TPS61088: How to calculate the output current

2313.TPS61088.pdf

Attached my sch. The input is0.9-2.4V  The VCC is5.5V。

Hi Ming,

I would suggest choose TPS61022 for this application.

Please follow the app note.

Hi Zack：

Do you have a way to estimate the current

Hi Ming,

Are you referring to input current or output current?

Hi Zack：

I mean output current.

Hi Ming,

You can use the equation to estimate output current.

Iout = Vin*Iin*Efficiency/Vout

Vin: input voltage 

Iin: maximum allowed input current. For boost converter, please check datasheet switch current limit spec and consider the inductor ripple

Efficiency: 80~90%

Vout: output voltage.

Dear Zack:

From the equation if  the I input is no limited the output should be limited by Inductor?

Back to my project my inductor current (RMS) is 6.7A, my output current should be 6.7*80%*Vin/Vout?

I cannot understand the datasheet typical application Why the sch of TPS61088 3.3 V to 9-V/3-A Output Converter current is 3A ?

Hi Ming,

Are you still wanting to use TPS61088? instead of TPS61022?

The datasheet typical application is just an example. We will leave some margin normally.

TPS61088 switch current limit is 10.6A minimum in PFM mode. Considering the inductor current ripple, the input average current has to be smaller than ~9A. Assume efficiency is 90%, maximum output current is 3.3V*0.9*9/9=2.97A.

Our customer wondered if this is a issue for output 3.9V(out of spec of 4.5V ).

This design is in mass production.  I want to estimate the output capacity. So my design output current  I out= 2.4V*1.5A*90%/3.9V=0.83A?

Where does the 1.5A come from?

Hi:

1.5A is input current limited.