TPS82150: TPS82150 start up time

Naoki.N

Intellectual 515 points

Part Number: TPS82150

I want to ask about TPS82150's start up time.

I simulated TPS82150's start up sequence using PSpice for TI.

I made 5V,3.3V,1.8V,1.2V & 1.0V from 12V using this IC.

Start up sequence is below

1st start up :5V,1.0V

2nd start up:1.8V,1.2V (using PG made from 1.0V IC)

3rd start up:3.3V(using PG made from 1.8V IC)

I noticed that start up times are different of all voltage ICs.

Css/TR capicitor's value are 470pF in all voltage ICs.

According to the datasheet, I think that start up time will decide from Equation (7).

So I thought the time was the same for all voltages because the capacitors have the same capacitance. Can you tell me why they are different?

Best regards

Naoki

over 3 years ago

0 Lucia Gao over 3 years ago

TI__Mastermind 19350 points

Hi,

Nancy will help support this soon.

BRs

Lucia

0 Nancy Zhang over 3 years ago

TI__Mastermind 47020 points

Hi Naoki,

I will close this post and reply in the new post.

Thanks,

Nancy

0 Nancy Zhang over 3 years ago

TI__Mastermind 47020 points

Hi Naoki,

Sorry for late. Output voltage rise time is different with soft start ramp up time. The soft start ramp up time can be programmed by equation in the datasheet. the soft start voltage can only ramp up to 0.8V. This timing matched the equation for all different output voltages. But after the 0.8V, the output voltage rise time is not controlled by soft start. So 5V has longer rise time than 1.8V. Please see my simulation slide for detail.

Thanks,

Nancy

TPS82150 Soft start Pspice simulation.pptx

Power management

Power management forum

TPS82150: TPS82150 start up time