20V 4A output from LM2679−ADJ

Truman Nwankwo

Other Parts Discussed in Thread: LM2679, LM22677, LM22679

Hi All,

I am considering using LM2679−ADJ to make a portable 20V, 4A output voltage supply unit running on 24V heavy duty battery. Is this product good for it? I can see from the data sheet how to use it to make a 14.8V, 3.5A power supply unit. However, if you know another product that can handle this output with adjustable current limit feature, kindly let me know, your suggestion will be highly appreciated.

I need your suggestions and recommendations.

Regards,

Truman.

over 8 years ago

0 Frank De Stasi over 8 years ago

TI__Guru 67395 points

Based on Webench the LM2679 can not handle this much power. However, I have a design for the LM22677; attached.

I used values of 23V to 25V for your input; I do not know if these are good values for you. I encourage you to go to the TI

website and use Webench to design a solution for you based on your exact requirements.

webench_design_433359_230_349502156.pdf

0 Truman Nwankwo over 8 years ago in reply to Frank De Stasi

Prodigy 50 points

Hi Frank,

Thank you for your suggestion, what you said is correct and confirm what I thought. The LM22677 is good but lacks an adjustable current limit functionality which I need for my application. Do you have idea of any similar product with this feature I can use? I wait for your response.

0 Truman Nwankwo over 8 years ago in reply to Frank De Stasi

Prodigy 50 points

Hi Frank,
I think LM22679 will be better since it has adjustable current limit feature. Let me know what you think. Secondly, the voltage at Pin 5, that is current limit adjust pin, should not exceed 0.8V to set the maximum current required, right?

0 Frank De Stasi over 8 years ago in reply to Truman Nwankwo

TI__Guru 67395 points

I would check with Webench to be sure the the LM22679 is OK. When I tried it the junction temp was too high.

Regarding the current limit adjust; the voltage on this pin is typically 0.8V. You should not force a voltage of this pin.

The device measures the current through the resistor that you hang on the pin to set the current limit.

0 Truman Nwankwo over 8 years ago in reply to Frank De Stasi

Prodigy 50 points

I did notice that. I am now considering TPS40170QRGYRQ1 . Let me know which one is best for this.

0 Frank De Stasi over 8 years ago in reply to Truman Nwankwo

TI__Guru 67395 points

I am not familiar with the TPS device. I would rely on Webench to make the best choice for you.

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20V 4A output from LM2679−ADJ