TPS7A54-Q1: output accuracy calculation

Ben Kuo

Expert 7580 points

Part Number: TPS7A54-Q1
Other Parts Discussed in Thread: TPS568231, TPS7A54, TPS542A50

Dear team,

We would like to calculate device output accuracy for system design. But cannot find min/max value of VFB.

Does Vout accuracy in datasheet exclude feedback resistors tolerance?

If not, we should able to use Vout accuracy=VFB for our design.

If yes, what resistors tolerance you used to get this data?

Regards,

Ben

over 2 years ago

0 Juliette over 2 years ago

TI__Mastermind 18466 points

Hey Ben,

When the device is connected to external feedback resistors at the FB pin, external resistor tolerances are not included.

Feedback tolerance is also typically not measured because it does not take into account the entire control loop.

Best,

Juliette

0 CHIA CHOU HSU over 2 years ago in reply to Juliette

Prodigy 20 points

Hi Juliette,

So if we use 1% resistor for external voltage feedback, what is the total Vout tolerance?

Is that 1% for external loopback multiply 1% for Vout tolerance of TPS7A54-Q1 itself.

The total Vout tolerance would be (1.01*1.01) - 1 = 2.01%.

Is that correct?

Regards,

Joey

0 Juliette over 2 years ago in reply to CHIA CHOU HSU

TI__Mastermind 18466 points

Hey Joey,

A more precise way of approximate the effect on accuracy is delineated in this app note: https://www.ti.com/lit/an/slva423/slva423.pdf

Section 4 explains how to add the tolerances to the overall output accuracy.

The guidance on the DS to pick resistors is:

Best,

Juliette

0 CHIA CHOU HSU over 2 years ago in reply to Juliette

Prodigy 20 points

Hi Juliette,

Is there any method to get VFB tolerance from VOUT tolerance?

Some VRMs like TPS568231 provide the maximum and minimum value.

By using same parameter, this would be easier for us to check.

Regards,

Joey

0 Sourav Chakraborty over 2 years ago in reply to CHIA CHOU HSU

Prodigy 30 points

Exactly, completely agree with Joey, it will be wonderful to have Vfb tolerance for this part.

Thanks a lot

Regards

Sourav

0 Juliette over 2 years ago in reply to Sourav Chakraborty

TI__Mastermind 18466 points

Hello All,

For feedback tolerance, I think we are able to share (under an NDA) sigmas and means of the feedback shorted to VOUT. I will have to verify with the product engineers, however.

Best,

Juliette

0 Ben Kuo over 2 years ago in reply to Juliette

TI__Expert 7580 points

Hi Juliette,

Could you share this with me by mail? Thanks.

benkuo@ti.com

Regards,

Ben

0 Juliette over 2 years ago in reply to Ben Kuo

TI__Mastermind 18466 points

Hey Ben,

I included you in the email chain, I will go ahead an close out this thread.

Best,

Juliette

0 Sourav Chakraborty over 2 years ago in reply to Juliette

Prodigy 30 points

May we get the Vfb tolerance for this part (TPS7A54) ?

We also need to get the Vfb tolerance TPS542A50 as well.

Please help to get those answers ASAP.

0 Juliette over 2 years ago in reply to Sourav Chakraborty

TI__Mastermind 18466 points

Hey Sourav,

are you in contact with Ben? Are you under NDA?

Best,

Juliette

0 Sourav Chakraborty over 2 years ago in reply to Juliette

Prodigy 30 points

Hi Juliette

Yes,

Ben just send us some PPT file but we are asking Vfb tolerance in numbers.

So, still waiting for Ben to confirm us the Vfb tolerance in numbers for TPS7A54 and TPS542A50

Regards

Sourav

0 Juliette over 2 years ago in reply to Sourav Chakraborty

TI__Mastermind 18466 points

Hey Sourav,

Thank you for updating.

Best,

Juliette

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TPS7A54-Q1: output accuracy calculation