LM5145: How LM5145 knows current sensing mode

Wenhao Wu

Part Number: LM5145

Hi Team,

While my customer is using LM5145, they have question for its current sensing mode. Whether it is Rdson current sensing mode or shunt resistor sensing mode depends on position of ILIM pin connection.

However, from the datasheet, there is no place specifying how LM5145 finds ILIM position. Could you please help clarify from internal circuit how LM5145 knows ILIM pins therefore to select current sensing mode? Thank you!

-Wenhao

over 5 years ago

0 Daniel Li14 over 5 years ago

TI__Mastermind 27470 points

Ilim is generate a OCP reference with Rilimit adding by internal current source and adding with the voltage of Rsns or Rdson. It only work when low side is on as the Function Block Diagram 8., so when OCP works, it is low voltage statues no matter customer use SW or Sense resistor.

Thanks

Daniel Li

0 Wenhao Wu over 5 years ago in reply to Daniel Li14

TI__Genius 9046 points

Hi Daniel,

The current source of ILIM pin will vary depends on current sensing mode, as below description in the datasheet;

So there must be a way for LM5145 to know it is shunt current sensing mode or Rdson sensing mode. Falsely selection of 200uA ILIM current will result in mismatch in resistance vary in shunt current sensing mode.

So could you please tell me how LM5145 is selecting current sensing mode? Thanks!

-Wenhao

0 Daniel Li14 over 5 years ago in reply to Wenhao Wu

TI__Mastermind 27470 points

wenhao:

I am checking with internal team and will give you feedback later.

Thanks

0 Daniel Li14 over 5 years ago in reply to Daniel Li14

TI__Mastermind 27470 points

Hi wenhao

the internal has a voltage comparator to compare the Isensen voltage to select the over current reference.

Thanks

0 Wenhao Wu over 5 years ago in reply to Daniel Li14

TI__Genius 9046 points

Hi Daniel,

How this mechanism is actually operating? Could you please help clarify in more detail? A simplis model is preferred. Thanks!

-Wenhao

0 Daniel Li14 over 5 years ago in reply to Wenhao Wu

TI__Mastermind 27470 points

Hi wenhao:

I don't have simplis mode. it used internal comparator to compare the SW voltage when high side is on so that it can select 100uA or 200uA Ilimit reference by a MUX. That's all I know.

Thanks

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LM5145: How LM5145 knows current sensing mode