TPS63000: Programming Vout with WeBench as reference

Chris Schramm

Part Number: TPS63000

Dear TI-Team,

actually, I'm not that much a hardware guy. I'm just building hardware to get our software running on it. So I was happy to see that there is a WeBench TPS63000 customizer / power designer.

Our requirement is converting a fixed 3.45V from a 3.7V (nominal) Li-Ion for a load < 1A.

So here are the parameters I've used in Power Designer:

Input DC: 3.0V - 5V (well, just in case)

Output: 3.45V at 0.8A

This gives Rfbb 162kOhm and Rfbt 1.05Mohm. So I've added ERJ-1GNF1623C (162kOhms) and CRCW04021M05FKED (1.05MOhms) - but I see 3.75V at Vout instead of 3.45V. I can measure 0.5V at FB pin.

What's my mistake? Please advise

Layout:

Schematic:

Webench:

over 5 years ago

0 Chris Schramm over 5 years ago

Intellectual 590 points

Okay, it seems there is an error in Webench.
I calculated with the Equation 1 and yes, for my resistors, I get around 3.75V

Using 200kOhm for Rfbb, I think 1.18M are required for Rfbt if I want 3.45V - can you please confirm?

0 Brigitte over 5 years ago in reply to Chris Schramm

TI__Guru 61215 points

Hello Chris,

You are right, for an output voltage of 3.45V, the resistor divider in the Webench design is not correct. Please excuse this failure, we will update the Webench tool.

0 Brigitte over 5 years ago in reply to Brigitte

TI__Guru 61215 points

Hello Chris,

The Webench tool is now updated with the right calculation formula for the resistive divider. Please excuse the inconvenience you had with this issue.

0 Chris Schramm over 5 years ago in reply to Brigitte

Intellectual 590 points

I just received the updated prototype.

This is the schematic:

But still, I only get 0.5V at Vout and I see a Iq of about 11mA for VIN=5V and 8mA for VIN=4V... what did I do wrong?

0 Brigitte over 5 years ago in reply to Chris Schramm

TI__Guru 61215 points

Hello Chris,

Now I am confused. You did get the output voltage set by the resistor divider in your first design, correct?

You only changed the resistor divider from the first design to the second one, is this correct? If there is only 0.5V on the output, is it possible that the top resistor is shorted?

0 Brigitte over 5 years ago in reply to Brigitte

TI__Guru 61215 points

Hello Chris,

I haven’t heard back so I’m assuming you were able to resolve your issue. If not, just post a reply below (or create a new thread if the thread has locked due to time-out).

Power management

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TPS63000: Programming Vout with WeBench as reference