LM43603 - High resistance value for Webench interactive design

Gabriel Tremblay

Other Parts Discussed in Thread: LM43603-Q1

HI,

I use the webench to have a recommended circuit whit simulation of the LM43603-Q1. My main entry is 12.3V for Vin Min, 16 V for Vin max et 5V@2.3A for the output. For that, I got a value of 1 MOhm Rfbt and 255KOhm. Is not a little bit high.

On my side, I begin a design base on the datasheet checking the recommended value and the typical design and I got resistor value in the hundred of kOhm who fit with the recommended value.

Why Webench give me so high value?

Also, I try to edit the schematic with my own value to see the behavior of my circuit, but after finshing the edit, I lost all the simulation type (Bode Plot, steady state and transient).

Do we have a way to keep the simulation type with the edit design instead having the choice to plot only the probe?

Thanks

over 9 years ago

0 YangZhang over 9 years ago

TI__Genius 11085 points

The 1MOhm value selection is to optimize the quiecsent current of the circuit. If it is too high in the automotive design, it is totally ok to use 100kOhm as top divider and 25.5kOhm as bottom divider. The Cff should go higher to maintain the frequency of the additional zero.

I am not sure why you lost your design with schematic value adjustment. If you still have the same issue, I can forward your question to 'Simulation Models Forum' for further assistance.

-Yang

0 Gabriel Tremblay over 9 years ago in reply to YangZhang

Prodigy 40 points

But with the 100Kohm we a better stability in hard environment (noise, temperature, magnetic field)

Thanks

0 YangZhang over 9 years ago in reply to Gabriel Tremblay

TI__Genius 11085 points

Yes, the 100kOhm does provide better noise immunity. There's no issue to use 100kOhm or even 10kOhm at the resistor divider. -Yang

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LM43603 - High resistance value for Webench interactive design