TPS40055 Short Circuit Protection resistor(RILIM) Question.

Bob Lee62837

Other Parts Discussed in Thread: TPS40055

TPS40055 Short Circuit Protection resistor(RILIM) equation is two equation expressions.
One equation is from the datasheet equation 15.
Another equation is from the User's Guide(sluu190.pdf) equation 10.

Which equation Short Circuit Protection resistor?

Regard.

Bob Lee

over 13 years ago

0 Na Kong over 13 years ago

TI__Genius 17240 points

Hi Bob,

Please use the equation in the datasheet.

Regards,

0 Bob Lee62837 over 13 years ago in reply to Na Kong

Mastermind 7230 points

Dear Na,

Thank you very much for your answer.
May I ask one more question?

What is 42.86×10^-3 from the datasheet equation 15 ?

Regard.

Bob Lee

0 Na Kong over 13 years ago in reply to Bob Lee62837

TI__Genius 17240 points

Hi Bob,

The offset voltage of SW vs. ILIM in the electrical characteristics table (Vos,table) is measured at the condition of VIN = 24V, VILIM = 23.6V, i.e. there is a volage drop of 0.4V between VIN and VILIM. The second term in the equation 15 (42.86mV / Isink) removes the dependance of the comparator offset Voltage to the set-point (Vin - Vilim).

Regards,

0 Bob Lee62837 over 13 years ago in reply to Na Kong

Mastermind 7230 points

Dear Na,

Thank you very much for your answer.

Regard.

Bob Lee

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TPS40055 Short Circuit Protection resistor(RILIM) Question.