LM43603: Resistor setting at EN pit

Martin Seeger

Other Parts Discussed in Thread: LM43603

Dear team,

we would like to use the LM43603 for a 24V > 5.2V (2A) power supply.

Regarding the resistor setting for the EN pin, the datasheet recommends to use a 1M resistor as R_ENB (see page 30).
Having an UVLO threshold around 17V would result to a 6.8M resistor for R_ENT.

Those values are very high at first sight, so my question:

Is this configuration still okay or is there a maximum value for a reliable UVLO setting?

Thanks and best regards
Martin

over 7 years ago

0 Akshay Mehta over 7 years ago

TI__Genius 15810 points

Hello,
You're right. Looks like inside the IC, there is about 1.88Mohms of impedance at the EN pin. The high value RENB resistor might skew off the hysteresis. My suggestion at this point is to use a 500kohms RENB and calculate the top. As a trade off now, your quiescent current will go up a bit and no load efficiency could look a little worse.

0 Martin Seeger over 7 years ago in reply to Akshay Mehta

TI__Expert 5381 points

Hi Akshay,
Thanks for the fast answer and the details.
We will recalc the values and check the quiescent current!
Best regards
Martin

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LM43603: Resistor setting at EN pit