate of the thermal resistance of the circuit board it's mounted on.

I do 100% agree with you. But Can you give me any idea, how can at least I assume approximate value for the temperature?

#### Sensacell

Joined Jun 19, 2012
2,838
If it's an SOIC-6 dissipating 1.35 watts- it's going to get really hot.
Does it have a thermal pad on the bottom?

The only way to dump that much heat out of that small package is with a thermal pad stitched with many vias to a solid copper ground plane of several square inches.

Edit- looked at the data sheet- you are way off on something, the device can only handle 420 mW of power dissipation soldered to the "Standard Land Pattern"

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