LM5116: UVLO Calculation and output results

Bindu Subramanyam

Part Number: LM5116

Tool/software:

Hello TI,

Iam Designing a a buck converter using LM5116

Help me out in designing UVLO
How to calculate Ruv1 and Ruv2 and what should be the expected voltage and current at UVLO pin
Design values

Input Voltage-Vin=50V~60V
Output Voltage-Vout=5.2V
Output Current=10A
Output Ripple voltage=100mV expected
Efficiency-ɳ=95% expected
Switching Frequency=250kHz fixed w.r.t to the application circuit in datasheet.

I have used this formula for calculation. but couldn't solve it.

Thanking you,

K Bindhu.

13 days ago

0 EricLee 12 days ago

TI__Mastermind 49671 points

Hello Bindhu

You can download the Quick Start calculator at https://www.ti.com/lit/zip/snvu051 . Please check the VIN UVLO Shutdown in Step 7

-EL

0 Bindu Subramanyam 12 days ago in reply to EricLee

Prodigy 60 points

Hello EricLee

I have checked the calculator

Ruvlo1 has given a different value and Ruvlo2 is fixed.

1. What is the calculation of Ruvlo2. Is it fixed for all the design

2. How did we finalize ruvlo2

3. How will I know the min Voltage value of uvlo

Thankyou

K Bindhu

0 EricLee 12 days ago in reply to Bindu Subramanyam

TI__Mastermind 49671 points

Hello Bindhu

Can you change RUV2 value ? If you change RUV2 value, then RUV1 value will be calculated automatically.

-EL

0 Bindu Subramanyam 12 days ago in reply to EricLee

Prodigy 60 points

Hello Eric

1. Can you explain How Ruv2 is calculated. As per above represented formula i got Ruv2>500 x Vin-max; Ruv2>500 x 60; Ruv2>30kohm
2. As 7.2.2.12 to calculate Ruvlo1 I need to Know Ruv2 value and VIN-min (UVLO desired shutdown voltage)
3. how exactly should I calculate Ruvlo2 and on what condition i should set VIN-min?

Thank you

K Bindhu

0 EricLee 11 days ago in reply to Bindu Subramanyam

TI__Mastermind 49671 points

Hello Bindu

RUV2 is the user input. RUV1 is automatically calculated by the Quick Start. VIN(MIN) is the desired shutdown voltage which should be less than the minimum input supply voltage.

-EL

0 Bindu Subramanyam 11 days ago in reply to EricLee

Prodigy 60 points

Hello Eric

Correct me if iam wrong

1. So my Ruv2 can be >30kohm (so randomly can I consider it as 32kohm)

2. Vin-min as per the datasheet 7.2.2.12 it is given the shutdown voltage cannot be greater than 16V

I have input voltage of 40 ~50V

In this condition what should I keep vin-min as? How to select vin-min

Thankyou

K Bindhu

0 EricLee 10 days ago in reply to Bindu Subramanyam

TI__Mastermind 49671 points

Hello Bindu

1. Correct

2. VIN(MIN) is also an user input , which should be less than the minimum input supply voltage.

For example, you can select 30V as the shutdown voltage and 32kOhm as RUV2, then RUV1 can be calculated like this

-EL

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LM5116: UVLO Calculation and output results