TPS563212: UVLO calculations

James VDC

Part Number: TPS563212

Hello,

I am trying to setup the UVLO and am following the formulas in the datasheet. Is there a MIN difference between VSTART and VSTOP? I do not see a specification for this, but am finding that my calculations for R1 always end up with a negative result. I was beginning with a desired VSTART of 12VDC and VSTOP of 11VDC.

Thank you for your assistance.

James

over 1 year ago

0 Zixu Wang over 1 year ago

TI__Expert 8100 points

Hi James,

I will check the calculation process and give you reply later!

BRs

Zixu

0 Zixu Wang over 1 year ago

TI__Expert 8100 points

Hi James,

Although there is no specific description for illustrating Min difference, the range of VSTART/VSTOP could be limited from the formula listed in datasheet.

The value of VSTART/VSTOP should be greater than value of VEN_FALL/VEN_RISE from above formula. Otherwise the calculated result of R1 could be negative.

BRs

Zixu

0 James VDC over 1 year ago in reply to Zixu Wang

Prodigy 240 points

Zixu,

Forgive me if I am mistaken, but that doesn't seem to work out either.

Vstart = 12
Vstop = 11

12/11 = 1.09
1.01/1.15 = 0.878

1.09 > 0.878

However, Vstart * (VEN_FALL/VEN_RISE)-Vstop
12 * (0.878) - 11 =
10.536 - 11 = -.464

Am I doing something wrong?

Thanks

0 James VDC over 1 year ago in reply to James VDC

Prodigy 240 points

I am wondering if it isn't something like:
VStop/.877 = MIN VStart ?

And, if that is the case, what is the minimum value permissible for R1?

0 Zixu Wang over 1 year ago in reply to James VDC

TI__Expert 8100 points

Hi James,

Sorry for the typo. The value of VSTART/VSTOP should be greater than value of VEN_RISE/VEN_FALL.

May I check what odes "VStop/.877 = MIN VStart" mean? Where do you get such formula?

At present, we may do not have such formula to regulate the value of MIN Vstart.

BRs

Zixu

0 James VDC over 1 year ago in reply to Zixu Wang

Prodigy 240 points

Zixu,

That makes more sense. Thank you.

Sure, what I did was simply work the calculation to result in a positive number for the numerator

(VStart * (VEnFALL/VEnRISE) - VStop)

VStart * 0.878 - VStop

So, VStart * 0.878 needs to be greater than Vstop

Therefore a simple way of getting without a lot of difference between: Vstop/0.877

0 Zixu Wang over 1 year ago in reply to James VDC

TI__Expert 8100 points

Hi James,

Yes, the formula you used is right.

There may be no permissible minimum value for R1. The value of R1 could be calculated from formulas in datasheet and please make sure the VEN is within the range of recommended operating condition.

BRs

Zixu

Power management

Power management forum

TPS563212: UVLO calculations