LM5121: Inrush Current Limit Programming rule

James Su

Intellectual 280 points

Part Number: LM5121

For different Inrush Current Limit request , How to setting below component value ? How chose the MOSFET ?

Have any MATHCAD FILE OR EXCEL DESIGN TOOL ?

over 8 years ago

0 EricLee over 8 years ago

TI__Guru 59331 points

Hello
The 100ohm resistor and Rinrush resistor forms a resistor divider when SLOPE is grounded.
Vcsn_original * Rinrush / (Rinrush + 100) = Vcsn_modified.
Thanks

0 PYTsai over 8 years ago in reply to EricLee

TI__Genius 11735 points

Eric,

Is there any MATHCAD FILE OR EXCEL DESIGN TOOL to help customer do such calculation? thanks!

0 EricLee over 8 years ago in reply to PYTsai

TI__Guru 59331 points

Sorry, I don't have it.

0 James Su over 8 years ago in reply to EricLee

Intellectual 280 points

Hi Eric,

please explain

Vcsn_original ：

Rinrush ：

Vcsn_modified ：

and one new question , SLCPE driver 1.2Vth NMOS True purpose ？

0 EricLee over 8 years ago in reply to James Su

TI__Guru 59331 points

1.2Vth NMOS turns off Rinrush pull-down switch when SLOPE =1.2V

0 James Su over 8 years ago in reply to EricLee

Intellectual 280 points

Hi Eric,
please explain , can't not find it in spec,
Vcsn_original ：
Rinrush ：
Vcsn_modified ：
Spec page 37 , LIN_EQ :

0 EricLee over 8 years ago in reply to James Su

TI__Guru 59331 points

Hello

The meaning is that the original CSN pin voltage (Vcsn_original) will be changed to 'Vcsn_modified' by using resistor divider.

Rirush is the resistor in the Figure 36 and 37, which forms a resistor divider.

Thanks

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LM5121: Inrush Current Limit Programming rule