LM3670-ADJ Potential Error - 2.5V Max output voltage in WB model

Tyler Pate

Other Parts Discussed in Thread: LM3670

Greetings,

Our customer pointed out a potential error in the LM3670. In the Webench interface it looks like the max output voltage is 2.5 where the datasheet and product page suggest the output voltage can be up to 3.3V. Is this the case for the adjustable version? It is not necessarily clear in the datasheet. For the adjustable version the datasheet only specs out feedback networks up to 2.5V.

Can you help clarify this?

Thanks, Tyler Pate

over 11 years ago

0 LaRita Gwie over 11 years ago

TI__Intellectual 980 points

Hi,

Thanks for submitting the feedback. Please let me know the input voltage range and output current your customer is using so we can accurately reproduce the issue.

Regards,

LaRita Gwie

0 Wanda Garrett - WEBENCH Design Center over 11 years ago in reply to LaRita Gwie

TI__Intellectual 2360 points

Hi Tyler,

In the LM3670 product folder, the WEBENCH launch panel shows the following ranges:

Vin from 2.5V to 5.5V

Vout from 0.7V to 3.3V

Load up to 0.35A

As this is a step-down converter, the input voltage needs to be above the desired output, with a little margin (depending on the device). If you wish to create an LM3670 design with Vout=3.3V, the requested Vin will need to be at least 4V.

As LaRita noted above, if you provide the design requirements we would be glad to see why the design was not being created as expected.

0 Scott Brenneman over 11 years ago in reply to Wanda Garrett - WEBENCH Design Center

Genius 3265 points

I'm the client who found the error Tyler is reporting. I just recreated it. I set the input range as 3.5 to 4.4 V and the output as 2.8 V @ 0.2 A. The LM3670-ADJ is not found, and when I click on the button to "See Why Other Parts Were Not Found", the reason given for the LM3670-ADJ is "Output voltage not supported", and the output voltage max. is listed as 2.5 V.

Thanks,

Scott

0 LaRita Gwie over 11 years ago in reply to Scott Brenneman

TI__Intellectual 980 points

Hi Scott,

Thanks for the clarification. The max output voltage should be

Vout,max = Vin,max - Iload,max * (Rdson,PFET + Rinductor).

I have changed the max output voltage to 5.25V but it will take some time before the server is updated.

Thanks for bringing this to our attention.

LaRita

0 Scott Brenneman over 11 years ago in reply to LaRita Gwie

Genius 3265 points

Thanks LaRita!

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LM3670-ADJ Potential Error - 2.5V Max output voltage in WB model