TPS54531: Vstart and Vstop calculation review

PYTsai

Part Number: TPS54531

We would like to design VSTART=5.5V and VSTOP=5.0V

after calculation we get R10 =167K, R11=47.2K and our schematics as below.

However, using the above R10 and R11 value to do real test we see VSTART=6.33V and VSTOP=5.2V. this is different from our calculation result.

Would you help review anything wrong with our schematics below ?

Also is it required that Vin need to be > Vout + 2V ?

0 Shawn Nie over 5 years ago

Hi,

Could you please share the startup and shutdown waveforms (VIN,VOUT,SW)?

And it would be better to share the layout, let's review it.

Shawn

0 PYTsai over 5 years ago in reply to Shawn Nie

Hi Shawn,

While we are preparing the waveform, may i ask a quick question.

if our target Vout is 5V, what is the minimum voltage requirement for the Vin ?

0 Shawn Nie over 5 years ago in reply to PYTsai

Hi,

It is hard to say, it is related to the load current. What is the load current?

Shawn

0 PYTsai over 5 years ago in reply to Shawn Nie

Hi Shawn,

The load current is 5A ?

We are wondering our problem might related Vin voltage not enough. thanks!

0 Shawn Nie over 5 years ago in reply to PYTsai

Hi,

Is there any update?

Shawn

0 PYTsai over 5 years ago in reply to Shawn Nie

Hi Shawn,

The load current is 2A ~ 3A

Thanks!

0 Shawn Nie over 5 years ago in reply to PYTsai

Hi,

How about the Vstart and Vstop issue? Is there any waveform?

Shawn

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